1. Overview This is the second of a series of posts about setting up a RESTful web service using Spring 3.1 with Java based configuration. The first post of the series focused on bootstrapping the web application; this post will focus on setting up REST in Spring, the Controller and HTTP response codes, configuration of payload marshalling and content negotiation. 2. Understanding REST in Spring The Spring framework supports 2 ways of creating RESTful services: using MVC with ModelAndView using HTTP message converters The ModelAndView approach is older and much better documented, but also more verbose and configuration heavy. It tries to shoehorn the REST paradigm into the old model, which is not without problems. The Spring team understood this and provided first-class REST support starting with Spring 3.0. The new approach, based on HttpMessageConverter and annotations, is much more lightweight and easy to implement. Configuration is minimal and it provides sensible defaults for what you would expect from a RESTful service. It is however newer and a a bit on the light side concerning documentation; what’s more, the Spring reference doesn’t go out of it’s way to make the distinction and the tradeoffs between the two approaches as clear as they should be. Nevertheless, this is the way RESTful services should be build after Spring 3.0. 3. The Java configuration @Configuration @EnableWebMvc public class WebConfig{ // } The new @EnableWebMvc annotation does a number of useful things – specifically, in the case of REST, it detect the existence of Jackson and JAXB 2 on the classpath and automatically creates and registers default JSON and XML converters. The functionality of the annotation is equivalent to the XML version: This is a shortcut, and though it may be useful in many situations, it’s not perfect. When more complex configuration is needed, remove the annotation and extend WebMvcConfigurationSupport directly. 4. Testing the Spring context Starting with Spring 3.1, we get first-class testing support for @Configuration classes: @RunWith( SpringJUnit4ClassRunner.class ) @ContextConfiguration( classes = { ApplicationConfig.class, PersistenceConfig.class },loader = AnnotationConfigContextLoader.class ) public class SpringTest{ @Test public void whenSpringContextIsInstantiated_thenNoExceptions(){ // When } } The Java configuration classes are simply specified with the @ContextConfiguration annotation and the new AnnotationConfigContextLoader loads the bean definitions from the @Configuration classes. Notice that the WebConfig configuration class was not included in the test because it needs to run in a servlet context, which is not provided. 5. The Controller The @Controller is the central artifact in the entire Web Tier of the RESTful API. For the purpose of this post, the controller is modeling a simple REST resource – Foo: @Controller class FooController{ @Autowired IFooService service; @RequestMapping( value = "foo",method = RequestMethod.GET ) @ResponseBody public List< Foo > getAll(){ return this.service.getAll(); } @RequestMapping( value = "foo/{id}",method = RequestMethod.GET ) @ResponseBody public Foo get( @PathVariable( "id" ) Long id ){ return RestPreconditions.checkNotNull( this.service.getById( id ) ); } @RequestMapping( value = "foo",method = RequestMethod.POST ) @ResponseStatus( HttpStatus.CREATED ) @ResponseBody public Long create( @RequestBody Foo entity ){ RestPreconditions.checkNotNullFromRequest( entity ); return this.service.create( entity ); } @RequestMapping( value = "foo",method = RequestMethod.PUT ) @ResponseStatus( HttpStatus.OK ) public void update( @RequestBody Foo entity ){ RestPreconditions.checkNotNullFromRequest( entity ); RestPreconditions.checkNotNull( this.service.getById( entity.getId() ) ); this.service.update( entity ); } @RequestMapping( value = "foo/{id}",method = RequestMethod.DELETE ) @ResponseStatus( HttpStatus.OK ) public void delete( @PathVariable( "id" ) Long id ){ this.service.deleteById( id ); } } The Controller implementation is non-public – this is because there is no need for it to be. Usually the controller is the last in the chain of dependencies – it receives HTTP requests from the Spring front controller (the DispathcerServlet) and simply delegate them forward to a service layer. If there is no use case where the controller has to be injected or manipulated through a direct reference, then I prefer not to declare it as public. The request mappings are straightforward – as with any Spring controller, the actual value of the mapping as well as the HTTP method are used to determine the target method for the request. @RequestBody will bind the parameters of the method to the body of the HTTP request, whereas @ResponseBody does the same for the response and return type. They also ensure that the resource will be marshalled and unmarshalled using the correct HTTP converter. Content negotiation will take place to choose which one of the active converters will be used, based mostly on the Accept header, although other HTTP headers may be used to determine the representation as well. 6. Mapping the HTTP response codes The status codes of the HTTP response are one of the most important parts of the REST service, and the subject can quickly become very complex. Getting these right can be what makes or breaks the service. 6.1. Unmapped requests If Spring MVC receives a request which doesn’t have a mapping, it considers the request not to be allowed and returns a 405 METHOD NOT ALLOWED back to the client. It is also good practice to include the Allow HTTP header when returning a 405 to the client, in order to specify which operations are allowed. This is the standard behavior of Spring MVC and does not require any additional configuration. 6.2. Valid, mapped requests For any request that does have a mapping, Spring MVC considers the request valid and responds with 200 OK if no other status code is specified otherwise. It is because of this that controller declares different @ResponseStatus for the create, update and delete actions but not for get, which should indeed return the default 200 OK. 6.3. Client error In case of a client error, custom exceptions are defined and mapped to the appropriate error codes. Simply throwing these exceptions from any of the layers of the web tier will ensure Spring maps the corresponding status code on the HTTP response. @ResponseStatus( value = HttpStatus.BAD_REQUEST ) public class BadRequestException extends RuntimeException{ // } @ResponseStatus( value = HttpStatus.NOT_FOUND ) public class ResourceNotFoundException extends RuntimeException{ // } These exceptions are part of the REST API and, as such, should only be used in the appropriate layers corresponding to REST; if for instance a DAO/DAL layer exist, it should not use the exceptions directly. Note also that these are not checked exceptions but runtime exceptions – in line with Spring practices and idioms. 6.4. Using @ExceptionHandler Another option to map custom exceptions on specific status codes is to use the @ExceptionHandler annotation in the controller. The problem with that approach is that the annotation only applies to the controller in which it is defined, not to the entire Spring Container, which means that it needs to be declared in each controller individually. This quickly becomes cumbersome, especially in more complex applications which many controllers. There are a few JIRA issues opened with Spring at this time to handle this and other related limitations: SPR-8124, SPR-7278, SPR-8406. 7. Additional Maven dependencies In addition to the pom.xml from the first post, two dependencies need to be added: org.codehaus.jackson jackson-mapper-asl ${jackson-mapper-asl.version} runtime javax.xml.bind jaxb-api ${jaxb-api.version} runtime 1.9.12 2.2.4 These are the libraries used to convert the representation of the REST resource to either JSON or XML. 8. Conclusion This post covered the configuration and implementation of a RESTful service using Spring 3.1 and Java based configuration, discussing HTTP response codes, basic content negotiation and marshaling. In the next articles of the series I will focus on discoverability of the API, advanced content negotiation and working with additional representations of a resource. In the meantime, check out the github project.

Being a Spring framework user and enthusiast for many years I came across several misunderstandings and problems with this stack. Also there are places where abstractions leak terribly and to effectively and safely take advantage of all the features developers need to be aware of them. That is why I am starting a Spring pitfalls series. In the first part we will take a closer look at how proxying works. Bean proxying is an essential and one of the most important infrastructure features provided by Spring. It is so important and low-level that for most of the time we don't even realize that it exists. However transactions, aspect-oriented programming, advanced scoping, @Async support and various other domestic use-cases wouldn't be possible without it. So what is proxying? Here is an example: when you inject DAO into service, Spring takes DAO instances and injects it directly. That's it. However sometimes Spring needs to be aware of each and every call made by service (and any other bean) to DAO. For instance if DAO is marked transactional it needs to start a transaction before call and commit or rolls back afterwards. Of course you can do this manually, but this is tedious, error-prone and mixes concerns. That's why we use declarative transactions on the first place. So how does Spring implement this interception mechanism? There are three methods from simplest to most advanced ones. I won't discuss their advantages and disadvantages yet, we will see them soon on a concrete examples. Java dynamic proxies Simplest solution. If DAO implements any interface, Spring will create a Java dynamic proxy implementing that interface(s) and inject it instead of the real class. The real one still exists and the proxy has reference to it, but to the outside world – the proxy is the bean. Now every time you call methods on your DAO, Spring can intercept them, add some AOP magic and call the original method. CGLIB generated classes The downside of Java dynamic proxies is a requirement on the bean to implement at least one interface. CGLIB works around this limitation by dynamically subclassing the original bean and adding interception logic directly by overriding every possible method. Think of it as subclassing the original class and calling super version amongst other things: class DAO { def findBy(id: Int) = //... } class DAO$EnhancerByCGLIB extends DAO { override def findBy(id: Int) = { startTransaction try { val result = super.findBy(id) commitTransaction() result } catch { case e => rollbackTransaction() throw e } } } However, this pseudocode does not illustrate how it works in reality – which introduces yet another problem, stay tuned. BTW all examples will be in Scala, live with that and get used to it. AspectJ weaving This is the most invasive but also the most reliable and intuitive solution from the developer perspective. In this mode interception is applied directly to your class bytecode which means the class your JVM runs is not the same as the one you wrote. AspectJ weaver adds interception logic by directly modifying your bytecode of your class, either during build – compile time weaving (CTW) or when loading a class – load time weaving (LTW). If you are curious how AspectJ magic is implemented under the hood, here is a decompiled and simplified .class file compiled with AspectJ weaving beforehand: public void inInterfaceTransactional() { try { AnnotationTransactionAspect.aspectOf().ajc$before$1$2a73e96c(this, ajc$tjp_2); throwIfNotInTransaction(); } catch(Throwable throwable) { AnnotationTransactionAspect.aspectOf().ajc$afterThrowing$2$2a73e96c(this, throwable); throw throwable; } AnnotationTransactionAspect.aspectOf().ajc$afterReturning$3$2a73e96c(this); } With load time weaving the same transformation occurs at runtime, when the class is loaded. As you can see there is nothing disturbing here, in fact this is exactly how you would program the transactions manually. Side note: do you remember the times when viruses were appending their code into executable files or dynamically injecting themselves when executable was loaded by the operating system? Knowing proxy techniques is important to understand how proxying works and how it affects your code. Let us stick with declarative transaction demarcation example, here is our battlefield: trait FooService { def inInterfaceTransactional() def inInterfaceNotTransactional(); } @Service class DefaultFooService extends FooService { private def throwIfNotInTransaction() { assume(TransactionSynchronizationManager.isActualTransactionActive) } def publicNotInInterfaceAndNotTransactional() { inInterfaceTransactional() publicNotInInterfaceButTransactional() privateMethod(); } @Transactional def publicNotInInterfaceButTransactional() { throwIfNotInTransaction() } @Transactional private def privateMethod() { throwIfNotInTransaction() } @Transactional override def inInterfaceTransactional() { throwIfNotInTransaction() } override def inInterfaceNotTransactional() { inInterfaceTransactional() publicNotInInterfaceButTransactional() privateMethod(); } } Handy throwIfNotInTransaction() method... throws exception when not invoked within a transaction. Who would have thought? This method is called from various places and different configurations. If you examine carefully how methods are invoked – this should all work. However our developers' life tend to be brutal. First obstacle was unexpected: ScalaTest does not support Spring integration testing via dedicated runner. Luckily this can be easily ported with a simple trait (handles dependency injection to test cases and application context caching): trait SpringRule extends AbstractSuite { this: Suite => abstract override def run(testName: Option[String], reporter: Reporter, stopper: Stopper, filter: Filter, configMap: Map[String, Any], distributor: Option[Distributor], tracker: Tracker) { new TestContextManager(this.getClass).prepareTestInstance(this) super.run(testName, reporter, stopper, filter, configMap, distributor, tracker) } } Note that we are not starting and rolling back transactions like the original testing framework. Not only because it would interfere with our demo but also because I find transactional tests harmful – but more on that in the future. Back to our example, here is a smoke test. The complete source code can be downloaded here from proxy-problem branch. Don't complain about the lack of assertions – here we are only testing that exceptions are not thrown: @RunWith(classOf[JUnitRunner]) @ContextConfiguration class DefaultFooServiceTest extends FunSuite with ShouldMatchers with SpringRule{ @Resource private val fooService: FooService = null test("calling method from interface should apply transactional aspect") { fooService.inInterfaceTransactional() } test("calling non-transactional method from interface should start transaction for all called methods") { fooService.inInterfaceNotTransactional() } } Surprisingly, the test fails. Well, if you've been reading my articles for a while you shouldn't be surprised: Spring AOP riddle and Spring AOP riddle demystified. Actually, the Spring reference documentation explains this in great detail, also check out this SO question. In short – non transactional method calls transactional one but bypassing the transactional proxy. Even though it seems obvious that when inInterfaceNotTransactional() calls inInterfaceTransactional() the transaction should start – it does not. The abstraction leaks. By the way also check out fascinating Transaction strategies: Understanding transaction pitfalls article for more. Remember our example showing how CGLIB works? Also knowing how polymorphism works it seems like using class based proxies should help. inInterfaceNotTransactional() now calls inInterfaceTransactional() overriden by CGLIB/Spring, which in turns calls the original classes. Not a chance! This is the real implementation in pseudo-code: class DAO$EnhancerByCGLIB extends DAO { val target: DAO = ... override def findBy(id: Int) = { startTransaction try { val result = target.findBy(id) commitTransaction() result } catch { case e => rollbackTransaction() throw e } } } Instead of subclassing and instantiating subclassed bean Spring first creates the original bean and then creates a subclass which wraps the original one (somewhat Decorator pattern) in one of the post processors. This means that – again – the self call inside bean bypasses AOP proxy around our class. Of course using CGLIB changes how are bean behaves in few other ways. For instance we can now inject concrete class rather than an interface, in fact the interface is not even needed and CGLIB proxying is required in this circumstances. There are also drawbacks – constructor injection is no longer possible, see SPR-3150, which is a shame. So what about some more thorough tests? @RunWith(classOf[JUnitRunner]) @ContextConfiguration class DefaultFooServiceTest extends FunSuite with ShouldMatchers with SpringRule { @Resource private val fooService: DefaultFooService = null test("calling method from interface should apply transactional aspect") { fooService.inInterfaceTransactional() } test("calling non-transactional method from interface should start transaction for all called methods") { fooService.inInterfaceNotTransactional() } test("calling transactional method not belonging to interface should start transaction for all called methods") { fooService.publicNotInInterfaceButTransactional() } test("calling non-transactional method not belonging to interface should start transaction for all called methods") { fooService.publicNotInInterfaceAndNotTransactional() } } Please pick tests that will fail (pick exactly two). Can you explain why? Again common sense would suggest that everything should pass, but that's not the case. You can play around yourself, see class-based-proxy branch. We are not here to expose problems but to overcome them. Unfortunately our tangled service class can only be fixed using heavy artillery – true AspectJ weaving. Both compile- and load-time weaving makes the test pass. See aspectj-ctw and aspectj-ltw branches accordingly. You should now be asking yourself several question. Which approach should I take (or: do I really need to use AspectJ?) and why should I even bother? – amongst others. I would say – in most cases simple Spring proxying will suffice. But you absolutely have to be aware of how does the propagation work and when it doesn't. Otherwise bad things happen. Commits and rollbacks occurring in unexpected places, spanning unexpected amount of data, ORM dirty checking not working, invisible records – believe, this things happen on wild. And remember that topics we have covered here apply to all AOP aspects, not only transactions. From http://nurkiewicz.blogspot.com/2011/10/spring-pitfalls-proxying.html

Most people know that you can use @Autowired to tell Spring to inject one object into another when it loads your application context. A lesser known nugget of information is that you can also use the @Value annotation to inject values from a property file into a bean’s attributes. To demonstrate this requires a few bits and pieces, including a property file: jdbc.driverClassName=oracle.jdbc.OracleDriver jdbc.url=jdbc:oracle:thin:@on-the-beach:1521:mysid jdbc.username=john jdbc.password=lennon In this example, I’ve got a some simple datasource connection details for an Oracle database, which will be injected into a fake datasource class AutowiredFakaSource: @Component public class AutowiredFakaSource { @Value("${jdbc.driverClassName}") private String driverClassName; @Value("${jdbc.url}") private String url; @Value("${jdbc.username}") private String userName; @Value("${jdbc.password}") private String password; @Value("${java.io.tmpdir}") private String tmpDir; public AutowiredFakaSource() { } public String execute() { System.out.println("Execute FakaSource"); return "A Result"; } public String getDriverClassName() { return driverClassName; } public String getUrl() { return url; } public String getUserName() { return userName; } public String getPassword() { return password; } public String getTmpDir() { return tmpDir; } } In terms of this blog, AutowiredFakaSource doesn’t really need to do anything, it just has to be a bean with some attributes. The crux of the whole thing lies in the @Value annotations: @Value("${jdbc.username}") ...which shows that a value from a property file is referenced using its name and the ${} notation. The JUnit test below demonstrates that all this works okay. @Test public void testAutowiredPropertyPlaceHolder() { System.out.println("Autowired Property PlaceHolder Test."); ApplicationContext ctx = new ClassPathXmlApplicationContext("autowired_property_place_holder.xml"); AutowiredFakaSource fakeDataSource = ctx.getBean(AutowiredFakaSource.class); assertEquals("oracle.jdbc.OracleDriver", fakeDataSource.getDriverClassName()); assertEquals("jdbc:oracle:thin:@on-the-beach:1521:mysid", fakeDataSource.getUrl()); assertEquals("john", fakeDataSource.getUserName()); assertEquals("lennon", fakeDataSource.getPassword()); assertNotNull(fakeDataSource.getTmpDir()); String expected = System.getProperty("java.io.tmpdir"); assertEquals(expected, fakeDataSource.getTmpDir()); } On last thing to note is the XML configuration file. In the example below, you can see that the XML contains two entries. The first is the PropertyPlaceholderConfigurer class that loads the properties from the jdbc.properties file and second is the XML element that enables autowiring. jdbc.properties Finally, eagle eyed readers will have spotted that the @Value annotation also allows you to load system properties. In this example I’ve loaded the Java temp directory path using: @Value("${java.io.tmpdir}") …and then tested it using the final assert in the unit test: From http://www.captaindebug.com/2011/10/autowiring-property-values-into-spring_28.html

My previous blog post discussed the use of Neo4J as a RDF triple store. Michael Hunger however informed me that the neo-rdf-sail component is no longer under active development and advised me to have a look at Tinkerpop’s Sail implementation. As mentioned in my previous blog post, I recently got asked to implement a storage and querying platform for biological RDF (Resource Description Framework) data. Traditional RDF stores are not really an option as my solution should also provide the ability to calculate shortest paths between random subjects. Calculating shortest path is however one of the strong selling points of Graph Databases and more specifically Neo4J. Unfortunately, the neo-rdf-sail component, which suits my requirements perfectly, is no longer under active development. Tinkerpop’s Sail implementation however, fills the void with an even better alternative! 1. What is Tinkerpop? Tinkerpop is an open source project that provides an entire stack of technologies within the Graph Database space. At the core of this stack is the Blueprints framework. Blueprints can be considered as the JDBC of Graph Databases. By providing a collection of generic interfaces, it allows to develop graph-based applications, without introducing explicit dependencies on concrete Graph Database implementations. Additionally, Blueprints provides concrete bindings for the Neo4J, OrientDB and Dex Graph Databases. On top of Blueprints, the Tinkerpop team developed an entire range of graph technologies, including Gremlin, a powerful, domain-specific language designed for traversing graphs. Hence, once a Blueprints binding is available for a particular Graph Database, an entire range of technologies can be leveraged. 2. Tinkerpop and Sail Last time, I talked about exposing a Neo4J Graph Database (containing RDF triples) through the Sail interface, which is part of the openrdf.org project. By doing so, we can reuse an entire range of RDF utilities (parsers and query evaluators) that are part of the openrdf.org project. The Blueprints framework provides us with a similar ability: each Graph Database binding that implements the Tinkerpop TransactionalGraph and IndexableGraph interfaces can be exposed as a GraphSail, which is Tinkerpop’s implementation of the Sail interface. Once you have your Sail available, storing and querying RDF is analogous to the piece of code shown in my previous blog article. // Create the sail graph database graph = new MyNeo4jGraph("var/flights", 100000); graph.setTransactionMode(TransactionalGraph.Mode.MANUAL); sail = new GraphSail(graph); // Initialize the sail store sail.initialize(); // Get the sail repository connection connection = new SailRepository(sail).getConnection(); // Import the data connection.add(getResource("sneeair.rdf"), null, RDFFormat.RDFXML); // Execute SPARQL query TupleQuery durationquery = connection.prepareTupleQuery(QueryLanguage.SPARQL, "PREFIX io: " + "PREFIX fl: " + "SELECT ?number ?departure ?destination " + "WHERE { " + "?flight io:flight ?number . " + "?flight fl:flightFromCityName ?departure . " + "?flight fl:flightToCityName ?destination . " + "?flight io:duration \"1:35\" . " + "}"); TupleQueryResult result = durationquery.evaluate(); The two first lines of code require some more clarification. A TransactionalGraph can be run in MANUAL or AUTOMATIC transaction mode. In AUTOMATIC mode, transactions are basically ignored, in the sense that each item that gets created is immediately persisted in the underlying Graph Database. Although this fits my needs, AUTOMATIC mode is extremely slow in case of Neo4J because of the continuous IO access. MANUAL mode on the other hand is very fast; a new transaction is created at the moment the import of the RDF data file starts and is only committed to the Neo4J data store once all RDF triples are parsed and created. Unfortunately, MANUAL mode does not scale either in my specific situation; as some of my RDF data files contain over 50 million RDF triples, they can not fit into memory (i.e. Java heap space error). Requiring fast imports, I extended the default Neo4J Blueprints binding to support intermediate commits. I based my implementation on Neo4J’s best practices for big transactions. The idea is rather simple: you specify the maximum number of items that can be kept in memory, before they should be committed to the Neo4J data store. Once this number is reached, the current transaction is committed and a new one is automatically started. Simple, but very effective! public class MyNeo4jGraph extends Neo4jGraph { private long numberOfItems = 0; private long maxNumberOfItems = 1; public MyNeo4jGraph(final String directory, long maxNumberOfItems) { super(directory, null); this.maxNumberOfItems = maxNumberOfItems; } public MyNeo4jGraph(final String directory, final Map configuration, long maxNumberOfItems) { super(directory, configuration); this.maxNumberOfItems = maxNumberOfItems; } public Vertex addVertex(final Object id) { Vertex vertex = super.addVertex(id); commitIfRequired(); return vertex; } public Edge addEdge(final Object id, final Vertex outVertex, final Vertex inVertex, final String label) { Edge edge = super.addEdge(id, outVertex, inVertex, label); commitIfRequired(); return edge; } private void commitIfRequired() { // Check whether commit should be executed if (++numberOfItems % maxNumberOfItems == 0) { // Stop the transaction stopTransaction(Conclusion.SUCCESS); // Immediately start a new one startTransaction(); } } } 3. Shortest path calculation Although Blueprints allows you to abstract away the Neo4J implementation details, it still provides you with access to the raw Neo4J data store if needed. Hence, one can still use the graph algorithms provided in the neo4j-graph-algo component to calculate shortest paths between random subjects. The complete source code can be found on the Datablend public GitHub repository.

OpenStreetMap is a global project with an aim of collaboratively collecting map data, and today Ken Guest has submitted his PHP package for communitcating with the OSM API to the public and the PEAR PEPr review process: So over the last while, I’ve been working on a PHP package imaginatively named Services_Openstreetmap, for interacting with the openstreetmap API. I initially needed it so I could search for certain POIs and tabulate the results; it’s now also capable of adding data to the openstreetmap database – nodes and other elements can be created, updated and so on. It will even access the details of the user that is being used to modify that data, which is one difference between it and the other single purpose OSM frameworks. --Ken Guest You can view the submission here, and you should definitely take a look at openstreetmap.org if you haven't already. Good news for PHP developers looking to use this project more heavily in their applications.

this article is the fourth in a series about my adventures developing a fitness tracking application with html5, play scala, coffeescript and jade. previous articles can be found at: integrating scalate and jade with play 1.2.3 trying to make coffeescript work with scalate and play integrating html5 boilerplate with scalate and play developing features after getting my desired infrastructure setup, i started coding like a madman. the first feature i needed was a stopwatch to track the duration of a workout, so i started writing one with coffeescript. after spending 20 minutes playing with dates and settimeout, i searched and found a stopwatch jquery plug-in . i added this to my app, deployed it to heroku , brought up the app on my iphone 3g, clicked start and started riding my bike to work. when i arrived, i unlocked my phone and discovered that the time had stopped. at first, i thought this was a major setback. my disappointed disappeared when i found a super neat javascript stopwatch and kåre byberg's version that worked just fine. this stopwatch used settimeout, so by keeping the start time, the app on the phone would catch up as soon as you unlocked it. i ported kåre's script to coffeescript and rejoiced in my working stopwatch. # created by kåre byberg © 21.01.2005. please acknowledge if used # on other domains than http://www.timpelen.com. # ported to coffeescript by matt raible. also added hours support. flagclock = 0 flagstop = 0 stoptime = 0 refresh = null clock = null start = (button, display) -> clock = display startdate = new date() starttime = startdate.gettime() if flagclock == 0 $(button).html("stop") flagclock = 1 counter starttime, display else $(button).html("start") flagclock = 0 flagstop = 1 counter = (starttime) -> currenttime = new date() timediff = currenttime.gettime() - starttime timediff = timediff + stoptime if flagstop == 1 if flagclock == 1 $(clock).val formattime timediff, "" callback = -> counter starttime refresh = settimeout callback, 10 else window.cleartimeout refresh stoptime = timediff formattime = (rawtime, roundtype) -> if roundtype == "round" ds = math.round(rawtime / 100) + "" else ds = math.floor(rawtime / 100) + "" sec = math.floor(rawtime / 1000) min = math.floor(rawtime / 60000) hour = math.floor(rawtime / 3600000) ds = ds.charat(ds.length - 1) start() if hour >= 24 sec = sec - 60 * min + "" sec = prependzerocheck sec min = min - 60 * hour + "" min = prependzerocheck min hour = prependzerocheck hour hour + ":" + min + ":" + sec + "." + ds prependzerocheck = (time) -> time = time + "" # convert from int to string unless time.charat(time.length - 2) == "" time = time.charat(time.length - 2) + time.charat(time.length - 1) else time = 0 + time.charat(time.length - 1) reset = -> flagstop = 0 stoptime = 0 window.cleartimeout refresh if flagclock == 1 resetdate = new date() resettime = resetdate.gettime() counter resettime else $(clock).val "00:00:00.0" @stopwatch = { start: start reset: reset } the scalate/jade template to render this stopwatch looks as follows: script(type="text/javascript" src={uri("/public/javascripts/stopwatch.coffee")}) #display input(id="clock" class="xlarge" type="text" value="00:00:00.0" readonly="readonly") #controls button(id="start" type="button" class="btn primary") start button(id="reset" type="button" class="btn :disabled") reset :plain next, i wanted to create a map that would show your location. for this, i used merge design's html 5 geolocation demo as a guide. the html5 geo api is pretty simple, containing only three methods: // gets the users current position navigator.geolocation.getcurrentposition(successcallback, errorcallback, options); // request repeated updates of position watchid = navigator.geolocation.watchposition(successcallback, errorcallback); // cancel the updates navigator.geolocation.clearwatch(watchid); after rewriting the geolocation example in coffeescript, i ended up with the following code in my map.coffee script. you'll notice it uses google maps javascript api to show an actual map with a marker. # geolocation with html 5 and google maps api based on example from maxheapsize: # http://maxheapsize.com/2009/04/11/getting-the-browsers-geolocation-with-html-5/ # this script is by merge database and design, http://merged.ca/ -- if you use some, # all, or any of this code, please offer a return link. map = null mapcenter = null geocoder = null latlng = null timeoutid = null initialize = -> if modernizr.geolocation navigator.geolocation.getcurrentposition showmap showmap = (position) -> latitude = position.coords.latitude longitude = position.coords.longitude mapoptions = { zoom: 15, maptypeid: google.maps.maptypeid.roadmap } map = new google.maps.map(document.getelementbyid("map"), mapoptions) latlng = new google.maps.latlng(latitude, longitude) map.setcenter(latlng) geocoder = new google.maps.geocoder() geocoder.geocode({'latlng': latlng}, addaddresstomap) addaddresstomap = (results, status) -> if (status == google.maps.geocoderstatus.ok) if (results[1]) marker = new google.maps.marker({ position: latlng, map: map }) $('#location').html('your location: ' + results[0].formatted_address) else alert "sorry, we were unable to geocode that address." start = -> timeoutid = settimeout initialize, 500 reset = -> if (timeoutid) cleartimeout timeoutid @map = { start: start reset: reset } the template to show the map is a mere 20 lines of jade: script(type="text/javascript" src="http://www.google.com/jsapi") script(type="text/javascript" src="http://maps.googleapis.com/maps/api/js?sensor=false") :css .demo-map { border: 1px solid silver; height: 200px; margin: 10px auto; width: 280px; } #map(class="demo-map") p(id="location") span(class="label success") new | fetching your location with html 5 geolocation... script(type="text/javascript" src={uri("/public/javascripts/map.coffee")}) :javascript map.start(); the last two features i wanted were 1) distance traveled and 2) drawing the route taken on the map. for this i learned from a simple trip meter using the geolocation api . as i was beginning to port the js to coffeescript, i thought, "there's got to be a better way." i searched and found js2coffee to do most of the conversion for me. if you know javascript and you're learning coffeescript, this is an invaluable tool. i tried out the trip meter that night evening on a bike ride and noticed it said i'd traveled 3 miles when i'd really gone 6. i quickly figured out it was only calculating start point to end point and not taking into account all the turns in between. to view what was happening, i integrated my odometer.coffee with my map using google maps polylines . upon finishing the integration, i discovered two things, 1) html5 geolocation was highly inaccurate and 2) geolocation doesn't run in the background . i was able to solve the first problem by passing in {enablehighaccuracy: true} to navigator.geolocation.watchposition(). below are two screenshots showing before high accuracy and after. both screenshots are from the same two-block walk. the second issue is a slight show-stopper. phonegap might be able to solve the problem, but i'm currently using a workaround → turning off auto-lock and keeping safari in the foreground. making it look good after i got all my desired features developed, i moved onto making the app look good. i started by using sass for my css and installed play's sass module . i then switched to less when i discovered and added twitter's bootstrap to my project. at first i used play's less module (version 0.3), but ran into compilation issues . i then tried play's greenscript module , but gave up on it when i found it was incompatible with the coffeescript module . switching back to the less module and using the "0.3.compatibility" version solved all remaining issues. you might remember that i integrated html5 boilerplate and wondering why i have both bootstrap and boilerplate in my project. at this point, i don't think boilerplate is needed, but i've kept it just in case it's doing something for html5 cross-browser compatibility. i've renamed its style.css to style.less and added the following so it has access to bootstrap's variables. /* variables from bootstrap */ @import "libs/variables.less"; then i made my app look a lot better with layouts, stylish forms , a fixed topbar and alerts . for example, here's the coffeescript i wrote to display geolocation errors: geolocationerror = (error) -> msg = 'unable to locate position. ' switch error.code when error.timeout then msg += 'timeout.' when error.position_unavailable then msg += 'position unavailable.' when error.permission_denied then msg += 'please turn on location services.' when error.unknown_error then msg += error.code $('.alert-message').remove() alert = $('') alert.html('×' + msg); alert.insertbefore($('.span10')) then i set about styling up the app so it looked good on a smartphone with css3 media queries . below is the less code i used to hide elements and squish the widths for smaller devices. @media all and (max-device-width: 480px) { /* hide scrollbar on mobile */ html { overflow-y:hidden } /* hide sidebar on mobile */ .home .span4, .home .page-header, .topbar form { display: none } .home .container { width: 320px; } .about { .container, .span10 { width: 280px; } .span10 { padding-top: 0px; } } tools in the process of developing a stopwatch, odometer, displaying routes and making everything look good, i used a number of tools. i started out primarily with textmate and its bundles for less , coffeescript and jade . when i started writing more scala, i installed the scala textmate bundle . when i needed some debugging, i switched to intellij and installed its scala plugin. coffeescript, less and haml plugins (for jade) were already installed by default. i also used james ward's setup play framework with scala in intellij . issues i think it's obvious that my biggest issue so far is the fact that a webapp can't multitask in the background like a native app can. beyond that, there's accuracy issues with html5's geolocation that i haven't seen in native apps. i also ran into a caching issue when calling getcurrentposition(). it only worked the first time and i had to refresh my browser to get it to work again. strangely enough, this only happened on my desktop (in safari and firefox) and worked fine on my iphone. unfortunately, it looks like phonegap has issues similar to this. my workaround for no webapp multitasking is turning off auto-lock and leaving the browser in the foreground while i exercise. the downside to this is it really drains the battery quickly (~ 3 hours). i constantly have to charge my phone if i'm testing it throughout the day. the testing is a real pain too. i have to deploy to heroku (which is easy enough), then go on a walk or bike ride. if something's broke, i have to return home, tweak some things, redeploy and go again. also, there's been a few times where safari crashes halfway through and i lose all the tracking data. this happens with native apps too, but seemingly not as often. if you'd like to try the app on your mobile phone and see if you experience these issues, checkout play-more.com . summary going forward, there's still more html5 features i'd like to use. in particular, i'd like to play music while the fitness tracker is running. i'd love it if cloud music services (e.g. pandora or spotify) had an api i could use to play music in a webapp. soundcloud might be an option, but i've also thought of just uploading some mp3s and playing them with the tag. i've really enjoyed developing with all these technologies and haven't experienced much frustration so far. the majority has come from integrating scalate into play, but i've resolved most problems. next, i'll talk about how i've improved play's scalate support and my experience working with anorm . source: http://raibledesigns.com/rd/entry/developing_with_html5_coffeescript_and

Let’s say you are using some external components in your web page that renders a button as below: The above code will call the delete() method when user clicks on the button. But, what if you want to show a confirmation box before calling the delete()? Since the code is rendered by a external component, most probably you won’t be having control over how its code generated. So, you have to intercept the onclick event and block it until your method is called and then invoke the original method. Lets do it.. var btn = $("#btn"); btn.data("funcToCall", btn.attr("onclick")); $("#btn").removeAttr("onclick"); $("#btn").bind("click", function(e){ if(confirm("Are you sure?")){ var func = $(this).data("funcToCall"); eval(func); } }); As you can see, the onclick function is first stored into that element and then the onclick attribute is removed. Finally when the button in clicked, our custom method is called first and based on the user decision, the delete() method is either called or not called. From http://veerasundar.com/blog/2011/10/intercepting-onclick-event-in-javascript-using-jquery/

I had to answer the following question: Shall we use a Portal and if yes, should it be Liferay Portal or Oracle Portal? Or shall we use just one or more Java web frameworks? This article shows my result. I had to look especially at Liferay and Oracle products, nevertheless the result can be used for other products, too. The short answer: A Portal makes sense only in a few use cases, in the majority of cases you should not use one. In my case, we will not use one. What is a Portal? It is important to know that we are talking about an Enterprise Portal. Wikipedia has a good definition: „An enterprise portal [...] is a framework for integrating information, people and processes across organizational boundaries. It provides a secure unified access point, often in the form of a web-based user interface, and is designed to aggregate and personalize information through application-specific portlets.“ Several Portal server are available in the Java / JVM environment. Liferay Portal and GateIn Portal (former JBoss Portal) are examples for open source products while Oracle Portal or IBM WebSphere Portal are proprietary products. You develop Portlets („simple“ web applications) and deploy them in your portal. If you need to know more about a Portal or the Portlet JSR standards, ask Wikipedia: http://en.wikipedia.org/wiki/Portlet. Should we use a Portal or not? I found several pros and cons for using a Portal instead of just web applications. Disadvantages of using a Portal: Higher complexity Additional configuration (e.g. portlet.xml, Portal server) Communication between Portlets using Events is not trivial (it is also not trivial if two applications communicate without portlets, of course) Several restrictions when developing a web application within a Portlet Additional testing efforts (test your web applications and test it within a Portal and all its Portal features) Additional costs Open source usually offers enterprise editions which include support (e.g. Liferay) Proprietary products have very high initial costs. Besides, you need support, too (e.g. Oracle) You still have to customize the portal and integrate applications. A portal product does not give you corporate identity or systems integration for free. Software licensing often is only ten percent of the total price. Developers need additional skills besides using a web framework Several restrictions must be considered choosing a web-framework and implement the web application Rethinking about web application design is necessary Portlets use other concepts such as events or an action and render phase instead of only one phase Frameworks (also called bridges) help to solve this problem (but these are standardized for JSF only, a few other plugins are available, e.g. for GWT or Grails) Actually, IMO you have to use JSF if you want to realize Portlets in a stable, relatively „easy“ and future-proof way. There is no standard bridge for other frameworks. There are no books, best practices, articles or conference sessions about Portlets without JSF, right? Advantages of using a Portal Important: Many of the pros can be realized by oneself with relatively low efforts (see the "BUT" notes after each bullet point). Single Sign On (SSO) BUT: Several Java frameworks are available, e.g OpenSSO (powerful, but complicated) or JOSSO (not so powerful, but easy to use). Good products are available, e.g. Atlassian Crowd (I love Atlassian products such as Crowd, Jira or Confluence, because they are very intuitive and easy to use). Integration of several applications within one GUI A portal gives you layout and sequence of the applications for free (including stuff such as drag & drop, minimizing windows, and so on) Communication between Portlets (i.e. between different applications) BUT: This is required without a portal, too. Several solutions can be used, such as a database, messaging, web services, events, and so on. Even „push“ is possible for some time now (using specific web framework features or HTML 5 websockets). Uniform appearence BUT: CSS can solve this problem (the keyword „corporate identity“ exists in almost every company). Create a HTML template and include your applications within this template. Done. Personalization Regarding content, structure or graphical presentation Based on individual preferences or metadata BUT: Some of these features can be realized very easily by oneself (e.g. a simple role concept). Nevertheless, GUI features such as drag & drop are more effort (although component libraries can help you a lot). Many addons are included Search Content management Document management Web 2.0 tools (e.g. blogs or wikis) Collaboration suites (e.g. team pages) Analytics and reporting Development platforms BUT: A) Do you really need these Features? B) Is the offered functionality sufficent? Portals only offer „basic“ versions of stand-alone products. For instance, the content management system or search engine of a Portal is less powerful than other „real“ products offering this functionality. Thus, you have to think about the following central question: Do we really need all those features offered by a portal? Conclusion: The total cost of ownership (TCO) is much higher when using a portal. You have to be sure, that you really need the offered features. In some situations, you can defer your decision. Create your web applications as before. You can still integrate them in a Portal later, if you really need one. For instance, the following Oracle blog describes how you can use iFrames to do this: http://blogs.oracle.com/jheadstart/entry/integrating_a_jsf_application If you decide to use a Portal, you have to choose a Portal product. Should we use an Open Source or Proprietary Portal Product? Both, open source and proprietary Portal products have pros and cons. I especially looked at Oracle Portal and Liferay Portal, but probably most aspects can be considered when evaluating other products, too. Advantages of Oracle Portal Oracle offers a full-stack suite for development (including JSF and Portlets): Oracle Application Development Framework (ADF) Oracle JDeveloper offers good support for ADF. Everything from one product line increases efficiency (database, application server, ESB, IDE, Portal, …) – at least in theory :-) Disadvantages of Oracle Portal: High initial costs (I heard something about 200K in our company) Complex, heavyweight product (compared to Liferay Portal) Proprietary Communication between Portlets is not implemented using the standard JSR-286, but a custom proprietary solution (Source: http://www.contribute.be/web/contribute/news/-/journal_content/56_INSTANCE_pdF5/10234/21893) Advantages of Liferay Portal: Open source Drastically lower initial costs Lightwight product (1-Click-Install, etc.) Disadvantages of Liferay Portal: Not everything is from one product line (this cannot be considered as disadvantage always, but in our case the customer preferred very few different vendors (keyword “IT consolidation”) Portlets are still Portlets. Although Liferay is lightweight, realizing Portlets still sucks as it does with a proprietary product When to use a Portal? Well, the conclusion is difficult. In my opinion, it does make sense only in a few use cases. If you really need many or all of those Portal features, and they are also sufficient, then use a Portal product. Though, usually it is much easier to create a simple web application which integrates your applications. Use a SSO framework, create a template, and you are done. Your developers will appreciate not to work with Portlets and its increased complexity and restrictions. Did I miss any pros or cons? Do you have another opinion (probably, many people do???), then please write a comment and let’s discuss… Best regards, Kai Wähner (Twitter: @KaiWaehner) [Content from my Blog: Kai Wähner's Blog: Pros and Cons - When to use a Portal and Portlets instead of just Java Web-Frameworks]

If your Spring beans need access to an object that is not created by Spring itself, you can “inject” it into the context by using a static parent context and registering the object with it. Beans can then reference it just as if it was defined in the application context file. Java: Configure ApplicationContext with an Injected Bean import org.springframework.context.ApplicationContext; import org.springframework.context.support.FileSystemXmlApplicationContext; import org.springframework.context.support.GenericApplicationContext; import org.springframework.context.support.StaticApplicationContext; Object externalyDefinedBean = ...; GenericApplicationContext parentContext = new StaticApplicationContext(); parentContext.getBeanFactory().registerSingleton("injectedBean", externalyDefinedBean); parentContext.refresh(); // seems to be required sometimes ApplicationContext context = new FileSystemXmlApplicationContext(springConfigs, parentContext); Xml: Make Use of It Viola! From http://theholyjava.wordpress.com/2011/10/11/spring-make-an-externally-created-object-available-to-beans-in-applicationcontext-xml/

This may not be strictly true, but it seems to me that the Guy’s at Spring are always banging on about AspectJ and Aspect Oriented Programming (AOP), to the point where I suspect that it’s used widely under the hood and is an integral part of Spring and I say “widely used under the hood”, because I haven’t come across too many projects that do use AspectJ or AOP in general. I suspect that part of the reason for this is possibly down to the fact that AOP different is a concept to Object Oriented Programming (OOP). AOP, they say, is all to do with an application’s cross-cutting concerns, which translates to mean stuff that’s common to all classes within your application. The usual example given here is logging and example code usually demonstrates logging all method entry and exit details, which is something that I’ve never found that useful. The other reason that I’ve not seen it used is that the AspectJ documentation is a bit ropey. Today’s blog is a demonstration of how to implement AspectJ’s @AfterThrowing advice in a Spring application. The idea of the after throwing advice is that you intercept an exception after it’s thrown, but before it’s caught - as shown in this rather simplistic diagram: I said above that the AOP sample code usually demonstrates logging, and in that respect this blog is no different. The idea in this contrived scenario is to log to a simple Apache Commons log any exceptions thrown. The class that actually does all this is IncidentThrowsAdvice: @Aspect public class IncidentThrowsAdvice { // Obtain a suitable logger. private static Log logger = LogFactory.getLog(IncidentThrowsAdvice.class); /** * Called between the throw and the catch */ @AfterThrowing(pointcut = "execution(* *(String, ..))", throwing = "e") public void myAfterThrowing(JoinPoint joinPoint, Throwable e) { System.out.println("Okay - we're in the handler..."); Signature signature = joinPoint.getSignature(); String methodName = signature.getName(); String stuff = signature.toString(); String arguments = Arrays.toString(joinPoint.getArgs()); logger.info("Write something in the log... We have caught exception in method: " + methodName + " with arguments " + arguments + "\nand the full toString: " + stuff + "\nthe exception is: " + e.getMessage(), e); } } The class itself is fairly straight forward. It has one method myAfterThrowing(...), which takes two arguments of type: JoinPoint and Throwable. Taking each of these in turn, JoinPoint just an class that holds information that describes a point within your code. Applying it to this particular after throwing advice means that it’s the point in your code where the exception occurred. The second argument is more straight forward as it’s the actual exception that’s currently being thrown There are two annotations applied to this class: @Aspect and @AfterThrowing. @Aspect marks the AnyOldExampleBean class as an AspectJ class, whilst the second annotation: @AfterThrowing is more interesting. This annotation tells AspectJ to call the myAfterThrowing() method when an exception occurs. It has two attributes, pointcut and throwing. pointcut defines the circumstances in which the myAfterThrowing() method is called as defined by the expression * *.*(..). This, like the rest of AspectJ seems remarkably badly documented, however you can determine that this signifies a method signature. In this case we’re checking every method in every class. This expression breaks down as follows: * - The first star is method visibility and or the method return type. The following will work in this example: * public void void whereas public on its own throws a BeanCreationException exception when loading the Spring config. *.* - this represents the package and method, again, using the same wild card formatting; hence, the following are all valid: example_10_annotations.afterthrowing_annotation.Sneeze.sneeze *.* *.sneeze example_10_annotations.*.Sneeze.sneeze ...however, example_10_annotations.*.sneeze won’t match for some reason... (..) - Defines the method arguments. In this example, the following will match: (..) (String, String, int) (String, ..) Having defined an AspectJ after throwing advice, the next step is to integrate it into the Spring application and this is a matter of adding one line to your Spring config file together with the appropriate schema reference in your : XML element: The important line in this file is: ...as it switches AOP on. The bean definitions that follow it demonstrate how the after throws advice works. The Sneeze class simply throws an exception when its called and the AnyOldExampleBean is a simple test class that calls Sneeze.sneeze(...) as shown below: public class Sneeze { /** * Throw an exception */ public void sneeze(String arg0, String arg1, int i) throws Exception { throw new Exception("Simulate an error"); } } public class AnyOldExampleBean { private Sneeze sneeze; /** * @return */ public Sneeze getSneeze() { return sneeze; } /** * @param sneeze */ public void setSneeze(Sneeze sneeze) { this.sneeze = sneeze; } /** * Do something * * @return */ public void run() { try { sneeze.sneeze("arg0", "arg1", 42); } catch (Exception e) { System.out.println("Caught e"); } finally { System.out.println("the end..."); } } } The code to run the above is: ApplicationContext ctx = new ClassPathXmlApplicationContext("example10_throwsadvice.xml"); AnyOldExampleBean myExampleBean = ctx.getBean(AnyOldExampleBean.class); myExampleBean.run(); ...and when running this code, you should get the following output: This is the after throwing exception handler 13:41:46,399 INFO ClassPathXmlApplicationContext:456 - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@4ce2cb55: startup date [Sun Aug 14 13:41:46 BST 2011]; root of context hierarchy 13:41:46,462 INFO XmlBeanDefinitionReader:315 - Loading XML bean definitions from class path resource [example10_throwsadvice.xml] 13:41:46,863 INFO DefaultListableBeanFactory:555 - Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@663257b8: defining beans [org.springframework.aop.config.internalAutoProxyCreator,exceptionHandler,example_10_annotations.afterthrowing_annotation.AfterThrowingBean#0,sneeze]; root of factory hierarchy Okay - we're in the handler... 13:41:47,171 INFO IncidentThrowsAdvice:42 - Write something in the log... We have caught exception in method: sneeze with arguments [arg0, arg1, 42] and the full toString: void example_10_annotations.afterthrowing_annotation.Sneeze.sneeze(String,String,int) the exception is: Simulate an error java.lang.Exception: Simulate an error at example_10_annotations.afterthrowing_annotation.Sneeze.sneeze(Sneeze.java:20) at example_10_annotations.afterthrowing_annotation.Sneeze$$FastClassByCGLIB$$5c47789.invoke() at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:149) at org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation.invokeJoinpoint(Cglib2AopProxy.java:688) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150) at org.springframework.aop.aspectj.AspectJAfterThrowingAdvice.invoke(AspectJAfterThrowingAdvice.java:55) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172) at ...THE REST HAS BEEN REMOVED FOR CLARITY... Caught e the end... As I said above, AspectJ seems very badly documented as can be borne out by the JavaDocs, which if you look through means that the code contains very little documentation, which in turn means that I’m glad I’m not working on it... Finally, in covering the after throwing advice, this blog only really touches on AspectJ and there are other useful AspectJ advice annotations that I will probably be covering in the near future. From http://www.captaindebug.com/2011/09/using-aspectjs-afterthrowing-advice-in.html

This tutorial will walk through out how to add a tooltip to a Grid Header.

Everyone in the Java world seems to use various opensource libraries and frameworks... and why not, there are hundreds available covering virtually every type of programming problem you’re likely to come across in today’s programming landscape. This blog takes a quick look at the reasons for using opensource artifacts and examines what could go wrong... The first reason for using them is reduced cost as it’s cheaper for your project to grab hold of an opensource library than it is for your to write the same thing yourself. The second reason for using opensource artifacts is reduced cost: you get free support from a bunch of capable and enthusiastic developers, usually in the form of copious amounts of documentation and forums. The third reason is reduced cost: you get free updates and enhancements from the opensource community and free bug fixes, although you don’t get to choose which enhancements are added to the project. Some projects, such as Tomcat, have a mechanism for voting on what enhancements are made, but at the end of the day it’s down to what really interests the developers. There are also a couple of unspoken reasons for using popular opensource libraries and frameworks: firstly, they make your CV look good. If opensource X is popular and you put that on your CV then your chances of getting a pay rise or a better job will improve. Secondly, if you work on one of the opensource projects, then you’ll earn some kudos, which, again, makes your CV look good improves the chances of you increasing the size of your pay-packet. There is an obvious downside to using opensource artifacts and that is all projects have an natural life-cycle. New versions of libraries are released, old libraries are deprecated, falling out of use because the technology’s too old, the developers have lost interest or moved on, or the rest of the community found something else that’s better and jumped on that bandwagon deserting yours. So, the problems of finding yourself saddled with retired and deprecated opensource libraries are firstly extra cost: there’s no support, no forum and no bug fixes. You’re on your own. You can often manage to download the source code to retired projects and support it yourself, but that’s not guaranteed and that costs money. The second problem of using deprecated code is extra cost: old code usually encompasses obsolete architecture and patterns, which contain known flaws and problems - after all, that’s why they’re obsolete. Using obsolete patterns and architecture encourages and in some cases forces developers to write bad code, not because your developers are bad, but that’s just the way it is... For example, there are some very obsolete JSP tags that blatantly mix database calls with business and presentation logic, which is a well know way of producing crumby, unmaintainable, spaghetti code. The third problem is, believe it or not, extra cost: I’ve recently come across a project where the code is so old that there are JAR file clashes, with different JARs containing different versions of the same API being dragged into the classpath. Certain bits of the code use one version of the API whilst other bits use the other version. eclipse didn’t know what to make of it all. There are also hidden costs: no one in there right mind wants to work on obsolete spaghetti code - it damages moral and saps the will to live, whilst damaging your ability to find that next, more highly paid, job. Plus, when people do leave, you’ve got the extra cost of finding and training their replacements. Never forget that the best people will be the first to leave, leaving you with the less experienced developers, again driving up your cost So, what can you do when faced with obsolete opensource libraries and frameworks? 1) Do nothing, continue using the obsolete library and hope everything will be alright. 2) Scrap the whole project and start again from scratch - the Big Bang Theory. 3) Refactor vigorously to remove the obsolete opensource code. This could also be seen as a way of changing the architecture of an application, updating the programming practices of the team and improving the code and whole build process. From the above I guess that you can figure out that in my opinion I prefer option 3. Option 1 is very risky, but then again, so is option 2: starting from scratch wastes time simply re-inventing the wheel, and whilst you do that, you don’t have a product, plus you may also end up with a big a mess as you started with. Option 3 is evolution and not revolution, quite the most sensible way to go. Having said all this, I definitely won’t stop using opensource code... From http://www.captaindebug.com/2011/09/benefits-and-dangers-of-using.html

I thought that it was time to take a look at Spring’s MVC interceptor mechanism, which has been around for a good number of years and is a really useful tool.

f you want to create any of these projects listed below using Eclipse IDE, OSGi Application Project OSGi Bundle Project OSGi Composite Bundle Project OSGi Fragment Project Blueprint File you need to have IBM Rational Development Tools for OSGi Applications installed. Why do we need these tools? Create and edit OSGi bundles, composite bundles, bundle fragments, and applications. Import and export OSGi bundles, composite bundles, bundle fragments, and applications. Convert existing Java Enterprise Edition (Java EE) web, Java Persistence Application (JPA), plug-in, or simple Java projects into OSGi bundles. Edit OSGi bundle, application, and composite bundle manifest files. Create and edit OSGi blueprint configuration files. Edit OSGi blueprint binding configuration files. Diagnose and fix problems in your bundles and applications using validation and quick fixes. Eclipse Plugin Installation Before you install the tools, you must have the Eclipse Helios v3.6.2 package, Eclipse IDE for Java EE Developers installed. 1. Click on Help > Install New Software 2. Point to this update site – http://public.dhe.ibm.com/ibmdl/export/pub/software/rational/OSGiAppTools – and click on Add. 3. You’ll see a list of tools – OSGi Application Development Tools, OSGi Application Development Tools UI, OSGi context-sensitive help, OSGi Help documentation, Rational Development Tools for OSGi Applications help documentation. Select all those are listed (you can ignore help stuff) and go ahead with the installation. As of writing this, the development tools’ version is 1.0.3. Maven Integration If you want to manage any of these OSGi projects using Maven, you can right-click on it and select Maven > Enable Dependency Management. You need to have Maven Integration for Eclipse(m2e) installed for this which you can find in Eclipse Marketplace. If you use Maven, you can try using the plugins provided by Apache Felix project for bundling (building an OSGi bundle). More on this plugin @ http://felix.apache.org/site/apache-felix-maven-bundle-plugin-bnd.html, http://felix.apache.org/site/apache-felix-maven-osgi-plugin.html References: http://www.ibm.com/developerworks/rational/downloads/10/rationaldevtoolsforosgiapplications.html#download From http://singztechmusings.wordpress.com/2011/09/12/creating-osgi-projects-using-eclipse-ide-and-maven/

This blog comes as an answer to a question from a reader. Now, as a rule, I don’t do request blogs, but I thought that this sounded like an interesting topic. The question refers to my blog from July 11 on accessing request parameters using Spring 3 MVC and was “Do you know how to encode the uuid so it is not visible to the user for security concerns?”. The answer is “Yes”, but that would make for a very short blog. In this case I’m assuming that the question is talking about using RESTful URLs to maintain session state information between pages. REST is a subject that’s had many words written about it, but putting it in very simplistic terms I’m defining it as not storing session or state information on your web server between browser calls. Even more simply put, it means not using the HttpSession interface implementations. Not maintaining state on the server gives you at least two obvious benefits; the first being improved loading. This is because your server is not using memory for storing state data which may, or may not be needed. The second benefit is scaling. If you’re using a domain with multiple servers, then tying session state to one server is problematic as you can’t usually guarantee that subsequent sequential calls to the domain will be directed to the same physical server. There are various techniques use to solve this problem, including making everything form based and storing state information in hidden fields, using cookies, and manipulating URLs. This blog demonstrates the third technique of encrypting state data and tagging it onto the end of a URL, so that it’s passed back and forth between the browser and the server as a request parameter: http://www.mywebsite.com/thepageIwant?session=ThisIsEncodedData An example scenario for this technique would an e-commerce site. In this case, you’d select a couple of items and add them to your basket. You’d then login and review your basket and then perhaps modify the delivery address before proceeding to pay. In doing all this, you conceptually remain logged in to the server but, in the RESTful world, the server doesn’t remember you. This example uses three screens to demonstrate this idea. The first screen logs you in, the second contains a URL that includes some session data, and the third displays the session data for review. The screen shot above shows a simple login screen. Note that I’ve used a clear text password for demonstration purposes only. The second screen in this scenario is the one that contains the encrypted session information; namely the user name and password, which has both been displayed and glued on to the end of the href of an anchor tag. The last screen shows the decoded session information demonstrating that we’ve still got it and that it’s correct. Moving on to the actual Java code for this demo... The simple bean below I’ve called Session and it holds all the state data we want encoding. public class Session { private static final String SEP = "=/="; private String name; private String password; public Session() { // Blank } public Session(String combined) { String[] split = combined.split(SEP); name = split[0]; password = split[1]; } public String getName() { return name; } public void setName(String username) { this.name = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } @Override public String toString() { return name + SEP + password; } } If you look at the code above, you’ll see that it contains two features that give it context in the application. The toString(...) returns a string that the application can encode and the single argument constructor can create a full bean from its argument. This works cohesively with the controller code, which is shown below... @Controller public class RewriteController { private static final String ENCODING_KEY = "ThisWillBeTheKey"; /** * Create the initial blank form */ @RequestMapping(value = "/loginform", method = RequestMethod.GET) public String getCreateForm(Model model) { model.addAttribute("Session", new Session()); return "login.page"; } /** * This is where you login... */ @RequestMapping(value = "/login", method = RequestMethod.POST) public String login(Session userDetails, Model model) throws UnsupportedEncodingException { byte[] encodedBytes = encodeURL(userDetails); String encodedURL = new String(Base64.encodeBase64(encodedBytes)); model.addAttribute("encodedURL", encodedURL); return "display.encoded.url"; } private byte[] encodeURL(Session userDetails) throws UnsupportedEncodingException { RC4Lite rc4 = getRC4Lite(); byte[] in = userDetails.toString().getBytes("UTF8"); byte[] out = new byte[in.length]; rc4.encrypt(in, 0, out, 0, in.length); return out; } private RC4Lite getRC4Lite() throws UnsupportedEncodingException { RC4Lite rc4 = new RC4Lite(); rc4.setKey(ENCODING_KEY.getBytes("UTF8")); return rc4; } /** * This is where you're still in the REST session and re-validate the user */ @RequestMapping(value = "/decode", method = RequestMethod.GET) public String someSessionMethod( @RequestParam(value = "session") String sessionParam, Model model) throws UnsupportedEncodingException { byte[] encodedBytes = Base64 .decodeBase64(sessionParam.getBytes("UTF8")); String decodedString = decodeURL(encodedBytes); Session session = new Session(decodedString); model.addAttribute(session); return "display.decoded.url"; } private String decodeURL(byte[] encodedBytes) throws UnsupportedEncodingException { RC4Lite rc4 = getRC4Lite(); byte[] out = new byte[encodedBytes.length]; rc4.decrypt(encodedBytes, 0, out, 0, encodedBytes.length); return new String(out); } } The controller class above contains three handler methods. The first handler method, getCreateForm(...), is fairly straight forward and simply adds a Session bean the model before displaying the login in form. The second handler method, login(...), is where all the action takes place. There are two parts to encoding the session data (the name and password). Part one is to encrypt the data and for that I’ve simply borrowed my RC4Lite class from my RC4 Encryption blog1. Once encrypted, the RC4 bytes will need converting into ASCII and for that I’ve used Apache’s Base64 class as described in my base64 blog. Converting to ASCII ensures that the characters are printable and don’t cause any problems. The string is then added to the model where it’s attached to the anchor tag as shown in the following JSP snippet: The final handler method, someSessionMethod(...) receives the input from the above link, decodes it using a reverse process to encoding It then creates a new Session object and puts that into the model, which is then displayed on the final page. Remember that this is only a sample, it just demonstrates the idea of encrypting session information and adding to a URL as a parameter. There are improvements you could make here, for example: using a interceptor to authenticate with the server upon each request before doing the business logic in the controller, or using a better encryption class, but in essence the principle applies to any webapp. There are also other techniques you can use for achieving secure web communications, so more on those later perhaps... 1 There are better ways of doing encryption than RC4, it's used here only for convenience in this demonstration. From http://www.captaindebug.com/2011/09/using-restful-urls-on-your-spring-3-mvc.html

Recently I was introduced to a project that’s already 4 months in development. After a day of coding I realized there’s something wrong with the session and transaction management. Then I found something that I’ve never used and didn’t quite know when it should be used – the EntityManager was injected into DAO objects via @PersistenceContext(type=PersistenceContextType.EXTENDED) First thing to do – google. Found this spring forum discussion, which made it clearer, but not quite. Then I started debugging and realized that the application is de-facto using the session-per-application anti-pattern. Not only that, but each DAO got its own entity manager (and underlying session) instance. An important note here – I say “entity manager and underlying session”, because Hibernate simply wraps its Session with an implementation of the standard EntityManager interface. So it makes a little difference whether we talk about entity manager or session. What happens? PerssitenceContextType.EXTENDED means that you, rather than spring, are in charge of managing your session. All spring does is create it on startup and close it on shutdown. The other option (which is the default – PerssitenceContextType.TRANSACTION) lets spring’s transaction managers create the entity manager (and session) for each request, start a transaction, and when you are finished – commit the transaction and close the session. This is called session and transaction management, and it is one of the most important things to do in a spring & JPA project. It should be done right almost from the start, so the next time you do such a project, spend extra days to get this right. But what is wrong with the above situation? Here are some effects of the extended manager: Each DAO gets a different instance of the EntityManager so you can’t do any meaningful work that involves two DAOs. If you insert a records with one EntityManager and try to use it in another one – it won’t work. The first hasn’t been flushed, and the second does not have the 1st level cache. If a session does not get closed it accumulates entities (it stores them in memory so that it doesn’t have to fetch them multiple times from the DB). Which is a pure memory leak. It is not thread-safe. The Session and EntityManager objects are not thread-safe. Since you are most likely to inject them in a singleton DAO object you will start getting weird results due to concurrent access How did this happen and why it got unnoticed for so long? I have a theory. 1. People started using the DAO layer directly from the web layer 2. Something wasn’t working for someone, so he changed the type of the persistence context, which made his code work. 3. As the project is not having many inserts, people were mainly reading data and didn’t stumble upon the various problems. 4. There hasn’t been extensive testing, with multiple people on the same instance, so the concurrency problems were not spotted. One more thing – PersistenceContextType.EXTENDED is useful in limited scenarios. The so called long-running session or session-per-conversation. When you have wizards you can have multiple requests with the same session, which saves some detaching and merging. But should you use that, make sure you don’t do it for the whole application and that you are absolutely know what you are doing. And close the session when the conversation ends. Another scenario is usage in EJB stateful beans. (In general, the extended persistence context makes more sense in a JavaEE environment) So to summarize: Spend a lot of time to properly configure session and transaction management and try to get it right Almost never use PersistenceContextType.EXTENDED in spring (outside a JavaEE container at least) Don’t use the DAO layer directly from the web layer. A base service class with wrappers for the most used operations would not be too verbose, but will save you countless headaches Code reviews should be thorough, or commit rights to core classes and configurations should be limited to a number of people that know what they are doing From http://techblog.bozho.net/?p=417

Yesterday one of my reader asked me one question that How can I set or get values from Jquery of server side element for example. So I decided to write blog post for this. This blog post is for all this people who are learning Jquery and don’t know how to set or get value for a server like ASP.NET Textbox. I know most of people know about it as Jquery is very popular browser JavaScript framework. I believe jquery as framework because it’s a single file which has lots of functionality. For this I am going to take one simple example asp.net page which contain two textboxes txtName and txtCopyName and button called copyname. On click of that button it will get the value from txtName textbox and set value of another box. So following is HTML for this. As you can see in following code there are two textbox and one button which will call JavaScript function called to CopyName to copy text from one textbox from another textbox.Now we are going to use the Jquery for this. So first we need to include Jquery script file to accomplish the task. So I am going link that jquery.js file in my header section like following. Here I have used the ASP.NET Jquery CDN. If you want know more about Jquery CDN you can visit this link. http://www.asp.net/ajaxlibrary/cdn.ashx Now it’s time to write query code. Here I have used val function to set and get value for the element. Following is the code for CopyName function. function CopyName() { var name = $("#").val(); //get value $("#").val(name); //set value return false; } Here I have used val function of jquery to set and get value. As you can see in the above code, In first statement I have get value in name variable and in another statement it was set to txtCopy textbox. Some people might argue why you have used that ClientID but it’s a good practice to have that because when you use multiple user controls your id and client id will be different. From this I have came to know that there are lots of people still there who does not basic Jquery things so in future I am going to post more post on jquery basics.That’s it. Hope you like it.

The integration framework Apache Camel already supports several important cloud services (see my overview article at http://www.kai-waehner.de/blog/2011/07/09/cloud-computing-heterogeneity-will-require-cloud-integration-apache-camel-is-already-prepared for more details). This article describes the combination of Apache Camel and the Amazon Web Services (AWS) interfaces of Simple Storage Service (S3), Simple Queue Service (SQS) and Simple Notification Service (SNS). Thus, The concept of Infrastructure as a Service (IaaS) is used to access messaging systems and data storage without any need for configuration. Registration to AWS and Setup of Camel First, you have to register to the Amazon Web Services (for free). Most AWS services include a free monthly quota, which is absolutely sufficient to play around and develop some simple applications. As its name states, AWS uses technology-independent web services. Besides, APIs for several different programming languages are available to ease development. By the way, Camel uses the AWS SDK for Java (http://aws.amazon.com/sdkforjava), of course. The documentation is detailed and easy to understand, including tutorials, screenshots and code examples . Hint 1: You should read the introductions to S3, SQS and SNS (go to http://aws.amazon.com and click on „products“) and play around with the AWS Management Console (http://aws.amazon.com/console) before you continue. This step is very easy and takes less than one hour. Then, you will have a much better understanding about AWS and where Camel can help you! Hint 2: It really helps to look at the source code of the camel-aws component, It helps you to understand how Camel uses the AWS Java API internally. If you want to write tests, you can do it the same way. In the past, I was afraid of looking at „complex“ source code of open source frameworks. But there is no need to be scared! The camel-aws component (and most other camel components) contain only of a few classes. Everything is easy to understand. It helps you to understand Camel internals, the AWS API, and to spot and solve errors due to exceptions in your code. In the meanwhile, the current Camel version 2.8 supports three AWS services: S3, SQS and SNS. All of them use similar concepts. Therefore, they are included in one single camel component: „camel-aws“. You have to add the libraries to your existing Camel project. As always, the simplest way is to use Maven and add the following dependency to the pom.xml: org.apache.camel camel-aws ${camel-version} Configuration of the Camel Endpoint The implementation and configuration of all three services is very similar. The URI looks like this (the code shows the SQS service): aws-sqs://queue-name[?options] There are two alternatives to configure your endpoint. Using Parameters The easy way is to use two paramters in the URI of your endpoint: „accessKey“ and „secretKey“ (you receive both after your AWS registration). “aws-sqs://unique-queue-name?accessKey=“INSERT_ME“&secretKey=INSERT_ME” Be aware of the following problem, which can result in a strange, non-speaking exception (thanks to Brendan Long): You’ll need to URL encode any +’s in your secret key (otherwise, they’ll be treated as spaces). + = %2B, so if your secretkey was “my+secret\key”, your Camel URL should have “secretKey=my%2Bsecret\key”. “Within the query string, the plus sign is reserved as shorthand notation for a space. Therefore, real plus signs must be encoded. This method was used to make query URIs easier to pass in systems which did not allow spaces.” Source: WC3 URI Recommendations Adding a configured AmazonClient to the Registry If you need to do more configuration (e.g. because your system is behind a firewall), you have to add an AmazonClient object to your registry. The following code shows an example using SQS, but SNS and S3 use exactly the same concept. @Override protected JndiRegistry createRegistry() throws Exception { JndiRegistry registry = super.createRegistry(); AWSCredentials awsCredentials = new BasicAWSCredentials(“INSERT_ME”, “INSERT_ME”); ClientConfiguration clientConfiguration = new ClientConfiguration(); clientConfiguration.setProxyHost(“http://myProxyHost”); clientConfiguration.setProxyPort(8080); AmazonSQSClient client = new AmazonSQSClient(awsCredentials, clientConfiguration); registry.bind(“amazonSQSClient”, client); return registry; } This example overwrites the createRegistry() method of a JUnit test (extending CamelTestSupport). You can also add this information to your runtime Camel application, of course. Apache Camel and the Simple Storage Service (S3) Simple Storage Service (S3) is a key-value-store. You can store small to very large data. The usage is very easy. You create buckets and put key-value data into these buckets. You can also create folders within buckets to organize your data. That’s it. You can monitor your buckets using the AWS Management Console – an intuitive GUI supporting most AWS services. The following example shows both alternatives for accessing the Amazon services (as described above): Paramenters and the AmazonClient. // Transfer data from your file inbox to the AWS S3 service from(“file:files/inbox”) // This is the key of your key-value data .setHeader(S3Constants.KEY, simple(“This is a static key”)) // Using parameters for accessing the AWS service .to(“aws-s3://camel-integration-bucket-mwea-kw?accessKey=INSERT_ME&secretKey=INSERT_ME&region=eu-west-1″); // Transfer data from the AWS S3 service to your file outbox from(“aws-s3://camel-integration-bucket-mwea-kw?amazonS3Client=#amazonS3Client&region=eu-wes”) .to(“file:files/outbox”); There are some additional parameters, for instance you can submit the desired AWS region or delete data after receiving it (see http://camel.apache.org/aws-s3.html and the corresponding SQS and SNS sites for more details about parameters and message headers). As you see in the code, you can use the AWS-S3 endpoint for producing and for consuming messages. Each bucket must be unique, thus you have to add some specific information such as your company to its name. Hint: If a bucket does not exist, Camel is creating it automatically (as the AWS API does). This concept is also used for SQS queues and SNS topics. Apache Camel and the Simple Queue Service (SQS) The Simple Queue Service (SQS) is similar to a JMS provider such as WebSphere MQ or ActiveMQ (but with some differences). You create queues and send messages to them. Consumers receive the messages. Contrary to most other AWS services, you cannot monitor queues by using the AWS management console directly. You have to use the service „Cloudwatch“ (http://aws.amazon.com/cloudwatch) and start an EC2 instance to monitor queues and its content. As you can see in the following code example, the syntax and concepts are almost the same as for the S3 service: from(“file:inbox”) .to(“aws-sqs://camel-integration-queue-mwea-kw?accessKey=INSERT_ME&secretKey=INSERT_ME”); from(“aws-sqs://camel-integration-queue-mwea-kw?amazonSQSClient=#amazonSQSClient”) .to(“file:outbox?fileName=sqs-${date:now:yyyy.MM.dd-hh:mm:ss:SS}”); Again, you can use the AWS-SQS endpoint for producing and for consuming messages. Each queue name must be unique. There exist two important differences to JMS (copy & paste from the AWS documentation): Q: How many times will I receive each message? Amazon SQS is engineered to provide “at least once” delivery of all messages in its queues. Although most of the time each message will be delivered to your application exactly once, you should design your system so that processing a message more than once does not create any errors or inconsistencies. Q: Why are there separate ReceiveMessage and DeleteMessage operations? When Amazon SQS returns a message to you, that message stays in the queue, whether or not you actually received the message. You are responsible for deleting the message; the delete request acknowledges that you’re done processing the message. If you don’t delete the message, Amazon SQS will deliver it again on another receive request. Apache Camel and the Simple Notification Service (SNS) The Simple Notification Service (SNS) acts like JMS topics. You create a topic, consumers subscribe to the topic and then receive notifications. Several transport protocols are supported: HTTP(S), Email and SQS. Further interfaces will be added in the future, e.g. the Short Message Service (SMS) for mobile phones. Contrary to S3 and SQS, Camel only offers a producer endpoint for this AWS service. You can only create topics and send messages via Camel. The reason is simple: Camel already offers endpoints for consuming these messages: HTTP, Email and SQS are already available. There is one tradeoff: A consumer cannot subscribe to topics using Camel – at the moment. The AWS Management Console has to be used. A very interesting discussion can be read on the Camel JIRA issue regarding the following questions: Should Camel be able to subscribe to topics? Should the producer contain this feature or should there be a consumer? In my opinion, there should be a consumer which is able to subscribe to topics, otherwise Camel is missing a key part of the AWS SNS service! Please read the discussion and contribute your opinion: https://issues.apache.org/jira/browse/CAMEL-3476. Apache Camel is already ready for the Cloud Computing Era AWS offers many more services for the cloud. Probably, it does not make sense to integrate everyone into Camel, but more AWS services will be supported in the future. For instance, SimpleDB and the Relational Database Service (RDS) are already planned and make sende, too: http://camel.apache.org/aws.html. The conclusion is easy: Apache Camel is already ready for the cloud computing era. Several important cloud services are already supported. Cloud integration will become very important in the future. Thus, Camel is on a very good way. Hopefully, we will see more cloud components, soon. I will continue to write articles about other Camel cloud components (and new AWS addons, ouf course). For instance, a component for the Platform as a Service (PaaS) product Google App Engine (GAE) is already available. If you have any additional important information, questions or other feedback, please write a comment. Thank you in advance… Best regards, Kai Wähner (Twitter: @KaiWaehner) [Content from my Blog: Cloud Integration with Apache Camel and Amazon Web Services (AWS): S3, SQS and SNS]

Varnish is a tool built to be an intermediate server in the HTTP chain, not an origin one like Apache or IIS. You can outsource caching, logging, zipping and other filters to Varnish, since they are not the main feature of an HTTP server like Apache. What we'll see today is how to work with Edge Side Includes in Varnish, as a way to compose dynamic pages from independently generated and cached fragments; we won't encounter logging or other features. If you are familiar with PHP, ESI is an (almost) standard for executing include()-like statements on a front end server like Varnish; the proxy is able not only to assembly pages but also to cache them according to different policies: a certain time, for a single user, and so on. Thijs Feryn and Alessandro Nadalin introduced me to Varnish and ESI respectively, for the first time. I recommend you to consider their blogs and talks as additional sources on these topics. Installation The default version of Varnish in Ubuntu 11.04 is instead 2.1, and apparently does not support ESI very much. Installation via packages means adding a public key and a repository to your list of software sources, and install the varnish package via apt-get or an equivalent command. You can install version 3.0.0 via packages, but only in Ubuntu LTS (10.04). A way that always works in these cases is the installation from sources. The linked page will list the package dependencies and give you a sequence of 3-4 commands to seamlessly compile varnish. I used checkinstall instead of make install to get a binary package that I can reuse later: $ sudo checkinstall -D --install=no --fstrans=no --maintainer=youraddress@gmail.com --reset-uids=yes --nodoc --pkgname=varnish --pkgversion=3.0.0 --pkgrelease=201108231000 --arch=i386 After installation with dpkg, check that varnishd is available and of the right version: [10:18:17][giorgio@Desmond:~]$ varnishd -V varnishd (varnish-3.0.0 revision 3bd5997) Copyright (c) 2006 Verdens Gang AS Copyright (c) 2006-2011 Varnish Software AS Varnish needs minimal configuration: a server to point at. For our tests you can edit /etc/varnish/default.vcl and check (or add) the following: backend default { .host = "127.0.0.1"; .port = "80"; } You can execute ps -A | grep varnishd at any time to see if varnish is already in execution. Execution [09:55:18][giorgio@Desmond:~]$ sudo varnishd -f /etc/varnish/default.vcl -s malloc,1G -T 127.0.0.1:2000 -a 0.0.0.0:8080 storage_malloc: max size 1024 MB. 1 gigabyte of memory is allocated for keeping fragments in RAM. An administrative interface will respond on port 2000, and only be accessible from localhost. http://localhost:8080/ is the exposed HTTP server, and will point to http://localhost:80 as defined in the configuration. Look at man varnishd for more switched and to man vcl for additional explanations on the configuration language. A bit of ESI ESI is a technique for leveraging HTTP cache and at the same time build dynamic pages. The problem with today's pages is that they are highly dynamic: some sections change very often or according to the current user (Welcome, John Doe or the current posts timeline); some sections do not change at all for days (the navigation bar and the layout structure); some sections change in response to external events (the list of incoming messages only when a new message arrives). It would be ideal to set different caching configurations for all the page's fragments. But implementing this strategy in the application code is error-prone and means reinventing the wheel. To use HTTP cache you will be forced to load with Ajax every single fragment of the page, even a single paragraph. With ESI, your application produces only the pieces, and lets an implementor of the Edge Side Include specification like Varnish assemble the whole thing. Example HTML page (very static): Varnish will work on this page: . PHP page (really dynamic, can change at any time): Varnish will work on this page: 2011-08-23. No sign of Varnish interventions, and totally transparent for the client. And sometimes you can also throw away Zend_Layout and similar components to assemble HTML on the PHP side.

In this blog post I am going to Explain How we create Default values for model Entities.