Tutorial: Generating Java Files with Spring and Mustache
If you need to generate complex model from a large source data, you should try this
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Join For FreeIn this tutorial, we are going to use Spring Boot and Mustache to generate a model using a given set of data.
The data was extracted from a rules and validation table. Here's a quick explanation of how it works — we receive a request with SOAP, and we validate its structure by reading this data, for example, what type of request it is and we transform each field if necessary. The problem appears when there are many requests that we have to validate, so we need to generate and adapt a specific object for each type of request.
In this tutorial, we will create our model from a source file called data.txt, generating java files with properties and annotations in a Builder pattern structure
1. Create a Spring Boot Project in https://start.spring.io
In this tutorial, we don't need any additional dependencies except for the defaults dependencies.
2. Add the Mustache Java Library in the pom.xml File
This library works with Java 8:
XML
x
1
<dependency>
2
<groupId>com.github.spullara.mustache.java</groupId>
3
<artifactId>compiler</artifactId>
4
<version>0.9.6</version>
5
</dependency>
3. Create a Template for the Class (Builder Pattern)
Here the Mustache manual https://mustache.github.io/mustache.5.html
Java
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1
package {{packages}}
2
3
import java.io.Serializable;
4
import javax.validation.constraints.*;
5
6
/**
7
*
8
* @author Fsanmiguel
9
*/
10
public class {{classname}} implements Serializable{
11
12
private static final long serialVersionUID = {{serialVersionUID}};
13
14
{{#properties}}
15
{{#annotations}}
16
{{&.}}
17
{{/annotations}}
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private String {{property}};
19
20
{{/properties}}
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//getters
23
{{#properties}}
24
public String {{getter}}() {
25
return {{property}};
26
}
27
{{/properties}}
28
29
private {{classname}}(Builder builder){
30
{{#properties}}
31
this.{{property}} = builder.{{property}};
32
{{/properties}}
33
}
34
35
public static Builder new{{classname}}() {
36
return new Builder();
37
}
38
39
public static class Builder {
40
{{#properties}}
41
private String {{property}};
42
{{/properties}}
43
44
private Builder() {}
45
46
public {{classname}} build() {
47
return new {{classname}}(this);
48
}
49
{{#properties}}
50
public Builder with{{camelcase}}(String {{property}}) {
51
this.{{property}} = {{property}};
52
return this;
53
}
54
{{/properties}}
55
}
56
57
58
}
4. Create a Context Class to Adapt the Given Data to the Template
In this tutorial, we need a simple class that matches the template property names
Java
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1
97
1
package com.modelgenerator.modelgenerator.model;
2
3
import org.springframework.util.StringUtils;
4
5
import java.util.List;
6
7
public class Context {
8
9
List<Property> properties;
10
List<String> getters;
11
List<String> setters;
12
List<String> constants;
13
String classname;
14
String serialVersionUID;
15
String packages;
16
17
18
public List<Property> getProperties() {
19
return properties;
20
}
21
22
public void setProperties(List<Property> properties) {
23
this.properties = properties;
24
}
25
26
public String getClassname() {
27
return classname;
28
}
29
30
public void setClassname(String classname) {
31
this.classname = classname;
32
}
33
34
public String getSerialVersionUID() {
35
return serialVersionUID;
36
}
37
38
public void setSerialVersionUID(String serialVersionUID) {
39
this.serialVersionUID = serialVersionUID;
40
}
41
42
public String getPackages() {
43
return packages;
44
}
45
46
public void setPackages(String packages) {
47
this.packages = packages;
48
}
49
50
public List<String> getGetters() {
51
return getters;
52
}
53
54
public List<String> getSetters() {
55
return setters;
56
}
57
58
public void setGetters(List<String> getters) {
59
this.getters = getters;
60
}
61
62
public void setSetters(List<String> setters) {
63
this.setters = setters;
64
}
65
66
public List<String> getConstants() {
67
return constants;
68
}
69
70
public void setConstants(List<String> constants) {
71
this.constants = constants;
72
}
73
74
public static class Property {
75
String property;
76
String getter;
77
String camelcase;
78
List<String> annotations;
79
String type = "String";
80
81
public Property(String property, List<String> annotations) {
82
this.annotations = annotations;
83
this.property = property;
84
this.getter = "get"+StringUtils.capitalize(property);
85
this.camelcase = StringUtils.capitalize(property);
86
}
87
88
public Property(String property, List<String> annotations, String type) {
89
this.annotations = annotations;
90
this.property = property;
91
this.getter = "get"+StringUtils.capitalize(property);
92
this.camelcase = StringUtils.capitalize(property);
93
this.type = type;
94
}
95
}
96
}
97
5. Read and Transform the Data to the Context Class
Java
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1
122
1
package com.modelgenerator.modelgenerator;
2
3
import com.modelgenerator.modelgenerator.model.Context;
4
import com.modelgenerator.modelgenerator.model.MessField;
5
import com.github.mustachejava.DefaultMustacheFactory;
6
import com.github.mustachejava.Mustache;
7
import com.github.mustachejava.MustacheFactory;
8
import org.slf4j.Logger;
9
import org.slf4j.LoggerFactory;
10
11
import java.io.IOException;
12
import java.io.StringWriter;
13
import java.nio.file.Files;
14
import java.nio.file.Path;
15
import java.nio.file.Paths;
16
import java.nio.file.StandardOpenOption;
17
import java.text.MessageFormat;
18
import java.util.ArrayList;
19
import java.util.Arrays;
20
import java.util.List;
21
import java.util.Map;
22
import java.util.stream.Collectors;
23
24
public class ModelGeneratorApp {
25
26
private static Logger LOG = LoggerFactory
27
.getLogger(ModelGeneratorApp.class);
28
29
public static void main(String[] args) throws IOException {
30
Path data = Paths.get("./data1.txt");
31
List<String> content = Files.readAllLines(data);
32
33
//TODO fill this list with the given data
34
List<MessField> messFieldList = new ArrayList<>();
35
36
String networks [] = {"ACCL","ACCL-MLD",};
37
String messages [] = {"1A","2A","3A","4A"};
38
39
String formatClassName = "{0}{1}";
40
Arrays.asList(networks).stream()
41
.forEach(n -> {
42
Arrays.asList(messages).stream()
43
.forEach(m -> {
44
String className = MessageFormat.format(formatClassName,n,m);
45
className = className.replace("-","");
46
generateClasses(className,messFieldList,n,m );
47
});
48
});
49
}
50
51
52
public static void generateClasses(String className,
53
List<MessField> messFieldList,
54
String network,
55
String message) {
56
57
//filter the data and group by a field
58
Map<String, List<MessField>> collect = messFieldList
59
.stream()
60
.distinct()
61
.filter(s -> network.equals(s.getVi_network()))
62
.filter(s -> message.equals(s.getVi_mess_name())).
63
collect(Collectors.groupingBy(MessField::getVi_variablename));
64
65
66
Context context = new Context();
67
context.setClassname(className);
68
context.setPackages("com.modelgenerator.modelgenerator;");
69
context.setSerialVersionUID("312312412312312312L");
70
List<Context.Property> properties = collect.entrySet()
71
.stream()
72
.map(f -> new Context.Property(camelCase(f.getKey()),
73
Arrays.asList("@NotNull")))
74
.collect(Collectors.toList());
75
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context.setProperties(properties);
77
String content = mustacheContent(context, "dtotemplate.mustache");
78
generateFile(MessageFormat.format("./classes/{0}.java", className), content);
79
80
}
81
82
public static String mustacheContent(Object context, String template) {
83
try {
84
StringWriter writer = new StringWriter();
85
MustacheFactory mf = new DefaultMustacheFactory();
86
Mustache mustache = mf.compile(template);
87
mustache.execute(writer, context).flush();
88
return writer.toString();
89
} catch (Exception ex) {
90
LOG.error("mustache error", ex);
91
}
92
return "";
93
}
94
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public static void generateFile(String className, String content) {
96
LOG.info("GENERATING "+ className);
97
try {
98
Files.deleteIfExists(Paths.get(className));
99
Files.write(Paths.get(className), content.getBytes(), StandardOpenOption.CREATE_NEW);
100
} catch (IOException e) {
101
LOG.error("Error generating file", e);
102
}
103
104
}
105
106
public static String camelCase(String word) {
107
String[] chars = word.split("");
108
Boolean upper = false;
109
String results = "";
110
for (String c : chars) {
111
if (!"_".equals(c)) {
112
results += upper ? c.toUpperCase() : c;
113
upper = false;
114
} else {
115
upper = true;
116
}
117
}
118
return results;
119
}
120
121
}
122
6. Examine the Generated Objects
You can run several times until you get the Java files correctly
Here's the output:
Here's a generated Java file:
Java
x
393
1
package com.modelgenerator.modelgenerator;
2
3
import java.io.Serializable;
4
import javax.validation.constraints.*;
5
6
/**
7
*
8
* @author Fsanmiguel
9
*/
10
public class ACCL2A implements Serializable{
11
12
private static final long serialVersionUID = 312312412312312312L;
13
14
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private String destinoFondos;
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17
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private String codProcedimiento;
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20
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private String cuentaOrigen;
22
23
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private String numOrdenAch;
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26
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private String cuentaDestino;
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29
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private String origenFondos;
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32
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private String titularOriginante;
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private String codSucursalOriginante;
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38
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private String etc;
40
41
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private String codSubDestinatario;
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private String codSubOriginante;
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private String codServicio;
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50
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private String canal;
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53
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private String tipOrden;
55
56
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private String codOriginante;
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59
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private String glosa;
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62
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private String codPaisOriginante;
64
65
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private String titularDestinatario;
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68
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private String tipCuentaDestino;
70
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private String importe;
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private String numOrdenOriginante;
76
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private String ciNitOriginante;
79
80
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private String tipoDocumento;
82
83
84
private String codDestinatario;
85
86
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private String codMoneda;
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89
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private String codPaisDestinatario;
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92
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private String tipCuentaOrigen;
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private String codCamara;
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98
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private String ciNitDestinatario;
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101
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private String fecCamara;
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104
105
//getters
106
public String getDestinoFondos() {
107
return destinoFondos;
108
}
109
public String getCodProcedimiento() {
110
return codProcedimiento;
111
}
112
public String getCuentaOrigen() {
113
return cuentaOrigen;
114
}
115
public String getNumOrdenAch() {
116
return numOrdenAch;
117
}
118
public String getCuentaDestino() {
119
return cuentaDestino;
120
}
121
public String getOrigenFondos() {
122
return origenFondos;
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}
124
public String getTitularOriginante() {
125
return titularOriginante;
126
}
127
public String getCodSucursalOriginante() {
128
return codSucursalOriginante;
129
}
130
public String getEtc() {
131
return etc;
132
}
133
public String getCodSubDestinatario() {
134
return codSubDestinatario;
135
}
136
public String getCodSubOriginante() {
137
return codSubOriginante;
138
}
139
public String getCodServicio() {
140
return codServicio;
141
}
142
public String getCanal() {
143
return canal;
144
}
145
public String getTipOrden() {
146
return tipOrden;
147
}
148
public String getCodOriginante() {
149
return codOriginante;
150
}
151
public String getGlosa() {
152
return glosa;
153
}
154
public String getCodPaisOriginante() {
155
return codPaisOriginante;
156
}
157
public String getTitularDestinatario() {
158
return titularDestinatario;
159
}
160
public String getTipCuentaDestino() {
161
return tipCuentaDestino;
162
}
163
public String getImporte() {
164
return importe;
165
}
166
public String getNumOrdenOriginante() {
167
return numOrdenOriginante;
168
}
169
public String getCiNitOriginante() {
170
return ciNitOriginante;
171
}
172
public String getTipoDocumento() {
173
return tipoDocumento;
174
}
175
public String getCodDestinatario() {
176
return codDestinatario;
177
}
178
public String getCodMoneda() {
179
return codMoneda;
180
}
181
public String getCodPaisDestinatario() {
182
return codPaisDestinatario;
183
}
184
public String getTipCuentaOrigen() {
185
return tipCuentaOrigen;
186
}
187
public String getCodCamara() {
188
return codCamara;
189
}
190
public String getCiNitDestinatario() {
191
return ciNitDestinatario;
192
}
193
public String getFecCamara() {
194
return fecCamara;
195
}
196
197
private ACCL2A(Builder builder){
198
this.destinoFondos = builder.destinoFondos;
199
this.codProcedimiento = builder.codProcedimiento;
200
this.cuentaOrigen = builder.cuentaOrigen;
201
this.numOrdenAch = builder.numOrdenAch;
202
this.cuentaDestino = builder.cuentaDestino;
203
this.origenFondos = builder.origenFondos;
204
this.titularOriginante = builder.titularOriginante;
205
this.codSucursalOriginante = builder.codSucursalOriginante;
206
this.etc = builder.etc;
207
this.codSubDestinatario = builder.codSubDestinatario;
208
this.codSubOriginante = builder.codSubOriginante;
209
this.codServicio = builder.codServicio;
210
this.canal = builder.canal;
211
this.tipOrden = builder.tipOrden;
212
this.codOriginante = builder.codOriginante;
213
this.glosa = builder.glosa;
214
this.codPaisOriginante = builder.codPaisOriginante;
215
this.titularDestinatario = builder.titularDestinatario;
216
this.tipCuentaDestino = builder.tipCuentaDestino;
217
this.importe = builder.importe;
218
this.numOrdenOriginante = builder.numOrdenOriginante;
219
this.ciNitOriginante = builder.ciNitOriginante;
220
this.tipoDocumento = builder.tipoDocumento;
221
this.codDestinatario = builder.codDestinatario;
222
this.codMoneda = builder.codMoneda;
223
this.codPaisDestinatario = builder.codPaisDestinatario;
224
this.tipCuentaOrigen = builder.tipCuentaOrigen;
225
this.codCamara = builder.codCamara;
226
this.ciNitDestinatario = builder.ciNitDestinatario;
227
this.fecCamara = builder.fecCamara;
228
}
229
230
public static Builder newACCL2A() {
231
return new Builder();
232
}
233
234
public static class Builder {
235
private String destinoFondos;
236
private String codProcedimiento;
237
private String cuentaOrigen;
238
private String numOrdenAch;
239
private String cuentaDestino;
240
private String origenFondos;
241
private String titularOriginante;
242
private String codSucursalOriginante;
243
private String etc;
244
private String codSubDestinatario;
245
private String codSubOriginante;
246
private String codServicio;
247
private String canal;
248
private String tipOrden;
249
private String codOriginante;
250
private String glosa;
251
private String codPaisOriginante;
252
private String titularDestinatario;
253
private String tipCuentaDestino;
254
private String importe;
255
private String numOrdenOriginante;
256
private String ciNitOriginante;
257
private String tipoDocumento;
258
private String codDestinatario;
259
private String codMoneda;
260
private String codPaisDestinatario;
261
private String tipCuentaOrigen;
262
private String codCamara;
263
private String ciNitDestinatario;
264
private String fecCamara;
265
266
private Builder() {}
267
268
public ACCL2A build() {
269
return new ACCL2A(this);
270
}
271
public Builder withDestinoFondos(String destinoFondos) {
272
this.destinoFondos = destinoFondos;
273
return this;
274
}
275
public Builder withCodProcedimiento(String codProcedimiento) {
276
this.codProcedimiento = codProcedimiento;
277
return this;
278
}
279
public Builder withCuentaOrigen(String cuentaOrigen) {
280
this.cuentaOrigen = cuentaOrigen;
281
return this;
282
}
283
public Builder withNumOrdenAch(String numOrdenAch) {
284
this.numOrdenAch = numOrdenAch;
285
return this;
286
}
287
public Builder withCuentaDestino(String cuentaDestino) {
288
this.cuentaDestino = cuentaDestino;
289
return this;
290
}
291
public Builder withOrigenFondos(String origenFondos) {
292
this.origenFondos = origenFondos;
293
return this;
294
}
295
public Builder withTitularOriginante(String titularOriginante) {
296
this.titularOriginante = titularOriginante;
297
return this;
298
}
299
public Builder withCodSucursalOriginante(String codSucursalOriginante) {
300
this.codSucursalOriginante = codSucursalOriginante;
301
return this;
302
}
303
public Builder withEtc(String etc) {
304
this.etc = etc;
305
return this;
306
}
307
public Builder withCodSubDestinatario(String codSubDestinatario) {
308
this.codSubDestinatario = codSubDestinatario;
309
return this;
310
}
311
public Builder withCodSubOriginante(String codSubOriginante) {
312
this.codSubOriginante = codSubOriginante;
313
return this;
314
}
315
public Builder withCodServicio(String codServicio) {
316
this.codServicio = codServicio;
317
return this;
318
}
319
public Builder withCanal(String canal) {
320
this.canal = canal;
321
return this;
322
}
323
public Builder withTipOrden(String tipOrden) {
324
this.tipOrden = tipOrden;
325
return this;
326
}
327
public Builder withCodOriginante(String codOriginante) {
328
this.codOriginante = codOriginante;
329
return this;
330
}
331
public Builder withGlosa(String glosa) {
332
this.glosa = glosa;
333
return this;
334
}
335
public Builder withCodPaisOriginante(String codPaisOriginante) {
336
this.codPaisOriginante = codPaisOriginante;
337
return this;
338
}
339
public Builder withTitularDestinatario(String titularDestinatario) {
340
this.titularDestinatario = titularDestinatario;
341
return this;
342
}
343
public Builder withTipCuentaDestino(String tipCuentaDestino) {
344
this.tipCuentaDestino = tipCuentaDestino;
345
return this;
346
}
347
public Builder withImporte(String importe) {
348
this.importe = importe;
349
return this;
350
}
351
public Builder withNumOrdenOriginante(String numOrdenOriginante) {
352
this.numOrdenOriginante = numOrdenOriginante;
353
return this;
354
}
355
public Builder withCiNitOriginante(String ciNitOriginante) {
356
this.ciNitOriginante = ciNitOriginante;
357
return this;
358
}
359
public Builder withTipoDocumento(String tipoDocumento) {
360
this.tipoDocumento = tipoDocumento;
361
return this;
362
}
363
public Builder withCodDestinatario(String codDestinatario) {
364
this.codDestinatario = codDestinatario;
365
return this;
366
}
367
public Builder withCodMoneda(String codMoneda) {
368
this.codMoneda = codMoneda;
369
return this;
370
}
371
public Builder withCodPaisDestinatario(String codPaisDestinatario) {
372
this.codPaisDestinatario = codPaisDestinatario;
373
return this;
374
}
375
public Builder withTipCuentaOrigen(String tipCuentaOrigen) {
376
this.tipCuentaOrigen = tipCuentaOrigen;
377
return this;
378
}
379
public Builder withCodCamara(String codCamara) {
380
this.codCamara = codCamara;
381
return this;
382
}
383
public Builder withCiNitDestinatario(String ciNitDestinatario) {
384
this.ciNitDestinatario = ciNitDestinatario;
385
return this;
386
}
387
public Builder withFecCamara(String fecCamara) {
388
this.fecCamara = fecCamara;
389
return this;
390
}
391
}
392
393
}
Conclusion
There are situations when it becomes very repetitive to write a complete and complex model in a migration or a new implementation, and maybe the definition of each file can be structure in a source data. This is very useful and can save a lot of time.
Here the source code: https://github.com/farvher/modelgenerator
Spring Framework
Java (programming language)
Mustache (template system)
Published at DZone with permission of Farith Sanmiguel. See the original article here.
Opinions expressed by DZone contributors are their own.
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