How to Convert HTML to DOCX in Java

There's a far smaller audience of folks who understand the intricacies of HTML document structure than those who understand the user-friendly Microsoft (MS) Word application. Automating HTML-to-DOCX conversions makes a lot of sense if we frequently need to generate well-formatted documents from dynamic web content, streamline reporting workflows, or convert any other web-based information into editable Word documents for a non-technical business audience.

Automating HTML-to-DOCX conversions with APIs reduces the time and effort it takes to generate MS Word content for non-technical users. In this article, we'll review open-source and proprietary API solutions for streamlining HTML-to-DOCX conversions in Java, and we'll explore the relationship between HTML and DOCX file structures that makes this conversion relatively straightforward.

How Similar are HTML and DOCX Structures?

HTML and DOCX documents serve very different purposes, but they have more in common than we might initially think. They're both XML-based formats with similar approaches to structuring text on a page:

• HTML documents use an XML-based structure to organize how content appears in a web browser.
• DOCX documents use a series of zipped XML files to collectively define how content appears in the proprietary MS Word application.

Content elements in an HTML document like paragraphs (<p>), headings (<h1>, <h2>, etc.), and tables (<table>) all roughly translate into DOCX iterations of the same concept.

For example, DOCX files map HTML <p> tags to <w:p> elements, and they map <h1> tags to <w:pStyle> elements. Further, in a similar way to how HTML documents often reference CSS stylesheets (e.g., styles.css) for element styling, DOCX documents use an independent document.xml file to store content display elements and map them with Word styles and settings, stored in style.xml and settings.xml files respectively within the DOCX archive.

Differences Between HTML and DOCX to Consider

It's worth noting that HTML and DOCX files do handle certain types of content quite differently, despite sharing a similar derivative structure. Much of this can be attributed to differences between how web browser applications and the MS Word application interpret information. The challenges we encounter with HTML-to-DOCX conversions are largely driven by inconsistencies in the way custom styling, media content, and dynamic elements are interpreted.

The styling used in native HTML and native DOCX documents is often custom/proprietary, and custom/proprietary HTML styles (e.g., custom fonts) won't necessarily translate into identical DOCX styles when we convert content between those formats. Further, in HTML files, multimedia (e.g., images, videos) are included on any given page as links, whereas DOCX files embed media objects directly. Finally, the dynamic code elements we find on some HTML pages — usually written in JavaScript — won't translate to DOCX whatsoever given that DOCX is a static format.

Converting HTML to DOCX

When we convert HTML to DOCX, we effectively parse content from HTML elements and subsequently map that content to appropriate DOCX elements. The same occurs in reverse when we make the opposite conversion (a process I've written about in the past). How that parsing and mapping take place depends entirely on how we structure our code — or which APIs we elect to use in our programming project.

Open-Source Libraries for HTML-to-DOCX Conversions

If we're looking for open-source libraries to make HTML-to-DOCX conversions, we'll go a long way with libraries like jsoup and docx4j. The jsoup library is designed to parse and clean HTML programmatically into a structure that we can easily work with, and the docx4j library offers features capable of mapping HTML tags to their corresponding DOCX elements. We can also finalize the creation of our DOCX documents with docx4j, literally organizing our mapped HTML elements into a series of XML files and zipping those with a .docx extension. The docx4j library is very similar to Microsoft's OpenXML SDK, only for Java developers instead of C#.

HTML-to-DOCX Conversion Demonstration

If we're looking to simplify HTML-to-DOCX conversions, we can turn our attention to a web API solution that gets in the weeds on our behalf, parsing and mapping HTML into a consistent DOCX result without requiring us to download multiple libraries or write a lot of extra code. JitPack a free solution to use, requiring only a free API key. We'll now walk through example code that we can use to structure our API call.

To begin, we'll install the client using Maven. We'll first add the repository to our pom.xml:

<repositories>
    <repository>
        <id>jitpack.io</id>
        <url>https://jitpack.io</url>
    </repository>
</repositories>

And after that, we'll add the dependency to our pom.xml:

<dependencies>
<dependency>
    <groupId>com.github.Cloudmersive</groupId>
    <artifactId>Cloudmersive.APIClient.Java</artifactId>
    <version>v4.25</version>
</dependency>
</dependencies>

Next, we'll import the necessary classes to configure the API client, handle exceptions, etc.:

// Import classes:
//import com.cloudmersive.client.invoker.ApiClient;
//import com.cloudmersive.client.invoker.ApiException;
//import com.cloudmersive.client.invoker.Configuration;
//import com.cloudmersive.client.invoker.auth.*;
//import com.cloudmersive.client.ConvertWebApi;

Now we'll configure our API client with an API key for authentication:

ApiClient defaultClient = Configuration.getDefaultApiClient();

// Configure API key authorization: Apikey
ApiKeyAuth Apikey = (ApiKeyAuth) defaultClient.getAuthentication("Apikey");
Apikey.setApiKey("YOUR API KEY");
// Uncomment the following line to set a prefix for the API key, e.g. "Token" (defaults to null)
//Apikey.setApiKeyPrefix("Token");

Finally, we’ll create the API instance, prepare our input request, and handle our conversion (while catching any exceptions, of course):

ConvertWebApi apiInstance = new ConvertWebApi();
HtmlToOfficeRequest inputRequest = new HtmlToOfficeRequest(); // HtmlToOfficeRequest | HTML input to convert to DOCX
try {
    byte[] result = apiInstance.convertWebHtmlToDocx(inputRequest);
    System.out.println(result);
} catch (ApiException e) {
    System.err.println("Exception when calling ConvertWebApi#convertWebHtmlToDocx");
    e.printStackTrace();
}

Once our conversion is complete, we can write the resulting byte[] array to a DOCX file, and we're all finished. We can perform subsequent operations with our new DOCX document, or we can store it for business users to access directly and call it a day.

Conclusion

In this article, we reviewed some of the similarities between HTML and DOCX file structures that make converting between both formats relatively simple and easy to accomplish with code. We then discussed two open-source libraries we could use in conjunction to handle HTML-to-DOCX conversions, and we learned how to call a free proprietary API to handle all our steps in one go.