HTML to PDF — Java

Use Case

At the beginning of the year 2020, my wife wanted to redo her CV, so I offered to give her a small tool where she had only to inform her trainings, her diplomas and her experiences and who would then put them in a document.
At first I wanted to create a document in word format, but I was not satisfied with the rendering, the HTML of the frontend looked better than the final document, that’s when I wondered if there was no way to turn this HTML into PDF.
Which led to the use of html2pdf, my frontend sent me an object corresponding to her CV and I just had to format it and generate the PDF.

HTML2PDF

The Dependency

First imported via your favorite dependency manager (here maven).

	<dependency>
	<groupId>com.itextpdf</groupId>
	<artifactId>html2pdf</artifactId>
	<version>3.0.0</version>
	</dependency>

view raw html2pdf.xml hosted with ❤ by GitHub

What is a PDF?

What is a PDF? It’s a file format, so let’s start from the beginning, create a file (thanks captain obvious).

Fill the File

To do this, nothing is simpler than to use the HtmlConverter class and its convertToPdf method which takes as a parameter :

• A String : The HTML code as a String

• An OutputStream : The PDF file.
  

  	File f = new File(fileName + ".pdf");
  	HtmlConverter.convertToPdf(html.toString(), new FileOutputStream(f));

  view raw html2pdf_createFile.java hosted with ❤ by GitHub
  In the above example, the html variable is a StringBuilder that is built by browsing the properties of a previously populated object. Warning, tags such as are not taken into account, so how to insert css?

That simple :

• Use the style property of the HTML tag

  <span style=”font-weight: bold;”>

• use tags and feed the content between the two by the content of a css file that you will read before
  

  	private void style(StringBuilder html) {
  	html.append("<style>");
  	String content = "";
  	try {
  	File file = ResourceUtils.getFile("classpath:static/bootstrap.min.css");
  	content = Files.readString(file.toPath(), StandardCharsets.UTF_8);
  	} catch (IOException e) {
  	e.printStackTrace();
  	}
  	html.append(content);
  	html.append("</style>");
  	}

  view raw html2pdf_addCss.java hosted with ❤ by GitHub
  And then use the class property of the HTML tag to add your style

  html.append("

  ")

  Warning : complex file like the Bootstrap css can produce some errors in the console of your IDE, but nothing to fear, the file will be generated anyway.

  pros and cons

  Pro

  • Easy to use.

  • Well documented.

  • Converting HTML to PDF is a fraction of the possibility of this library.

  Cons

  • Code redundancy if the object in question is already displayed on the frontend side.

  • Complex CSS files can generate console errors.

  • Maintenance difficulty in case of a large file.