How to convert HTML file to PDF file in Java

With the advent of the Internet era, web pages have increasingly become the main channel for people to obtain information. However, information on web pages cannot be saved offline, and sometimes users need to view web content without a network connection. At this time, converting web pages into PDF files becomes a good choice.

Among many software, Java has relatively powerful PDF generation capabilities and provides developers with many PDF operation libraries. Below, this article will introduce how to convert HTML files to PDF files in Java.

1. Principle of converting HTML to PDF

HTML is the abbreviation of Hypertext Markup Language and is a standard markup language used to create web pages. HTML files are essentially composed of text and markup language, which can be recognized and constructed by an HTML parser to construct a rendering tree, which is ultimately displayed on the web page.

PDF (Portable Document Format) is a portable document format developed by Adobe. It can be displayed across platforms and maintain the invariance of the original content and format of the document. Unlike HTML, PDF is a static document format where the content is fixed.

Therefore, the essence of converting HTML files to PDF files is to render dynamic HTML content into static PDF documents, which needs to solve the problem of different HTML rendering trees and PDF page layouts.

2. Use iText to convert HTML to PDF

iText is a Java PDF generation library that can use Java code to generate PDF documents. The advantage of iText lies in its diverse API and wide range of applications, including PDF creation, merging, cutting, encryption, text extraction and other operations. Next, we will use the iText class library to implement the HTML to PDF function.

1. Add dependencies

First you need to add the dependency of iText class library to the project, maven:

<dependency>
   <groupId>com.itextpdf</groupId>
   <artifactId>itextpdf</artifactId>
   <version>5.5.13</version>
</dependency>

2. Write Java code and implement HTML to PDF function

The following is a Java code example:

import java.io.File;
import java.io.FileOutputStream;
import com.itextpdf.text.Document;
import com.itextpdf.text.PageSize;
import com.itextpdf.text.html.simpleparser.HTMLWorker;
import com.itextpdf.text.pdf.PdfWriter;

public class HtmlToPdfUtil {
    private static final String CHARSET = "UTF-8";

    /**
     * 将HTML内容转换为PDF文档
     * 
     * @param htmlContent HTML内容
     * @param filePath    PDF输出路径
     * @throws Exception
     */
    public static void convertHtmlToPdf(String htmlContent, String filePath) throws Exception {
        Document document = new Document(PageSize.A4, 20, 20, 20, 20);
        PdfWriter.getInstance(document, new FileOutputStream(new File(filePath)));
        document.open();
        HTMLWorker htmlWorker = new HTMLWorker(document);
        // 解析HTML文件
        htmlWorker.parse(new StringReader(htmlContent));
        document.close();
    }
}

The above code creates a PDF document object through the API provided by iText, opens the document and sets the PDF page size, and sets the PDF Output path. Then, use the parse method of the HTMLWorker class to parse and add the content in the HTML file to the PDF document, and finally close the document.

3. Summary

This article introduces how Java converts HTML files to PDF files through iText, and realizes offline saving of web page content by parsing HTML and converting it into static PDF documents. function. HTML to PDF is a commonly used document conversion method, which has practical application value for users who need to view web content in an offline environment.

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