Spring Boot + Thymeleaf生成A4大小的PDF文档

1.引入相关依赖：在Maven或Gradle项目中添加Thymeleaf、Flying Saucer和OpenPDF相关依赖。可以通过以下Maven坐标或者Gradle配置添加：

<!-- Thymeleaf -->
<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>

<!-- Flying Saucer -->
<dependency>
  <groupId>org.xhtmlrenderer</groupId>
  <artifactId>flying-saucer-pdf</artifactId>
  <version>9.1.20</version>
</dependency>

<!-- OpenPDF -->
<dependency>
  <groupId>com.lowagie</groupId>
  <artifactId>itext</artifactId>
  <version>2.1.7</version>
</dependency>

2.编写PDF模板：使用Thymeleaf编写PDF模板，需要指定页面的大小为A4。样式中的@page指令用于定义页面大小和页边距，body标签中为PDF文档的主体内容。

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
  <meta charset="UTF-8">
  <title>PDF Demo</title>
  <style type="text/css">
    @page {
      
      
      size: A4;
      margin: 1cm;
    }
  </style>
</head>
<body>
  <h1 th:text="${title}">PDF Demo</h1>
  <p th:text="${content}">Hello, World!</p>
</body>
</html>

3.创建Thymeleaf模板引擎：在Spring Boot中，可以使用SpringTemplateEngine类创建Thymeleaf模板引擎。需要添加SpringResourceTemplateResolver作为模板解析器，指定模板文件的位置和前缀后缀等信息。

@Bean
public SpringTemplateEngine templateEngine() {
    
    
    SpringTemplateEngine templateEngine = new SpringTemplateEngine();
    SpringResourceTemplateResolver resolver = new SpringResourceTemplateResolver();
    resolver.setPrefix("classpath:/templates/");
    resolver.setSuffix(".html");
    resolver.setTemplateMode(TemplateMode.HTML);
    templateEngine.setTemplateResolver(resolver);
    return templateEngine;
}

4.创建PDF生成器：使用Flying Saucer和OpenPDF生成PDF文档。

@Component
public class PdfGenerator {
    
    

    private final String TEMPLATE = "pdf_template";

    private final SpringTemplateEngine templateEngine;

    @Autowired
    public PdfGenerator(SpringTemplateEngine templateEngine) {
    
    
        this.templateEngine = templateEngine;
    }

    public ByteArrayInputStream generatePdf(String title, String content) {
    
    
        // 根据 Thymeleaf 模板生成 HTML 页面
        Context context = new Context();
        context.setVariable("title", title);
        context.setVariable("content", content);
        String htmlContent = templateEngine.process(TEMPLATE, context);

        // 将 HTML 页面转换为 PDF 文档
        try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
    
    
            ITextRenderer renderer = new ITextRenderer();
            renderer.setDocumentFromString(htmlContent);
            renderer.layout();
            renderer.createPDF(baos);
            return new ByteArrayInputStream(baos.toByteArray());
        } catch (IOException | DocumentException e) {
    
    
            throw new RuntimeException(e);
        }
    }
}

5.调用PDF生成器生成PDF文档：在Controller中使用PdfGenerator生成PDF文档，并通过Response返回给前端。

@RestController
public class PdfController {
    
    

    private final PdfGenerator pdfGenerator;

    @Autowired
    public PdfController(PdfGenerator pdfGenerator) {
    
    
        this.pdfGenerator = pdfGenerator;
    }

    @GetMapping("/pdf")
    public void downloadPdf(HttpServletResponse response) throws IOException {
    
    
        response.setContentType("application/pdf");
        response.setHeader("Content-Disposition", "attachment; filename=test.pdf");

        ByteArrayInputStream bis = pdfGenerator.generatePdf("Test Title", "Test Content");
        IOUtils.copy(bis, response.getOutputStream());
    }
}

完整的示例代码可以参考下面的GitHub链接：

https://github.com/binjie09/spring-boot-pdf-demo

Spring Boot + Thymeleaf生成A4大小的PDF文档

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