1. Background
In some business scenarios, it is necessary to provide relevant electronic documents, such as online banking / payment treasure in the transfer of electronic receipt, signed electronic contracts. Enabling users to view, download, print. The commonly used solution is to return relevant data information, generate the corresponding pdf file to the user.
This article Source: http://git.oschina.net/lujianing/java_pdf_demo
2.iText
iText is a well-known open source sourceforge project site, is a java class library for generating PDF documents. You can generate PDF or rtf document by iText not only, but also can convert XML, Html files to PDF files.
iText official website: http://itextpdf.com/
iText development documents: http://developers.itextpdf.com/developers-home
iText There are currently two versions iText5 and iText7. iText5 should be a version with more online. iText5 because a lot of developers involved contribute code, so there is unreasonable in some specifications and design. iText7 was later officially for reconstruction iText5, the difference between the two versions is still getting bigger. However, in actual use, generally used are relatively simple, so do not stick to particular which version to use. For example, we http://mvnrepository.com/ search iText, depending iText5 are out of.
To a most simple example:
Add dependence:
<!-- https://mvnrepository.com/artifact/com.itextpdf/itextpdf -->
<dependency>
<groupId>com.itextpdf</groupId> <artifactId>itextpdf</artifactId> <version>5.5.11</version> </dependency>Test code: JavaToPdf
package com.lujianing.test;
import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Paragraph;
import com.itextpdf.text.pdf.PdfWriter; import java.io.FileNotFoundException; import java.io.FileOutputStream; /** * Created by lujianing on 2017/5/7. */ public class JavaToPdf { private static final String DEST = "target/HelloWorld.pdf"; public static void main(String[] args) throws FileNotFoundException, DocumentException { Document document = new Document(); PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(DEST)); document.open(); document.add(new Paragraph("hello world")); document.close(); writer.close(); } }operation result:
3.iText- Chinese support
iText default does not support Chinese, so you need to add the corresponding Chinese font, such as boldface simhei.ttf
Refer to the documentation: http://developers.itextpdf.com/examples/font-examples/using-fonts#1227-tengwarquenya1.java
Test code: JavaToPdfCN
package com.lujianing.test;
import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Font;
import com.itextpdf.text.FontFactory; import com.itextpdf.text.Paragraph; import com.itextpdf.text.pdf.BaseFont; import com.itextpdf.text.pdf.PdfWriter; import java.io.FileNotFoundException; import java.io.FileOutputStream; /** * Created by lujianing on 2017/5/7. */ public class JavaToPdfCN { private static final String DEST = "target/HelloWorld_CN.pdf"; private static final String FONT = "simhei.ttf"; public static void main(String[] args) throws FileNotFoundException, DocumentException { Document document = new Document(); PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(DEST)); document.open(); Font f1 = FontFactory.getFont(FONT, BaseFont.IDENTITY_H, BaseFont.NOT_EMBEDDED); document.add(new Paragraph("hello world,我是鲁家宁", f1)); document.close(); writer.close(); } }Output:
4.iText-Html rendering
In some of the more complex pdf layout, we can go through to generate pdf html
Refer to the documentation: http://developers.itextpdf.com/examples/xml-worker-itext5/xml-worker-examples
Add dependence:
<!-- https://mvnrepository.com/artifact/com.itextpdf.tool/xmlworker -->
<dependency>
<groupId>com.itextpdf.tool</groupId> <artifactId>xmlworker</artifactId> <version>5.5.11</version> </dependency> Add Template: template.html
<!DOCTYPE html>
<html lang="en"> <head> <meta charset="UTF-8"/> <title>Title</title> <style> body{ font-family:SimHei; } .red{ color: red; } </style> </head> <body> <div class="red"> 你好，鲁家宁 </div> </body> </html>Test code: JavaToPdfHtml
package com.lujianing.test;
import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.pdf.PdfWriter;
import com.itextpdf.tool.xml.XMLWorkerFontProvider; import com.itextpdf.tool.xml.XMLWorkerHelper; import com.lujianing.test.util.PathUtil; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.nio.charset.Charset; /** * Created by lujianing on 2017/5/7. */ public class JavaToPdfHtml { private static final String DEST = "target/HelloWorld_CN_HTML.pdf"; private static final String HTML = PathUtil.getCurrentPath()+"/template.html"; private static final String FONT = "simhei.ttf"; public static void main(String[] args) throws IOException, DocumentException { // step 1 Document document = new Document(); // step 2 PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(DEST)); // step 3 document.open(); // step 4 XMLWorkerFontProvider fontImp = new XMLWorkerFontProvider(XMLWorkerFontProvider.DONTLOOKFORFONTS); fontImp.register(FONT); XMLWorkerHelper.getInstance().parseXHtml(writer, document, new FileInputStream(HTML), null, Charset.forName("UTF-8"), fontImp); // step 5 document.close(); } }Output:
requires attention:
1.html must use the standard syntax, the label must require closure
2.html if there are Chinese, you need to add in the corresponding font styles styles
5.iText-Html-Freemarker rendering
In actual use, html content is dynamically rendered, so we need to add template engine support, you can use FreeMarker / Velocity, FreeMarker example used here
Add FreeMarke dependence:
<!-- https://mvnrepository.com/artifact/org.freemarker/freemarker -->
<dependency>
<groupId>org.freemarker</groupId> <artifactId>freemarker</artifactId> <version>2.3.19</version> </dependency>Add Template: template_freemarker.html
<!DOCTYPE html>
<html lang="en"> <head> <meta charset="UTF-8"/> <title>Title</title> <style> body{ font-family:SimHei; } .blue{ color: blue; } </style> </head> <body> <div class="blue"> 你好，${name} </div> </body> </html>Test code: JavaToPdfHtmlFreeMarker
package com.lujianing.test;
import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.pdf.PdfWriter;
import com.itextpdf.tool.xml.XMLWorkerFontProvider; import com.itextpdf.tool.xml.XMLWorkerHelper; import com.lujianing.test.util.PathUtil; import freemarker.template.Configuration; import freemarker.template.Template; import java.io.ByteArrayInputStream; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.StringWriter; import java.io.Writer; import java.nio.charset.Charset; import java.util.HashMap; import java.util.Map; /** * Created by lujianing on 2017/5/7. */ public class JavaToPdfHtmlFreeMarker { private static final String DEST = "target/HelloWorld_CN_HTML_FREEMARKER.pdf"; private static final String HTML = "template_freemarker.html"; private static final String FONT = "simhei.ttf"; private static Configuration freemarkerCfg = null; static { freemarkerCfg =new Configuration(); //freemarker的模板目录 try { freemarkerCfg.setDirectoryForTemplateLoading(new File(PathUtil.getCurrentPath())); } catch (IOException e) { e.printStackTrace(); } } public static void main(String[] args) throws IOException, DocumentException { Map<String,Object> data = new HashMap(); data.put("name","鲁家宁"); String content = JavaToPdfHtmlFreeMarker.freeMarkerRender(data,HTML); JavaToPdfHtmlFreeMarker.createPdf(content,DEST); } public static void createPdf(String content,String dest) throws IOException, DocumentException { // step 1 Document document = new Document(); // step 2 PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(dest)); // step 3 document.open(); // step 4 XMLWorkerFontProvider fontImp = new XMLWorkerFontProvider(XMLWorkerFontProvider.DONTLOOKFORFONTS); fontImp.register(FONT); XMLWorkerHelper.getInstance().parseXHtml(writer, document, new ByteArrayInputStream(content.getBytes()), null, Charset.forName("UTF-8"), fontImp); // step 5 document.close(); } /** * freemarker渲染html */ public static String freeMarkerRender(Map<String, Object> data, String htmlTmp) { Writer out = new StringWriter(); try { // 获取模板,并设置编码方式 Template template = freemarkerCfg.getTemplate(htmlTmp); template.setEncoding("UTF-8"); // 合并数据模型与模板 template.process(data, out); //将合并后的数据和模板写入到流中，这里使用的字符流 out.flush(); return out.toString(); } catch (Exception e) { e.printStackTrace(); } finally { try { out.close(); } catch (IOException ex) { ex.printStackTrace(); } } return null; } }Output:
So far, we have achieved the function iText Pdf generated by Html templates, but the practical application, we can not find iText for advanced CSS style parsing, such as the CSS position properties, etc., so we have to introduce new components
If the Chinese do not show or variable, then add in the pom.xml as follows:
<build>
<resources>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
</resource>
</resources>
<!--增加的配置,过滤ttf文件的匹配-->
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-resources-plugin</artifactId>
<version>2.7</version>
<configuration>
<encoding>UTF-8</encoding>
<nonFilteredFileExtensions>
<nonFilteredFileExtension>ttf</nonFilteredFileExtension>
</nonFilteredFileExtensions>
</configuration>
</plugin>
</plugins>
</build>
备注：工具类的方法 PathUtil.getCurrentPath() = "src/main/resources/",(这个对新手有用）
6.Flying Saucer-CSS高级特性支持
Flying Saucer is a pure-Java library for rendering arbitrary well-formed XML (or XHTML) using CSS 2.1 for layout and formatting, output to Swing panels, PDF, and images.
Flying Saucer是基于iText的，支持对CSS高级特性的解析。
添加依赖:
<!-- https://mvnrepository.com/artifact/org.xhtmlrenderer/flying-saucer-pdf -->
<dependency>
<groupId>org.xhtmlrenderer</groupId> <artifactId>flying-saucer-pdf</artifactId> <version>9.1.5</version> </dependency> <!-- https://mvnrepository.com/artifact/org.xhtmlrenderer/flying-saucer-pdf-itext5 --> <dependency> <groupId>org.xhtmlrenderer</groupId> <artifactId>flying-saucer-pdf-itext5</artifactId> <version>9.1.5</version> </dependency>添加模板:template_freemarker_fs.html
<!DOCTYPE html>
<html lang="en"> <head> <meta charset="UTF-8"/> <title>Title</title> <style> body{ font-family:SimHei; } .color{ color: green; } .pos{ position:absolute; left:200px; top:5px; width: 200px; font-size: 10px; } </style> </head> <body> <img src="logo.png" width="600px"/> <div class="color pos"> 你好，${name} </div> </body> </html>测试代码:JavaToPdfHtmlFreeMarker
package com.lujianing.test.flyingsaucer;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.pdf.BaseFont;
import com.lujianing.test.util.PathUtil;
import freemarker.template.Configuration; import freemarker.template.Template; import org.xhtmlrenderer.pdf.ITextFontResolver; import org.xhtmlrenderer.pdf.ITextRenderer; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.StringWriter; import java.io.Writer; import java.util.HashMap; import java.util.Map; /** * Created by lujianing on 2017/5/7. */ public class JavaToPdfHtmlFreeMarker { private static final String DEST = "target/HelloWorld_CN_HTML_FREEMARKER_FS.pdf"; private static final String HTML = "template_freemarker_fs.html"; private static final String FONT = "simhei.ttf"; private static final String LOGO_PATH = "file://"+PathUtil.getCurrentPath()+"/logo.png"; private static Configuration freemarkerCfg = null; static { freemarkerCfg =new Configuration(); //freemarker的模板目录 try { freemarkerCfg.setDirectoryForTemplateLoading(new File(PathUtil.getCurrentPath())); } catch (IOException e) { e.printStackTrace(); } } public static void main(String[] args) throws IOException, DocumentException, com.lowagie.text.DocumentException { Map<String,Object> data = new HashMap(); data.put("name","鲁家宁"); String content = JavaToPdfHtmlFreeMarker.freeMarkerRender(data,HTML); JavaToPdfHtmlFreeMarker.createPdf(content,DEST); } /** * freemarker渲染html */ public static String freeMarkerRender(Map<String, Object> data, String htmlTmp) { Writer out = new StringWriter(); try { // 获取模板,并设置编码方式 Template template = freemarkerCfg.getTemplate(htmlTmp); template.setEncoding("UTF-8"); // 合并数据模型与模板 template.process(data, out); //将合并后的数据和模板写入到流中，这里使用的字符流 out.flush(); return out.toString(); } catch (Exception e) { e.printStackTrace(); } finally { try { out.close(); } catch (IOException ex) { ex.printStackTrace(); } } return null; } public static void createPdf(String content,String dest) throws IOException, DocumentException, com.lowagie.text.DocumentException { ITextRenderer render = new ITextRenderer(); ITextFontResolver fontResolver = render.getFontResolver(); fontResolver.addFont(FONT, BaseFont.IDENTITY_H, BaseFont.NOT_EMBEDDED); // 解析html生成pdf render.setDocumentFromString(content); //解决图片相对路径的问题 render.getSharedContext().setBaseURL(LOGO_PATH); render.layout(); render.createPDF(new FileOutputStream(dest)); } }输出结果:
在某些场景下，html中的静态资源是在本地，我们可以使用render.getSharedContext().setBaseURL()加载文件资源,注意资源URL需要使用文件协议 "file://"。
对于生成的pdf页面大小，可以用css的@page属性设置。
7.PDF转图片
在某些场景中，我们可能只需要返回图片格式的电子凭证，我们可以使用Jpedal组件，把pdf转成图片
添加依赖:
<!-- https://mvnrepository.com/artifact/org.jpedal/jpedal-lgpl -->
<dependency>
<groupId>org.jpedal</groupId> <artifactId>jpedal-lgpl</artifactId> <version>4.74b27</version> </dependency>测试代码:JavaToPdfImgHtmlFreeMarker
package com.lujianing.test.flyingsaucer;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.pdf.BaseFont;
import com.lujianing.test.util.PathUtil;
import freemarker.template.Configuration; import freemarker.template.Template; import org.jpedal.PdfDecoder; import org.jpedal.exception.PdfException; import org.jpedal.fonts.FontMappings; import org.xhtmlrenderer.pdf.ITextFontResolver; import org.xhtmlrenderer.pdf.ITextRenderer; import java.awt.image.BufferedImage; import java.io.ByteArrayOutputStream; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.StringWriter; import java.io.Writer; import java.util.HashMap; import java.util.Map; import javax.imageio.ImageIO; /** * Created by lujianing on 2017/5/7. */ public class JavaToPdfImgHtmlFreeMarker { private static final String DEST = "target/HelloWorld_CN_HTML_FREEMARKER_FS_IMG.png"; private static final String HTML = "template_freemarker_fs.html"; private static final String FONT = "simhei.ttf"; private static final String LOGO_PATH = "file://"+PathUtil.getCurrentPath()+"/logo.png"; private static final String IMG_EXT = "png"; private static Configuration freemarkerCfg = null; static { freemarkerCfg =new Configuration(); //freemarker的模板目录 try { freemarkerCfg.setDirectoryForTemplateLoading(new File(PathUtil.getCurrentPath())); } catch (IOException e) { e.printStackTrace(); } } public static void main(String[] args) throws IOException, DocumentException, com.lowagie.text.DocumentException { Map<String,Object> data = new HashMap(); data.put("name","鲁家宁"); String content = JavaToPdfImgHtmlFreeMarker.freeMarkerRender(data,HTML); ByteArrayOutputStream pdfStream = JavaToPdfImgHtmlFreeMarker.createPdf(content); ByteArrayOutputStream imgSteam = JavaToPdfImgHtmlFreeMarker.pdfToImg(pdfStream.toByteArray(),2,1,IMG_EXT); FileOutputStream fileStream = new FileOutputStream(new File(DEST)); fileStream.write(imgSteam.toByteArray()); fileStream.close(); } /** * freemarker渲染html */ public static String freeMarkerRender(Map<String, Object> data, String htmlTmp) { Writer out = new StringWriter(); try { // 获取模板,并设置编码方式 Template template = freemarkerCfg.getTemplate(htmlTmp); template.setEncoding("UTF-8"); // 合并数据模型与模板 template.process(data, out); //将合并后的数据和模板写入到流中，这里使用的字符流 out.flush(); return out.toString(); } catch (Exception e) { e.printStackTrace(); } finally { try { out.close(); } catch (IOException ex) { ex.printStackTrace(); } } return null; } /** * 根据模板生成pdf文件流 */ public static ByteArrayOutputStream createPdf(String content) { ByteArrayOutputStream outStream = new ByteArrayOutputStream(); ITextRenderer render = new ITextRenderer(); ITextFontResolver fontResolver = render.getFontResolver(); try { fontResolver.addFont(FONT, BaseFont.IDENTITY_H, BaseFont.NOT_EMBEDDED); } catch (com.lowagie.text.DocumentException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } // 解析html生成pdf render.setDocumentFromString(content); //解决图片相对路径的问题 render.getSharedContext().setBaseURL(LOGO_PATH); render.layout(); try { render.createPDF(outStream); return outStream; } catch (com.lowagie.text.DocumentException e) { e.printStackTrace(); } finally { try { outStream.close(); } catch (IOException e) { e.printStackTrace(); } } return null; } /** * 根据pdf二进制文件 生成图片文件 * * @param bytes pdf二进制 * @param scaling 清晰度 * @param pageNum 页数 */ public static ByteArrayOutputStream pdfToImg(byte[] bytes, float scaling, int pageNum,String formatName) { //推荐的方法打开PdfDecoder PdfDecoder pdfDecoder = new PdfDecoder(true); FontMappings.setFontReplacements(); //修改图片的清晰度 pdfDecoder.scaling = scaling; ByteArrayOutputStream out = new ByteArrayOutputStream(); try { //打开pdf文件，生成PdfDecoder对象 pdfDecoder.openPdfArray(bytes); //bytes is byte[] array with PDF //获取第pageNum页的pdf BufferedImage img = pdfDecoder.getPageAsImage(pageNum); ImageIO.write(img, formatName, out); } catch (PdfException e) { e.printStackTrace(); } catch (IOException e){ e.printStackTrace(); } return out; } }输出结果：
Jpedal支持将指定页Pdf生成图片，pdfDecoder.scaling设置图片的分辨率(不同分辨率下文件大小不同) ，支持多种图片格式，具体更多可自行研究
8.总结
对于电子凭证的技术方案，总结如下:
1.html模板+model数据，通过freemarker进行渲染，便于维护和修改
2.渲染后的html流，可通过Flying Saucer组件生成pdf文件流，或者生成pdf后再转成jpg文件流
3.在Web项目中，对应的文件流，可以通过ContentType设置，在线查看/下载，不需通过附件服务
9.纯前端解决方案
还有一种解决方案是使用PhantomJS
git地址: https://github.com/ariya/phantomjs
PhantomJS 是一个基于 WebKit 的服务器端 JavaScript API。它全面支持web而不需浏览器支持，其快速，原生支持各种Web标准： DOM 处理, CSS 选择器, JSON, Canvas, 和 SVG。 PhantomJS 可以用于 页面自动化 ， 网络监测 ， 网页截屏 ，以及 无界面测试 等。
具体方法可自行查询。