java html模板转图片、动态绑定数据

动态填充html中数据，生成流对象, 在转成图片

此过程中简单样式的html效果还可以，但是遇到复杂的css兼容性不太好

以下示例使用gradle引入freemarker、xhtmlrenderer

dependencies {
    implementation 'org.freemarker:freemarker-gae'
    implementation 'org.xhtmlrenderer:core-renderer'
}

Java生成对象流

package com.xxxxx.utils;

import freemarker.template.Configuration;
import freemarker.template.Template;
import freemarker.template.TemplateException;
import freemarker.template.TemplateExceptionHandler;
import org.springframework.util.ResourceUtils;
import org.w3c.dom.Document;
import javax.imageio.ImageIO;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import java.awt.image.BufferedImage;
import java.io.*;
import java.util.Locale;
import java.util.Map;
import java.io.File;
import java.io.IOException;
import org.xhtmlrenderer.swing.Java2DRenderer;


public class HtmlToImgUtils {
    
    private static String IMG_DEFAULT_PNG = "png";

    
    private static int DEFAULT_WIDTH = 1100;
    
    private static int DEFAULT_HEIGHT = 1100;

    
    public static ByteArrayOutputStream getImageStream(String networkAddress, String fileName, Map map) throws Exception {
        String html = getNetworkDirectoryTemplate(networkAddress, fileName, map);
        return htmlToStream(html, map);
    }

    
    private static String getNetworkDirectoryTemplate(String networkAddress, String fileName, Map map) throws IOException, TemplateException {
        Configuration cfg = new Configuration(Configuration.VERSION_2_3_28);
        //读取网络文件路径
        RemoteTemplateLoader templateLoader = new RemoteTemplateLoader(networkAddress);
        cfg.setTemplateLoader(templateLoader);
        cfg.setTemplateExceptionHandler(TemplateExceptionHandler.RETHROW_HANDLER);
        cfg.setLogTemplateExceptions(false);
        cfg.setEncoding(Locale.CHINA, "UTF-8");
        //路径下读取文件
        Template temp = cfg.getTemplate(fileName, Locale.CHINA, "UTF-8");
        StringWriter stringWriter = new StringWriter();
        temp.process(map, stringWriter);
        stringWriter.flush();
        stringWriter.close();
        return stringWriter.getBuffer().toString();
    }


    
    public static ByteArrayOutputStream getImageStreamLocal(String localFileName, Map map) throws Exception {
        String html = getTemplate(localFileName, map);
        return htmlToStream(html, map);
    }


    
    private static String getTemplate(String localFileName, Map map) throws IOException, TemplateException {
        Configuration cfg = new Configuration(Configuration.VERSION_2_3_25);
        //读取文件路径，自行配置本地模板存放地址，TODO
        File file = ResourceUtils.getFile("classpath:templates");
        cfg.setDirectoryForTemplateLoading(file);
        cfg.setTemplateExceptionHandler(TemplateExceptionHandler.RETHROW_HANDLER);
        cfg.setLogTemplateExceptions(false);
        //路径下读取文件
        Template temp = cfg.getTemplate(localFileName);
        StringWriter stringWriter = new StringWriter();
        temp.process(map, stringWriter);
        stringWriter.flush();
        stringWriter.close();
        return stringWriter.getBuffer().toString();
    }


    
    private static ByteArrayOutputStream htmlToStream(String html, Map map) throws Exception {
        String extension = map.get("extension") != null ? String.valueOf(map.get("extension")) : IMG_DEFAULT_PNG;
        int width = map.get("width") != null ? Integer.parseInt(String.valueOf(map.get("width"))) : DEFAULT_WIDTH;
        int height = map.get("height") != null ? Integer.parseInt(String.valueOf(map.get("height"))) : DEFAULT_HEIGHT;

        byte[] bytes = html.getBytes();
        ByteArrayInputStream bin = new ByteArrayInputStream(bytes);
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        Document document = builder.parse(bin);
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        Java2DRenderer renderer = new Java2DRenderer(document, width, height);
        BufferedImage img = null;
        try {
            //原图
            img = renderer.getImage();
            if (img == null) {
                throw new Exception("无法加载原始图片");
            }
            //这里省略对图像进行处理
            ImageIO.write(img, extension, outputStream);
        } catch (IOException ex) {
            throw new Exception(ex.getMessage());
        } finally {
            if (img != null) {
                img.getGraphics().dispose();
            }
        }

        return outputStream;
    }
}

ftl文件代码为html, 扩展名是ftl

!DOCTYPE html>


    
    
    



    

        

            
单据编号：
            
${orderNo}
            
销售日期：
            
${createTime}
        
    
    
<#--        ftl支持循环语法，循环一个list， 仅仅展示语法, 已被注释，  -->
<#--        <#list productList as product>-->
<#--            -->
<#--                
${product.supplyProductNo}
-->
<#--                
${product.productName}
-->
<#--                ${product.productNumber}-->
<#--                ${product.productUnitPrice}-->
<#--                ${product.productActualAmount}-->
<#--            -->
<#--        -->

//绑定动态数据
Map map = new HashMap<>();
map.put("orderNo", '164165313123');
map.put("createTime", "2022-02-02");

//阿里云的oss模板路径
ByteArrayOutputStream oStream = HtmlToImgUtils.getImageStream(
												"https://oss-cn-xxxx.aliyuncs.com/template/", 
												"index.ftl",
												 map);

//服务器本地模板路径
ByteArrayOutputStream oStream1 = HtmlToImgUtils.getImageStreamLocal(
												"index.ftl",
												 map);
//ByteArrayOutputStre生成图片的过程自行补全