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

一、引入依赖包

以下示例使用gradle引入freemarker、xhtmlrenderer

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

二、引入依赖包

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;

/**
 * @author
 * @date
 */
public class HtmlToImgUtils {
    /***
     * 默认画布宽度 1100px
     */
    private static String IMG_DEFAULT_PNG = "png";

    /***
     * 默认画布宽度 1100px
     */
    private static int DEFAULT_WIDTH = 1100;
    /***
     * 默认画布高度 1100px
     */
    private static int DEFAULT_HEIGHT = 1100;

    /**
     * 得到图片流   可用于读取oss模板
     *
     * @param networkAddress  网络模板路径 https://xxxxxx.com/template/
     * @param fileName    模板名称  index.html
     * @param map              map.extension  设置扩展名,可空, 默认值:png,   jpg、png等
     *                         map.width  设置画布宽度,可空, 默认值:1100,   单位px
     *                         map.height  设置画布高度,可空, 默认值:1000,  单位px
     * @return ByteArrayOutputStream
     */
    public static ByteArrayOutputStream getImageStream(String networkAddress, String fileName, Map<String, Object> map) throws Exception {
        String html = getNetworkDirectoryTemplate(networkAddress, fileName, map);
        return htmlToStream(html, map);
    }

    /**
     * 读取模板
     *
     * @param networkAddress 模板目录 https://xxxxxx.com/template/index.html
     * @param fileName     模板名称 index.html
     * @param map
     * @return
     */
    private static String getNetworkDirectoryTemplate(String networkAddress, String fileName, Map<String, Object> 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();
    }


    /**
     * 得到图片流  可用于读取本地模板
     *
     * @param localFileName 本地模板名称
     * @param map
     * @return ByteArrayOutputStream
     */
    public static ByteArrayOutputStream getImageStreamLocal(String localFileName, Map<String, Object> map) throws Exception {
        String html = getTemplate(localFileName, map);
        return htmlToStream(html, map);
    }


    /**
     * 读取模板
     *
     * @param localFileName 模板名称
     * @param map
     * @return String
     */
    private static String getTemplate(String localFileName, Map<String, Object> 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();
    }


    /**
     * html模板转图片流
     *
     * @param html html模板
     * @return ByteArrayOutputStream
     */
    private static ByteArrayOutputStream htmlToStream(String html, Map<String, Object> 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;
    }
}

三、编写ftl文件

ftl文件代码为html, 扩展名是ftl

!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head lang="en">
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">meta>
    <title>testtitle>
    <style>
        body {
            font-family:"宋体";
        }

        .container {
            position: relative;
            box-sizing: border-box;
            -moz-box-sizing: border-box; /* Firefox */
            -webkit-box-sizing: border-box; /* Safari */
            width: 1000px;
            padding: 50px 50px 50px 50px;
        }

        .table_box {
            width: 100%;
        }

        td {
            min-height: 44px;
            padding-left: 8px;
        }

        .col_15 {
            width: 15%;
        }

        .col_40 {
            width: 40%;
        }
    style>
head>
<body>
<div class="container">
    <table class="table_box" border="1" cellspacing="0" frame="box" rules="all">
        <tr>
            <td class="col_15">单据编号：td>
            <td class="col_40">${orderNo}td>
            <td class="col_15">销售日期：td>
            <td class="col_40">${createTime}td>
        tr>
    table>
    
<#--        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>-->
<#--            >-->
<#--                 class="col_15"><div>${product.supplyProductNo}div>td>-->
<#--                 class="col_40"><div>${product.productName}div>td>-->
<#--                 class="col_15">${product.productNumber}td>-->
<#--                 class="col_15">${product.productUnitPrice}td>-->
<#--                 class="col_15">${product.productActualAmount}td>-->
<#--            tr>-->
<#--        #list>-->

div>
body>
html>

四、调用

//绑定动态数据
Map<String, Object> 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