一、实现流程：通过freemarker模板引擎将数据动态添加到模板中，然后将已添加动态数据的模板代码通过xhtmlrenderer转换成图片。
二、依赖jar:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-freemarker</artifactId>
</dependency>
<dependency>
<groupId>org.xhtmlrenderer</groupId>
<artifactId>core-renderer</artifactId>
<version>R8</version>
</dependency>
注意xhtmlrenderer中央仓库为：
<repository>
<id>mvnrepository</id>
<name>mvnrepository</name>
<url>https://mvnrepository.com</url>
</repository>
三、模板引擎配置：
spring:
freemarker:
cache: false
# 字符集
charset: UTF-8
# 检查模板位置
check-template-location: true
# 模板内容类型
content-type: text/html
expose-request-attributes: true
expose-session-attributes: true
request-context-attribute: request
# 模板位置
template-loader-path: classpath:/templates
模板地址对应的地址为：
模板代码 index.ftl
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8"/>
<title>海报</title>
</head>
<body style=" 500px; height: 800px;margin: 0;padding: 0;">
<img src="${img}" alt="" />
<span>${msg}</span>
</body>
</html>
注意：这里全部采用行内样式，却不能有js否则图片会展示出代码
四、生成图片代码
public class FreemarkerUtils {
private static String getTemplate(String template, Map<String,Object> map) throws IOException,TemplateException {
Configuration cfg = new Configuration(Configuration.VERSION_2_3_25);
String templatePath = FreemarkerUtils.class.getResource("/").getPath()+"/templates";
cfg.setDirectoryForTemplateLoading(new File(templatePath));
cfg.setDefaultEncoding("UTF-8");
cfg.setTemplateExceptionHandler(TemplateExceptionHandler.RETHROW_HANDLER);
cfg.setLogTemplateExceptions(false);
Template temp = cfg.getTemplate(template);
StringWriter stringWriter = new StringWriter();
temp.process(map, stringWriter);
stringWriter.flush();
stringWriter.close();
String resutl = stringWriter.getBuffer().toString();
return resutl;
}
public static void turnImage(String template, Map<String,Object> map, HttpServletResponse response) throws Exception {
String html = getTemplate(template, map);
byte[] bytes=html.getBytes();
ByteArrayInputStream bin=new ByteArrayInputStream(bytes);
DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
DocumentBuilder builder=factory.newDocumentBuilder();
Document document=builder.parse(bin);
Java2DRenderer renderer = new Java2DRenderer(document,600,800);
BufferedImage img = renderer.getImage();
response.setContentType("image/jpeg");
response.setDateHeader("expries", -1);
response.setHeader("Cache-Control", "no-cache");
response.setHeader("Pragma", "no-cache");
ImageIO.write(img, "jpg", response.getOutputStream());
}
}
五、测试类
@RequestMapping(value = "/test", method = {RequestMethod.GET})
public void test(HttpServletResponse response) {
try {
Map<String,Object> map=new HashMap<>();
map.put("msg","html--生成图片测试");
map.put("img","https://upload-images.jianshu.io/upload_images/912344-3054132dd6939004.png?imageMogr2/auto-orient/strip|imageView2/1/w/300/h/240");
FreemarkerUtils.turnImage("index.ftl",map,response);
} catch (Exception e) {
log.error("异常", e.getMessage());
}
}
六、效果
补充使用感受:
-
图片不能引用本地图片,
/images/a.png这种形式无法加载,必须是http://xxx/images/a.png形式才行 -
打成jar包,放在linux服务器上,获取不到jar包里面的模板. 线上部署的话,最好通过配置指定模板路径
-
如果需要导出到文件,可以使用下面代码
方式1:
ImageIO.write(img, "jpg", file);
方式2:
FSImageWriter imageWriter = new FSImageWriter();
imageWriter.setWriteCompressionQuality(1.0f);//设置压缩率
imageWriter.write(img, file);