Feign实现微服务间调用返回stream

叁歲伎倆 2022-01-22 07:55 1001阅读 0赞

今天来讲述一下fegin的调用返回stream，得到stream我们可以下载，写入到页面展示图片等；  
我们就开始讲述一下：

*  服务提供者流接口

@RequestMapping(value = "feginProcessDiagram", method = RequestMethod.GET, consumes = MediaType.APPLICATION_JSON_UTF8_VALUE)
    public void genFeginProcessDiagram(HttpServletResponse httpServletResponse, String processId) throws Exception {
        ProcessInstance pi = runtimeService.createProcessInstanceQuery().processInstanceId(processId).singleResult();
        //流程走完的不显示图
        if (pi == null) {
            return;
        }
        Task task = taskService.createTaskQuery().processInstanceId(pi.getId()).singleResult();
        //使用流程实例ID，查询正在执行的执行对象表，返回流程实例对象
        String InstanceId = task.getProcessInstanceId();
        List < Execution > executions = runtimeService.createExecutionQuery().processInstanceId(InstanceId).list();
        //得到正在执行的Activity的Id
        List < String > activityIds = new ArrayList < > ();
        List < String > flows = new ArrayList < > ();
        for (Execution exe: executions) {
            List < String > ids = runtimeService.getActiveActivityIds(exe.getId());
            activityIds.addAll(ids);
        }
        //获取流程图
        BpmnModel bpmnModel = repositoryService.getBpmnModel(pi.getProcessDefinitionId());
        ProcessEngineConfiguration engconf = processEngine.getProcessEngineConfiguration();
        ProcessDiagramGenerator diagramGenerator = engconf.getProcessDiagramGenerator();
        InputStream in = diagramGenerator.generateDiagram(bpmnModel, "png", activityIds, flows, engconf.getActivityFontName(),
            engconf.getLabelFontName(), engconf.getAnnotationFontName(), engconf.getClassLoader(), 1.0, true);
        OutputStream out = null;
        byte[] buf = new byte[1024];
        int legth = 0;
        try {
            out = httpServletResponse.getOutputStream();
            while ((legth = in .read(buf)) != -1) {
                out.write(buf, 0, legth);
            }
        } finally {
            if ( in != null) {
                in .close();
            }
            if (out != null) {
                out.close();
            }
        }
    }

*  服务提供者远程调用接口

@RequestMapping(value = "/expense/feginProcessDiagram",method = RequestMethod.GET,consumes = MediaType.APPLICATION_JSON_UTF8_VALUE)
    Response genFeginProcessDiagram(@RequestParam("httpServletResponse") HttpServletResponse httpServletResponse, @RequestParam("processId") String processId) throws Exception;

用feign.Response来接收

*  服务提供者下载文件接口

@RequestMapping(value = "ribbonProcessDiagram/{processId}")
    public void genProcessDiagram1(HttpServletResponse httpServletResponse, @PathVariable String processId) throws Exception {
        ResponseEntity<Resource> entity = restTemplate.postForEntity("http://microservice-flowable/expense/ribbonProcessDiagram/{processId}", processId, Resource.class,processId);
        InputStream in = entity.getBody().getInputStream();
        System.out.println(in);
    
        OutputStream out = null;
        byte[] buf = new byte[1024];
        int legth = 0;
        try {
          out = httpServletResponse.getOutputStream();
          while ((legth = in.read(buf)) != -1) {
            out.write(buf, 0, legth);
          }
        } finally {
          if (in != null) {
            in.close();
          }
          if (out != null) {
            out.close();
          }
        }
    }

只要我们拿到InputStream然后我们就可以操作了，下载，写入直接展示图片！

参考：

[https://blog.csdn.net/aaronsimon/article/details/82710979][https_blog.csdn.net_aaronsimon_article_details_82710979]

[RestTemplate响应中获取输入流InputStream][RestTemplate_InputStream]

[https_blog.csdn.net_aaronsimon_article_details_82710979]: https://blog.csdn.net/aaronsimon/article/details/82710979
[RestTemplate_InputStream]: https://blog.csdn.net/ron_2016/article/details/82884183