activiti5显示流程图

从数据库中以输入流的方式读取出图片数据，然后在jsp页面中读取输入流，以图片的格式显示出图片。  

InputStream中实际上就是流程图，然后就是以怎样的相应格式显示InputStream中的内容。

service层

  /**

       * 读取带跟踪的图片

       */

    public InputStream readResource(String executionId){

        InputStream imageStream = null;

        ProcessInstance processInstance = runtimeService.createProcessInstanceQuery().processInstanceId(executionId).singleResult();

        BpmnModel bpmnModel = repositoryService.getBpmnModel(processInstance.getProcessDefinitionId());

        List<String> activeActivityIds = runtimeService.getActiveActivityIds(executionId);

        ProcessEngineImpl defaultProcessEngine = (ProcessEngineImpl) ProcessEngines.getDefaultProcessEngine();

        

        Context.setProcessEngineConfiguration(defaultProcessEngine.getProcessEngineConfiguration());

        Context.setProcessEngineConfiguration(((ProcessEngineImpl) processEngine).getProcessEngineConfiguration());

        

        imageStream = ProcessDiagramGenerator.generateDiagram(bpmnModel, "png", activeActivityIds);

        

        return imageStream;
    }

struts2 action中

    //从数据库中得到运行流程图，带标红

    public String readResource(){

        HttpServletResponse response = ServletActionContext.getResponse();

        HttpServletRequest request = ServletActionContext.getRequest();

        ActivitiController activitiController = new ActivitiController();

        InputStream imageStream = activitiController.readResource(processInstanceId);

        request.setAttribute("inputStream", imageStream);

        

        /*byte[] b = new byte[1024];

        int len = -1;

        try {

            while ((len = imageStream.read(b, 0, 1024)) != -1) {

                response.getOutputStream().write(b, 0, len);

            }

        } catch (IOException e) {

            e.printStackTrace();

        }*/

        

        return "showImage";

    }

jsp页面    需要设置response的相应格式

    <%

        response.setContentType("image/png;charset=UTF-8");

        response.setCharacterEncoding("UTF-8");

        InputStream is = (InputStream)request.getAttribute("inputStream");

        byte[] b = new byte[1024];

        int len = -1;

        while((len = is.read(b, 0, 1024)) != -1) {

            response.getOutputStream().write(b, 0, len);

            // 防止异常：getOutputStream() has already been called for this response

            out.clear();

            out = pageContext.pushBody();

        }    

    %>

或者

struts2 action中

    //从数据库中得到运行流程图，带标红

    public String readResource(){

        HttpServletResponse response = ServletActionContext.getResponse();

        HttpServletRequest request = ServletActionContext.getRequest();

        ActivitiController activitiController = new ActivitiController();

        InputStream imageStream = activitiController.readResource(processInstanceId);

        request.setAttribute("inputStream", imageStream);

        

        byte[] b = new byte[1024];

        int len = -1;

        try {

            while ((len = imageStream.read(b, 0, 1024)) != -1) {

                response.getOutputStream().write(b, 0, len);

            }

        } catch (IOException e) {

            e.printStackTrace();

        }

        

        return null;

    }

在jsp页面中用

<img src="<%=basePath%>oa/leaveAction!readResource"/>   以图片的方式自动加载