activiti7 导出bpmn文件

最近在学习springboot+activiti7整合，想做一个导出bpmn文件的功能，查了相关资料，最后没有实现。最后查看了一下代码 找到了方法 如下所示

@GetMapping("export")
@Transactional
public void export(@RequestParam("definitionId") String processInstanceId, HttpServletResponse response) {
    BufferedOutputStream bos = null;
    try {

        try {
            RepositoryService repositoryService = ProcessEngines.getDefaultProcessEngine().getRepositoryService();
            //
            ProcessDefinition processDefinition = repositoryService.createProcessDefinitionQuery().processDefinitionId(processInstanceId).singleResult();
            InputStream inputStream = repositoryService
                    .getProcessModel(processInstanceId);
            ByteArrayOutputStream swapStream = new ByteArrayOutputStream();
            byte[] bpmnBytes = new byte[1024]; //buff用于存放循环读取的临时数据
            int rc = 0;
            while ((rc = inputStream.read(bpmnBytes, 0, 100)) > 0) {
                swapStream.write(bpmnBytes, 0, rc);
            }
            byte[] in_b = swapStream.toByteArray(); //in_b为转换之后的结果
            // 封装输出流
            bos = new BufferedOutputStream(response.getOutputStream());
            bos.write(in_b);// 写入流

            String filename = processDefinition.getName() + ".bpmn";
            response.setContentType("application/x-msdownload;");
            response.setHeader("Content-Disposition",
                    "attachment; filename=" + filename);
            response.flushBuffer();

        } finally {
            bos.flush();
            bos.close();
        }

    } catch (Exception e) {
        System.out.println("导出文件失败");
        e.printStackTrace();
    }
}
其中

InputStream inputStream = repositoryService
                    .getProcessModel(processInstanceId); 可以获取bpmn文件流 直接操作导出即可