一个AJAX+Spring MVC程序的基本原理

程序功能描述：在页面上点击一个“Disable Account”按钮，后台实现Disable某个账号，程序原理如下：

1. 首先在页面上点击按钮，该按钮的ID是“disableAccountBtn”，找出页面加载的JS文件，在文件中搜索出该ID，发现如下代码：

   $('#disableAccountBtn').click(function() {
   $('#promptWinYes').unbind('click').click(function() {
   $('#promptWin').dialog('close');
   $.getJSON(DISABLE_USER_ACTION, {
   uid : clientId
   }, function(data) {
   switchButtonVisible(false);
   showAlertWin('Warning', DISABLE_USER_CALLBACK_MSG);
   });
   });
   showPromptWin('Warning', DISABLE_USER_MSG);
   }); 

    其中$.getJSON来调用并获取远程的JSON字符串，将其转换为JSON对象，如果成功，则执行回调函数,再从JS中查找DISABLE_USER_ACTION="../disableUser.action. 可见这个调用最终执行了
   ../disableUser.action?uid=userID这个service
2. 查找后台JAVA代码，在UserManagementController.java中找到如下方法：

   @RequestMapping("/disableUser.action")
   	public ModelAndView disableUser(HttpServletRequest request)
   			throws Exception {
   		return WorkflowController.disableClient(request, clientAction);
   	}

    此处用的是Spring MVC的框架，这个方法用到了clientAction
   
3. 再进入WorkflowController.disableClient(request, clientAction)

    public static ModelAndView disableClient(HttpServletRequest httpReq, ClientAction clientAction) {
           String clientId = httpReq.getParameter("uid");
           UserBean sales = resolveSales(httpReq);
   
           String methodId = "{" + sales.getId() + "," + clientId + "," + System.currentTimeMillis() + "}";
           logger.info("/disableUser.action BEGIN " + methodId);
   
           boolean success = true;
           String errorMsg = null;
           try {
               clientAction.disableClient(clientId, sales);
           } catch (Throwable e) {
               logger.error("Failed to disable user " + methodId, e);
               success = false;
               errorMsg = "Server Internal Error. Please contact the system Admin.";
           } finally {
               logger.info("/disableUser.action END " + methodId);
           }
   
           ModelMap model = new ModelMap();
           model.addAttribute("success", success);
           model.addAttribute("errorMsg", errorMsg);
           return new ModelAndView("results", model);
       }

    可见，这个service执行成功后，返回的字符串是

   {"errorMsg":null,"success":true}

4. 进入clientAction.disableClient(clientId, sales)方法，ClientAction里面有很多方法：

    /**
        * Action to disable an existing client.
        * 
        * @param clientId
        * @param currentUser
        * @throws Exception
        */
       public void disableClient(String clientId, UserBean currentUser) throws Exception {
       	umUserService.createESFDataIfMissing(clientId);
           UserProfile oldUser = umUserService.getUserProfile(clientId);
           disableClient(currentUser, oldUser);
       }

    
5. 再进入dsiableClient:

    void disableClient(UserBean salesUserBean, UserProfile clientUserProfile) throws Exception {
           if (salesUserBean == null || clientUserProfile == null) {
               return;
           }
           String clientId = clientUserProfile.getUid();
           String clientName = clientUserProfile.getDisplayName();
           UserRequestEntity userEntity = new UserRequestEntity();
           userEntity.setTitle(UMTConstants.USER_PROFILE_TITLE + "(Disable)");
           userEntity.setClientId(clientId);
           userEntity.setClientName(clientName);
           userEntity.setSalesId(salesUserBean.getId());
           userEntity.setSalesName(salesUserBean.getName());
   
           //restore old user profile
           try {
               userEntity.setProfile(JsonUtil.write(clientUserProfile));
           } catch (Exception e) {
               logger.error("Failed to encode user profile into JSON.", e);
           }
   
           umWorkflow.startDisableClientWorkflow(userEntity, UMTConstants.WF_DISABLE_CLIENT);
       } 

6. 最后调用通用的startDisableClientWorkflow（）方法：

    /**
        * Start the workflow to disable an existing client.
        * 
        * @param userEntity the user profile provided by front-end, cannot be null
        */
       public void startDisableClientWorkflow(UserRequestEntity userEntity, String workflowName) throws Exception {
           //1) save records into request tables
           UserRequestEntityHelper.validatePV(userEntity);
           UMRequestEntity umEntity = requestTracker.save(userEntity);
           Long requestId = umEntity.getId();
           logger.info("Saved request entity of [disable] for {" + userEntity.getClientId() + "} as " + requestId);
   
           //2) update request status
           umEntity.setStatus(UMRequestEntity.Status.ESF_DISABLE);
           startWorkflow(requestId, workflowName, umEntity);
       }

    startWorkflow():

    /**
        * Start workflow for request.
        * 
        * @param requestId
        * @param workflowName
        * @param umEntity
        * @throws Exception
        */
       public void startWorkflow(Long requestId, String workflowName, UMRequestEntity umEntity) throws Exception {
           logger.info("Start workflow " + workflowName + " for request [" + requestId + "]");
   
           //1) get workflow and start the process instance
           UMWorkflowBean workflowBean = workflowRepository.findUMWorkflowByName(workflowName);
           String processId = workflowService.startProcessInstance(workflowBean.getProcessName(), new HashMap<String, String>());
   
           //2) update request status
           if (umEntity == null) {
               umEntity = new UMRequestEntity();
               umEntity.setStatus(UserRequestEntity.Status.PROCESSING);
               umEntity.setStatusFlag(0);
           }
           umEntity.setId(requestId);
           umEntity.setWorkflowId(workflowBean.getWorkflowId());
           umEntity.setProcessId(processId);
           requestTracker.update(umEntity);
           logger.info("Started workflow for request [" + requestId + "]");
   
           //3) transit to first state
           Set<String> nextStates = workflowService.findActiveStates(processId);
           StateHandler nextStateHandler = null;
           for (String nextState : nextStates) {
               nextStateHandler = handlerRepository.getByState(nextState);
               if (nextStateHandler != null) {
                   break;
               }
           }
           if (nextStateHandler != null) {
               nextStateHandler.execute(requestId);   
           }
       }
   }

7.  找到WorkFlowService的实现类对应的方法：

    /**
        * Start the process instance.
        * 
        */
       public String startProcessInstance(String processKey, Map<String, String> variables) {
           ProcessInstance processInstance = executionService.startProcessInstanceByKey(processKey, variables);
           return processInstance.getId();
       }

    ExecutionService这个类属于JBPM，全称是Java Business Process Management，是一种基于J2EE的轻量级工作流管理系统。

总结：这类AJAX+Spring MVC的程序基本原理就是前台JS代码去调用后台的Service.测试的时候打开Fidder或者Firebug就能捕捉到具体的service已经传递的参数

接下去是真证的Disable逻辑：

1. 在ESFServiceImpl里有一个disableUser（）方法：

   public void disableUser(String operator, String userId) throws Exception {
   		//		Map<String, String> userESFAttrMap = queryUserESFInfo(userId);
   		//		if (userESFAttrMap == null) {
   		//			throw new Exception("Disable user error. Can not find user: "
   		//					+ userId);
   		//		}
   		//		if (ESFConstans.STATUS_ENABLED.equals(userESFAttrMap
   		//				.get(ESFConstans.CLIENT_USERS_ATTR.STATUS))) {
   		//			changeUserStatus(operator, userId);
   		//		}
   		Connection con = null;
   		CallableStatement st = null;
   		ResultSet rs = null;
   		try {
   			con = getConnection();
   			st = con.prepareCall(ESFConstans.CALL_DISABLE_USER);
   			st.setString(1, userId);
   			st.setString(2, operator);
   			st.execute();
   		} catch (SQLException e) {
   			throw e;
   		} catch (Exception e) {
   			throw e;
   		} finally {
   			closeAllDBResources(rs, st, con);
   		}
   	}

    其中使用CallableStatement调用了存储过程ESFConstans.CALL_DISABLE_USER：

   public static final String CALL_DISABLE_USER = "call "
   		+ schema
   		+ "cdc_rules_gmo_serve."
   		+ profix
   		+ "set_status_v2(?,0,?)";