SpringMVC 04(JSON和全局异常处理)
目录
一，SpringMVC对JSON的支持
二，SpringMVC 的全局异常处理
一，SpringMVC对JSON的支持
pom.xml依赖
com.fasterxml.jackson.core
jackson-databind
2.9.3
com.fasterxml.jackson.core
jackson-core
2.9.3
com.fasterxml.jackson.core
jackson-annotations
2.9.3
Springmvc.xml配置
text/html;charset=UTF-8
text/json;charset=UTF-8
application/json;charset=UTF-8
后台代码：
package com.ruojuan.ssm.web;
import com.ruojuan.ssm.Exception.GlobalException;
import com.ruojuan.ssm.biz.ClazzBiz;
import com.ruojuan.ssm.model.Clazz;
import com.ruojuan.ssm.util.PageBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import javax.servlet.http.HttpServletRequest;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* @author ruojuan
* @site 123456999
* @company 玉渊工作室
* @create 2022-08-22 16:25
*/
@ResponseBody
@Controller
@RequestMapping("/clz/json")
public class JsonController {
@Autowired
private ClazzBiz clazzBiz;
/**
* 返回List
* @param req
* @param clazz
* @return
*/
@RequestMapping("/list")
public List list(HttpServletRequest req, Clazz clazz){
PageBean pageBean = new PageBean();
pageBean.setRequest(req);
if(true) {
throw new RuntimeException("查询班级信息异常，异常存在于JsonController.list方法");
}
List lst = this.clazzBiz.listPager(clazz, pageBean);
return lst;
}
/**
* 返回T
* @param req
* @param clazz
* @return
*/
/*@RequestMapping("/load")
public Clazz load(HttpServletRequest req, Clazz clazz){
PageBean pageBean = new PageBean();
pageBean.setRequest(req);
if(true){
throw new GlobalException("系统繁忙，请参考E007;");
}
return this.clazzBiz.listPager(clazz,pageBean).get(0);
}*/
@RequestMapping("/load")
public Clazz load(HttpServletRequest req, Clazz clazz){
if(clazz.getCid() != null){
List lst = this.clazzBiz.listPager(clazz, null);
if (true)
throw new GlobalException("错误出现在 JsonController.load...");
return lst.get(0);
}
return null;
}
/**
* 返回List servic层 ：
public ListMapper.xml
测试：
<%--
Created by IntelliJ IDEA.
User: Administrator
Date: 2022/8/22
Time: 16:46
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
测试json数据返回
返回list<T>对象
返回list<Map>对象
返回T对象
返回Map对象
返回混合对象
效果：
二，SpringMVC 的全局异常处理
1.为什么要全局异常处理
我们知道，系统中异常包括：编译时异常和运行时异常RuntimeException，前者通过捕获异常从而获取异常信息，后者主要通过规范代码开发、测试通过手段减少运行时异常的发生。在开发中，不管是dao层、service层还是controller层，都有可能抛出异常，在springmvc中，能将所有类型的异常处理从各处理过程解耦出来，既保证了相关处理过程的功能较单一，也实现了异常信息的统一处理和维护。
2.异常处理思路
系统的dao、service、controller出现异常都通过throws Exception向上抛出，最后由springmvc前端控制器交由异常处理器进行异常处理。springmvc提供全局异常处理器（一个系统只有一个异常处理器）进行统一异常处理。
3.SpringMVC异常分类
1）使用Spring MVC提供的简单异常处理器SimpleMappingExceptionResolver；
2）实现Spring的异常处理接口HandlerExceptionResolver自定义自己的异常处理器；
3）使用@ControllerAdvice + @ExceptionHandler
JsonController ：
/**
* 返回List
* @param req
* @param clazz
* @return
*/
@ResponseBody
@RequestMapping("/list")
public List list(HttpServletRequest req, Clazz clazz){
PageBean pageBean = new PageBean();
pageBean.setRequest(req);
if(true) {
throw new RuntimeException("查询班级信息异常，异常存在于JsonController.list方法");
}
List lst = this.clazzBiz.listPager(clazz, pageBean);
return lst;
}
/**
* 返回List Bizimpl:
@Override
public List效果：
SpringMVC自带的简单异常处理器
springmvc-servlet.xml
error
error.jsp
${ex}
4. 通过HandlerExceptionResovler接口实现全局异常
先将上面SpringMVC中关于异常处理的配置取消掉
全局异常GlobalException.java：
package com.ruojuan.ssm.Exception;
/**
* @author ruojuan
* @site 123456999
* @company 玉渊工作室
* @create 2022-08-22 17:16
*/
public class GlobalException extends RuntimeException{
public GlobalException() {
}
public GlobalException(String message) {
super(message);
}
public GlobalException(String message, Throwable cause) {
super(message, cause);
}
public GlobalException(Throwable cause) {
super(cause);
}
public GlobalException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
super(message, cause, enableSuppression, writableStackTrace);
}
}
异常处理器 GlobalHandlerExceptionResovler
package com.ruojuan.ssm.Exception;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* @author ruojuan
* @site 123456999
* @company 玉渊工作室
* @create 2022-08-22 17:52
*
* 处理全局异常的解析器
*/
@Component
public class GlobalHandlerExceptionResovler implements HandlerExceptionResolver {
/**
*
* @param httpServletRequest
* @param httpServletResponse
* @param o 目标对象
* @param e
* @return
*/
@Override
public ModelAndView resolveException(HttpServletRequest httpServletRequest,
HttpServletResponse httpServletResponse,
Object o, Exception e) {
ModelAndView mv = new ModelAndView();
mv.setViewName("error");
if (e instanceof GlobalException){
GlobalException globalException = (GlobalException) e;
mv.addObject("ex",globalException.getMessage());
mv.addObject("msg","全局异常,错误码501....");
}else if (e instanceof RuntimeException){
RuntimeException runtimeException = (RuntimeException) e;
mv.addObject("ex",runtimeException.getMessage());
mv.addObject("msg","运行时异常,错误码601....");
}
return mv;
}
}
测试代码Controller层的改变
@ResponseBody
@RequestMapping("/load")
public Clazz load(HttpServletRequest req, Clazz clazz){
if(clazz.getCid() != null){
List lst = this.clazzBiz.listPager(clazz, null);
if (true)
throw new GlobalException("错误出现在 JsonController.load...");
return lst.get(0);
}
return null;
} 
使用@ControllerAdvice+@ExceptionHandler实现全局异常
package com.ruojuan.ssm.Exception;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.servlet.ModelAndView;
/**
* @author ruojuan
* @site 123456999
* @company 玉渊工作室
* @create 2022-08-22 18:10
*/
//@ControllerAdvice
public class GlobalExceptionResovler {
@ExceptionHandler
public ModelAndView handler(Exception e){
ModelAndView mv = new ModelAndView();
mv.setViewName("error");
if (e instanceof GlobalException){
GlobalException globalException = (GlobalException) e;
mv.addObject("ex",globalException.getMessage());
mv.addObject("msg","全局异常....");
}else if (e instanceof RuntimeException){
RuntimeException runtimeException = (RuntimeException) e;
mv.addObject("ex",runtimeException.getMessage());
mv.addObject("msg","运行时异常....");
}
return mv;
}
}
全局异常处理JSON返回
package com.ruojuan.ssm.Exception;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import java.util.HashMap;
import java.util.Map;
/**
* @author ruojuan
* @site 123456999
* @company 玉渊工作室
* @create 2022-08-22 18:11
*
* 当出现异常，统一向前端响应错误后出现的结果
*/
//@ControllerAdvice
@RestControllerAdvice
public class GlobalExceptionJsonResolver {
@ExceptionHandler
public Map handler(Exception e){
Map map = new HashMap();
if (e instanceof GlobalException){
GlobalException globalException = (GlobalException) e;
map.put("ex",globalException.getMessage());
map.put("msg","全局异常 GlobalExceptionResolver,错误码501....");
}else if (e instanceof RuntimeException){
RuntimeException runtimeException = (RuntimeException) e;
map.put("ex",runtimeException.getMessage());
map.put("msg","运行时异常 GlobalExceptionResolver,错误码601....");
}
return map;
}
}
