JSON和全局异常处理

zsm030616

于 2022-08-24 09:23:30 发布

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文章标签： json java spring

本文链接：https://blog.youkuaiyun.com/zsm030616/article/details/126497415

版权

一，JSON

JSON的形式：

{}-->json对象

[]-->json数组

常见的就是对象套数组：

{
        msg:""

        code:200,

        data[]

}--->json混合对象

2.SpringMVC框架如何产生上述三种格式的数据

1.导入pom依赖 -----------Jackson

2.配置（Spring-mvc.xml）适配器

        作用：做json数据的转换

3.使用注解@responseBody能够将任何数据转成json对象

1.导入pom依赖 -----------Jackson

<!--SpringMvc支持json的数据转换-->
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
      <version>2.9.3</version>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-core</artifactId>
      <version>2.9.3</version>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-annotations</artifactId>
      <version>2.9.3</version>
    </dependency>

2.配置（Spring-mvc.xml）适配器

这是固定的配置

<!--支持json数据返回的适配器-->
    <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
        <property name="messageConverters">
            <list>
                <ref bean="mappingJackson2HttpMessageConverter"/>
            </list>
        </property>
    </bean>
    <bean id="mappingJackson2HttpMessageConverter"
          class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
        <!--处理中文乱码以及避免IE执行AJAX时，返回JSON出现下载文件-->
        <property name="supportedMediaTypes">
            <list>
                <value>text/html;charset=UTF-8</value>
                <value>text/json;charset=UTF-8</value>
                <value>application/json;charset=UTF-8</value>
            </list>
        </property>
    </bean>

后台编写

package com.zhouzhou.ssm.controller;
 
import com.zhouzhou.ssm.Biz.ClazzBiz;
import com.zhouzhou.ssm.exception.GlobalException;
import com.zhouzhou.ssm.mapper.ClazzMapper;
import com.zhouzhou.ssm.model.Clazz;
import com.zhouzhou.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周周
 * @company zsm
 * @create  2022-08-22 20:39
 */
@RestController
@RequestMapping("clz/json")
public class JsonController {
 
    @Autowired
    private ClazzBiz clazzBiz;
 
 
    @RequestMapping("/clzEdit")
    public String clzEdit(){
        System.out.println("JsonController.clzEdit");
        return  "clzEdit";
    }
 
    //返回list<T>
    @RequestMapping("/list")
    public List<Clazz> list(HttpServletRequest request, Clazz clazz){
        PageBean pageBean = new PageBean();
        pageBean.setRequest(request);
        //自动返回json数组
        return this.clazzBiz.listPager(clazz,pageBean);
    }
 
 
    //返回list<Map>
    @RequestMapping("/listMap")
    public List<Map> listMap(HttpServletRequest request,Clazz clazz){
        PageBean pageBean = new PageBean();
        pageBean.setRequest(request);
        return this.clazzBiz.listMapPager(clazz,pageBean);
    }
 
    //返回Map
    @RequestMapping("/map")
    public Map map(HttpServletRequest request,Clazz clazz){
        PageBean pageBean = new PageBean();
        pageBean.setRequest(request);
        return this.clazzBiz.listMapPager(clazz,pageBean).get(0);
    }
 
    //返回T
    @RequestMapping("/load")
    public Clazz load(HttpServletRequest request,Clazz clazz){
        PageBean pageBean = new PageBean();
        pageBean.setRequest(request);
        return this.clazzBiz.listPager(clazz,pageBean).get(0);
    }
 
    //混合格式对象
    @RequestMapping("/hunhe")
    public Map hunhe(HttpServletRequest request,Clazz clazz){
        PageBean pageBean = new PageBean();
        pageBean.setRequest(request);
        List<Clazz> lst = this.clazzBiz.listPager(clazz, pageBean);
        Map map = new HashMap();
        map.put("data",lst);
        map.put("pagebean",pageBean);
        return map;
    }
}

解析：

@RequestMapping：窄化路径

@ResponseBody：区分注解（添加它后，会绕过本地视图解析器）

@ResponseBody+@Controller=@RestController

业务逻辑层

public List<Map> mapListPager(Clazz clazz,PageBean pageBean) {
        return clazzMapper.mapListPager(clazz);
    }

Mapper.xml(自动生成的xml文件)

<select id="mapListPager" parameterType="com.zking.ssm.model.Clazz" resultType="java.util.Map">
    select
    <include refid="Base_Column_List" />
    from t_struts_class
    <where>
      <if test="cname != null and cname != ''">
        cname like CONCAT('%',#{cname},'%')
      </if>
      <if test="cid != null and cid != ''">
        cid = #{cid}
      </if>
    </where>
  </select>

测试

建一个jsp界面

<%--
  Created by IntelliJ IDEA.
  User: zjjt
  Date: 2022/8/22
  Time: 18:16
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>测试json数据返回</title>
</head>
<body>
<a href="${pageContext.request.contextPath}/clz/json/list">返回list&lt;T&gt;对象</a><hr>
<a href="${pageContext.request.contextPath}/clz/json/listMap">返回list&lt;Map&gt;对象</a><hr>
<a href="${pageContext.request.contextPath}/clz/json/load?cid=1">返回T对象</a><hr>
<a href="${pageContext.request.contextPath}/clz/json/map?cid=1">返回Map对象</a><hr>
<a href="${pageContext.request.contextPath}/clz/json/hunhe">返回混合对象</a><hr>
</body>
</html>

《效果图》
在这里插入图片描述

二，Spring的全局异常处理

1.非全局异常处理问题演示
异常处理的三种形式：

    1.Springmvc.xml中进行统一配置及处理

    2.实现接口管理

    3.@ControllerAdvice

异常处理的思路：

参考images中的《springmvc全局异常处理思路.png》
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。

SpringMVC异常分类：

   使用Spring MVC提供的简单异常处理器SimpleMappingExceptionResolver
    实现Spring的异常处理接口HandlerExceptionResolver自定义自己的异常处理器；
    使用@ControllerAdvice + @ExceptionHandler

代码演示

@RequestMapping("/load")
    public Clazz load(HttpServletRequest request,Clazz clazz){
        PageBean pageBean = new PageBean();
        pageBean.setRequest(request);
        if(true)
            throw new GlobalException("系统繁忙，请参考E007；");
        return this.clazzBiz.listPager(clazz,pageBean).get(0);
    }

@Override
    public List<Map> listMapPager(Clazz clazz, PageBean pageBean) {
        if(true)
            throw  new RuntimeException("系统繁忙！异常存在于ClazzBizImpl中list方法");
        return clazzMapper.listMapPager(clazz);
    }

在这里插入图片描述
2，全局异常处理
SpringMVC自带的简单异常处理器

<!--统一异常处理-->
    <!-- springmvc提供的简单异常处理器 -->
    <bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
        <!-- 定义默认的异常处理页面 -->
        <property name="defaultErrorView" value="error"/>
        <!-- 定义异常处理页面用来获取异常信息的变量名，也可不定义，默认名为exception -->
        <property name="exceptionAttribute" value="ex"/>
        <!-- 定义需要特殊处理的异常，这是重要点 -->
        <property name="exceptionMappings">
            <props>
                <prop key="java.lang.RuntimeException">error</prop>
            </props>
            <!-- 还可以定义其他的自定义异常 -->
        </property>
    </bean>

出错时会自动跳到指定的jsp界面，怎么展示取决于以上配置如何配

<%--
  Created by IntelliJ IDEA.
  User: zjjt
  Date: 2022/8/22
  Time: 18:43
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>错误信息页面</title>
</head>
<body>
${msg}
<hr>
${ex}
</body>
</html>

通过HandlerExceptionResovler接口实现全局异常

提示：在运行之前需将SpringMVC中关于异常处理的配置取消掉

package com.zhouzhou.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周周
 * @company zsm
 * @create  2022-08-22 22:39
 */
//注释掉为了运行时不受它的影响
//@Component
public class GlobalHandlerExceptionResolver implements HandlerExceptionResolver {
 
    /**
     *
     * @param httpServletRequest
     * @param httpServletResponse
     * @param o 目标对象
     * @param e 目标对象执行，出现的异常对象
     * @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 exception =(GlobalException) e;//强转
            mv.addObject("ex",exception.getMessage());
            mv.addObject("msg","全局异常，错误码501");
        }else if(e instanceof RuntimeException){
            RuntimeException exception = (RuntimeException) e;
            mv.addObject("ex",exception.getMessage());
            mv.addObject("msg","运行时异常，错误码601");
        }
        return mv;
    }
}

测试代码的改变

 //返回T
    @RequestMapping("/load")
    public Clazz load(HttpServletRequest request,Clazz clazz){
        PageBean pageBean = new PageBean();
        pageBean.setRequest(request);
        if(true)
            throw new GlobalException("系统繁忙，请参考E007；");
        return this.clazzBiz.listPager(clazz,pageBean).get(0);
    }

jsp界面

<%--
  Created by IntelliJ IDEA.
  User: zjjt
  Date: 2022/8/22
  Time: 18:43
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>错误信息页面</title>
</head>
<body>
${msg}
<hr>
${ex}
</body>
</html>

《效果图》
在这里插入图片描述
使用@ControllerAdvice+@ExceptionHandler实现

package com.zhouzhou.ssm.exception;
 
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.servlet.ModelAndView;
 
**
 * @author周周
 * @company zsm
 * @create  2022-08-22 19:39
 */
@ControllerAdvice
public class GlobalExceptionResolver {
 
    @ExceptionHandler
    public ModelAndView hadler(Exception e){
        ModelAndView mv = new ModelAndView();
        mv.setViewName("error");
        if(e instanceof GlobalException){
            GlobalException exception =(GlobalException) e;//强转
            mv.addObject("ex",exception.getMessage());
            mv.addObject("msg","全局异常GlobalExceptionResolver，错误码501");
        }else if(e instanceof RuntimeException){
            RuntimeException exception = (RuntimeException) e;
            mv.addObject("ex",exception.getMessage());
            mv.addObject("msg","运行时异常GlobalExceptionResolver，错误码601");
        }
        return mv;
    }
 
}

在这里插入图片描述
全局异常处理JSON返回

package com.zhouzhou.ssm.exception;
 
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import org.springframework.web.servlet.ModelAndView;
 
import java.util.HashMap;
import java.util.Map;
 
 **
 * @author周周
 * @company zsm
 * @create  2022-08-22 19:39
 * 当出现异常，统一向前端响应错误信息的json对象数据
 */
 
@RestControllerAdvice
public class GlobalExceptionResolver2 {
 
    @ExceptionHandler
    public Map hadler(Exception e){
        Map map = new HashMap();
        if(e instanceof GlobalException){
            GlobalException exception =(GlobalException) e;//强转
            map.put("ex",exception.getMessage());
            map.put("msg","全局异常GlobalExceptionResolver，错误码501");
        }else if(e instanceof RuntimeException){
            RuntimeException exception = (RuntimeException) e;
            map.put("ex",exception.getMessage());
            map.put("msg","运行时异常GlobalExceptionResolver，错误码601");
        }
        return map;
    }
 
}

在这里插入图片描述