Springmcv json转换控制

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

<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>

   Springmvc.xml配置

<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<T>
     * @param req
     * @param clazz
     * @return
     */
    @RequestMapping("/list")
    public List<Clazz> 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<Clazz> 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<Clazz> 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<Map>
     * @param req
     * @param clazz
     * @return
     */
    @RequestMapping("/mapList")
    public List<Map> mapList(HttpServletRequest req, Clazz clazz){
        PageBean pageBean = new PageBean();
        pageBean.setRequest(req);
        List<Map> lst = this.clazzBiz.listMapPager(clazz, pageBean);
        return lst;
    }

    /**
     * 返回Map
     * @param req
     * @param clazz
     * @return
     */
    @RequestMapping("/mapLoad")
    public Map mapLoad(HttpServletRequest req, Clazz clazz){
        if(clazz.getCid() != null){
            List<Map> lst = this.clazzBiz.listMapPager(clazz, null);
            return lst.get(0);
        }
        return null;
    }


    @RequestMapping("/all")
    public Map all(HttpServletRequest req, Clazz clazz){
        PageBean pageBean = new PageBean();
        pageBean.setRequest(req);
        List<Clazz> lst = this.clazzBiz.listPager(clazz, pageBean);
        Map map = new HashMap();
        map.put("lst",lst);
        map.put("pageBean",pageBean);
        return map;
    }

    @RequestMapping("/jsonStr")
    public String jsonStr(HttpServletRequest req, Clazz clazz){
        return "Edit";
    }


}

servic层 ：

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

 Mapper.xml

<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：

<%--
  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" %>
<html>
<head>
    <title>测试json数据返回</title>
</head>
<body>

<a href="${pageContext.request.contextPath}/clz/json/list">返回list<T>对象</a><hr>
<a href="${pageContext.request.contextPath}/clz/json/mapList">返回list<Map>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/mapLoad?cid=1">返回Map对象</a><hr>
<a href="${pageContext.request.contextPath}/clz/json/all">返回混合对象</a><hr>

</body>
</html>

 效果：

 

 

 

 

二，SpringMVC 的全局异常处理

        1.为什么要全局异常处理

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<T>
     * @param req
     * @param clazz
     * @return
     */
    @ResponseBody
    @RequestMapping("/list")
    public List<Clazz> 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<Clazz> lst = this.clazzBiz.listPager(clazz, pageBean);
        return lst;
    }



   /**
     * 返回List<Map>
     * @param req
     * @param clazz
     * @return
     */
    @ResponseBody
    @RequestMapping("/mapList")
    public List<Map> mapList(HttpServletRequest req, Clazz clazz){
        PageBean pageBean = new PageBean();
        pageBean.setRequest(req);
        List<Map> lst = this.clazzBiz.listMapPager(clazz, pageBean);
        return lst;
    }

Bizimpl:

@Override
    public List<Map> listMapPager(Clazz clazz, PageBean pageBean) {
        if(true) {
            throw new RuntimeException("查询班级信息异常，异常存在于ClazzBizImpl.list方法");
        }
        return clazzMapper.listMapPager(clazz);
    }

效果： 

 

SpringMVC自带的简单异常处理器

        springmvc-servlet.xml

<!-- 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>

error.jsp

<body>

${ex}

</body>

 

 

  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<Clazz> 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;
    }

}