从零搭建自己的SpringBoot后台框架(五)

约定不等于承诺〃 2023-08-17 15:29 79阅读 0赞

### 一：为什么需要定义全局异常 ###

在互联网时代，我们所开发的应用大多是直面用户的，程序中的任何一点小疏忽都可能导致用户的流失，而程序出现异常往往又是不可避免的，所以我们需要对异常进行捕获，然后给予相应的处理，来减少程序异常对用户体验的影响

### 二：添加业务类异常 ###

在前面说过的ret文件夹下创建ServiceException

package com.example.demo.core.ret;
    
    import java.io.Serializable;
    
    /**
     * @author phubing
     * @Description:
     * @time 2019/4/18 11:39
     */
    public class ServiceException extends RuntimeException implements Serializable{
    
       private static final long serialVersionUID = 1213855733833039552L;
    
       public ServiceException() {
       }
    
       public ServiceException(String message) {
          super(message);
       }
    
       public ServiceException(String message, Throwable cause) {
          super(message, cause);
       }
    }

### 三：添加异常处理配置 ###

打开[上篇文章][Link 1]创建的WebConfigurer，添加如下方法

@Override
    public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers) {
        exceptionResolvers.add(getHandlerExceptionResolver());
    }
    
    /**
     * 创建异常处理
     * @return
     */
    private HandlerExceptionResolver getHandlerExceptionResolver(){
        HandlerExceptionResolver handlerExceptionResolver = new HandlerExceptionResolver(){
            @Override
            public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response,
                                                 Object handler, Exception e) {
                RetResult<Object> result = getResuleByHeandleException(request, handler, e);
                responseResult(response, result);
                return new ModelAndView();
            }
        };
        return handlerExceptionResolver;
    }
    
    /**
     * 根据异常类型确定返回数据
     * @param request
     * @param handler
     * @param e
     * @return
     */
    private RetResult<Object> getResuleByHeandleException(HttpServletRequest request, Object handler, Exception e){
        RetResult<Object> result = new RetResult<>();
        if (e instanceof ServiceException) {
            result.setCode(RetCode.FAIL).setMsg(e.getMessage()).setData(null);
            return result;
        }
        if (e instanceof NoHandlerFoundException) {
            result.setCode(RetCode.NOT_FOUND).setMsg("接口 [" + request.getRequestURI() + "] 不存在");
            return result;
        }
        result.setCode(RetCode.INTERNAL_SERVER_ERROR).setMsg("接口 [" + request.getRequestURI() + "] 内部错误，请联系管理员");
        String message;
        if (handler instanceof HandlerMethod) {
            HandlerMethod handlerMethod = (HandlerMethod) handler;
            message = String.format("接口 [%s] 出现异常，方法：%s.%s，异常摘要：%s", request.getRequestURI(),
                    handlerMethod.getBean().getClass().getName(), handlerMethod.getMethod() .getName(), e.getMessage());
        } else {
            message = e.getMessage();
        }
        LOGGER.error(message, e);
        return result;
    }
    
    /**
     * @Title: responseResult
     * @Description: 响应结果
     * @param response
     * @param result
     * @Reutrn void
     */
    private void responseResult(HttpServletResponse response, RetResult<Object> result) {
        response.setCharacterEncoding("UTF-8");
        response.setHeader("Content-type", "application/json;charset=UTF-8");
        response.setStatus(200);
        try {
            response.getWriter().write(JSON.toJSONString(result,SerializerFeature.WriteMapNullValue));
        } catch (IOException ex) {
            LOGGER.error(ex.getMessage());
        }
    }

### 四：添加配置文件 ###

**Spring Boot 中, 当用户访问了一个不存在的链接时, Spring 默认会将页面重定向到 \*\*/error\*\* 上, 而不会抛出异常. **

既然如此, 那我们就告诉 Spring Boot, 当出现 404 错误时, 抛出一个异常即可.

在 `application.properties` 中添加两个配置:

`spring.mvc.throw-exception-if-no-handler-found=true`

`spring.resources.add-mappings=false `

上面的配置中, 第一个 `spring.mvc.throw-exception-if-no-handler-found `告诉 SpringBoot 当出现 404 错误时, 直接抛出异常. 第二个 `spring.resources.add-mappings` 告诉 SpringBoot 不要为我们工程中的资源文件建立映射.

### 五：创建测试接口 ###

package com.example.demo.service.impl;
    
    import com.example.demo.core.ret.ServiceException;
    import com.example.demo.dao.UserInfoMapper;
    import com.example.demo.model.UserInfo;
    import com.example.demo.service.UserInfoService;
    import org.springframework.stereotype.Service;
    
    import javax.annotation.Resource;
    import java.util.List;
    
    /**
     * @author phubing
     * @Description:
     * @time 2019/4/18 11:39
     */
    @Service
    public class UserInfoServiceImpl implements UserInfoService{
    
        @Resource
        private UserInfoMapper userInfoMapper;
    
        @Override
        public UserInfo selectById(Integer id){
            UserInfo userInfo = userInfoMapper.selectById(id);
            if(userInfo == null){
                throw new ServiceException("暂无该用户");
            }
            return userInfo;
        }
    }

*UserInfoController.java*

package com.example.demo.controller;
    
    import com.example.demo.core.ret.RetResponse;
    import com.example.demo.core.ret.RetResult;
    import com.example.demo.core.ret.ServiceException;
    import com.example.demo.model.UserInfo;
    import com.example.demo.service.UserInfoService;
    import org.springframework.web.bind.annotation.PostMapping;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    import javax.annotation.Resource;
    import java.util.List;
    
    /**
     * @author phubing
     * @Description:
     * @time 2019/4/18 11:39
     */
    @RestController
    @RequestMapping("userInfo")
    public class UserInfoController {
    
        @Resource
        private UserInfoService userInfoService;
    
        @PostMapping("/hello")
        public String hello(){
            return "hello SpringBoot";
        }
    
        @PostMapping("/selectById")
        public RetResult<UserInfo> selectById(Integer id){
            UserInfo userInfo = userInfoService.selectById(id);
            return RetResponse.makeOKRsp(userInfo);
        }
    
        @PostMapping("/testException")
        public RetResult<UserInfo> testException(Integer id){
            List a = null;
            a.size();
            UserInfo userInfo = userInfoService.selectById(id);
            return RetResponse.makeOKRsp(userInfo);
        }
    
    
    }

### 六：接口测试 ###

访问`192.168.1.104:8080/userInfo/selectById`参数 `id:3`

{
        "code": 400,
        "data": null,
        "msg": "暂无该用户"
    }

访问`192.168.1.104:8080/userInfo/testException`

{
        "code": 500,
        "data": null,
        "msg": "接口 [/userInfo/testException] 内部错误，请联系管理员"
    }

## ##

[Link 1]: https://juejin.im/post/5ad811e66fb9a0460138ceb1