SpringMVC ---- 异常

异常处理

异常处理器（实现接口的方式：一般不用）【了解】注解实现异常处理 项目异常处理方案【理解】

自定义异常将异常包装为自定义异常统一处理异常异常中文乱码问题

异常处理器中的中文处理controller中的中文处理

该方式处理的异常是在接受参数之后的异常

package com.itheima.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;

@Component
public class ExceptionResolver implements HandlerExceptionResolver {
    @Override
    public ModelAndView resolveException(HttpServletRequest request,
                                         HttpServletResponse response,
                                         Object handler,
                                         Exception ex) {
        System.out.println("my exception is running ...."+ex);
        ModelAndView modelAndView = new ModelAndView();
        if( ex instanceof NullPointerException){
            modelAndView.addObject("msg","空指针异常");
        }else if ( ex instanceof  ArithmeticException){
            modelAndView.addObject("msg","算数运算异常");
        }else{
            modelAndView.addObject("msg","未知的异常");
        }
        modelAndView.setViewName("error.jsp");
        return modelAndView;
    }
}

error.jsp

<%--异常消息展示页面--%>
<%@page pageEncoding="UTF-8" language="java" contentType="text/html;UTF-8" %>

${msg}

该处理方式是在 核心控制器加载的时候就加载了，所以可以拦截到参数中的异常

package com.itheima.exception;

import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;

@Component
//使用注解开发异常处理器
//声明该类是一个Controller的通知类，声明后该类就会被加载成异常处理器
//可以在controller的前后做功能增强
@ControllerAdvice
public class ExceptionAdvice {

    //类中定义的方法携带@ExceptionHandler注解的会被作为异常处理器，后面添加实际处理的异常类型
    @ExceptionHandler(NullPointerException.class)
    @ResponseBody
    public String doNullException(Exception ex){
        return "空指针异常";
    }

    @ExceptionHandler(ArithmeticException.class)
    @ResponseBody
    public String doArithmeticException(Exception ex){
        return "ArithmeticException";
    }

    @ExceptionHandler(Exception.class)
    @ResponseBody
    public String doException(Exception ex){
        return "all";
    }

}

业务异常(用户) BusinessException

package com.itheima.exception;
//自定义异常继承RuntimeException，覆盖父类所有的构造方法
public class BusinessException extends RuntimeException {
    public BusinessException() {
    }

    public BusinessException(String message) {
        super(message);
    }

    public BusinessException(String message, Throwable cause) {
        super(message, cause);
    }

    public BusinessException(Throwable cause) {
        super(cause);
    }

    public BusinessException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
        super(message, cause, enableSuppression, writableStackTrace);
    }
}

系统异常： SystemException

package com.itheima.exception;
//自定义异常继承RuntimeException，覆盖父类所有的构造方法
public class SystemException extends RuntimeException {
    public SystemException() {
    }

    public SystemException(String message) {
        super(message);
    }

    public SystemException(String message, Throwable cause) {
        super(message, cause);
    }

    public SystemException(Throwable cause) {
        super(cause);
    }

    public SystemException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
        super(message, cause, enableSuppression, writableStackTrace);
    }
}

其他异常: DevelopException

package com.itheima.exception;
//自定义异常继承RuntimeException，覆盖父类所有的构造方法
public class DevelopException extends RuntimeException {
    public DevelopException() {
    }

    public DevelopException(String message) {
        super(message);
    }

    public DevelopException(String message, Throwable cause) {
        super(message, cause);
    }

    public DevelopException(Throwable cause) {
        super(cause);
    }

    public DevelopException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
        super(message, cause, enableSuppression, writableStackTrace);
    }
}

    public void save(){
        //业务层中如果出现了异常，就对出现异常的代码进行try...catch...处理
        //在catch中将出现的异常包装成自定义异常，同时务必将当前异常对象传入自定义异常，避免真正的异常信息消失
        try {
            throw new SQLException();
        } catch (SQLException e) {
            throw new SystemException("数据库连接超时！",e);
        }
    }

package com.itheima.exception;

import org.springframework.stereotype.Component;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;

@Component
@ControllerAdvice
public class ProjectExceptionAdvice {

    @ExceptionHandler(BusinessException.class)
    @ResponseBody()
    public String doBusinessException(Exception ex, Model m){
        //使用参数Model将要保存的数据传递到页面上，功能等同于ModelAndView
        //业务异常出现的消息要发送给用户查看
//        m.addAttribute("msg",ex.getMessage());
        return ex.getMessage();
    }

    @ExceptionHandler(value = {SystemException.class})
    @ResponseBody
    public String doSystemException(Exception ex, Model m){
        //系统异常出现的消息不要发送给用户查看，发送统一的信息给用户看
//        m.addAttribute("msg","服务器出现问题，请联系管理员！");
        //实际的问题现象应该传递给redis服务器，运维人员通过后台系统查看
        //实际的问题显现更应该传递给redis服务器，运维人员通过后台系统查看
        return "服务器出现问题，请联系管理员！";
    }

    @ExceptionHandler(Exception.class)
    @ResponseBody
    public String doException(Exception ex, Model m){
//        m.addAttribute("msg",ex.getMessage());
        //将ex对象保存起来
        return ex.getMessage();
    }

}

推荐博客
https://www.jianshu.com/p/b87ffc816903
https://blog.csdn.net/Numb_ZL/article/details/122273878

比较推荐的方法是

  
        
        
            
                
                    
                        text/plain;charset=utf-8
                        text/html;charset=UTF-8
                    
                
            
        
    

https://www.cnblogs.com/userzf/p/13824972.html

@RequestMapping(value = "/pets/{petId}", method = RequestMethod.GET, produces="application/json")  
@ResponseBody  
public Pet getPet(@PathVariable String petId, Model model) {     
    // implementation omitted  
}  


//由于添加了ResponseBody所以可以省略调 produces="application/json"
@RequestMapping(value = "/pets/{petId}", method = RequestMethod.GET)  
@ResponseBody  
public Pet getPet(@PathVariable String petId, Model model) {     
    // implementation omitted  
}  

produces：添加处理后的编码
consumes：添加请求类型限制

    @PostMapping(value="/out",produces="application/json;charset=UTF-8,text/html;charset=UTF-8",consumes="application/json")
    @ResponseBody
    public String outInfo(@RequestBody User user) {

        return "我是中文";
    }