Shulou(Shulou.com)06/03 Report--

Catalogue

The thought of exception handling

Test environment preparation

Two ways of exception handling

Method 1: simple exception handler

Method 2: custom exception handlers

Summary

The thought of exception handling

Test environment preparation

First write a class in the DemoController control layer as the controller for test access

Package com.itheima.controller;import com.itheima.exception.MyException;import com.itheima.service.DemoService;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.RequestParam;import java.io.FileNotFoundException;@Controllerpublic class DemoController {@ Autowired private DemoService demoService @ RequestMapping (value= "/ show") public String show () throws FileNotFoundException, MyException {System.out.println ("show running"); demoService.show1 (); / / demoService.show2 (); / / demoService.show3 (); / / demoService.show4 (); / / demoService.show5 (); return "index";}}

Then write the interface DemoService and the implementation class DemoServiceImpl in service

Package com.itheima.service;import com.itheima.exception.MyException;import java.io.FileNotFoundException;public interface DemoService {public void show1 (); public void show2 (); public void show3 () throws FileNotFoundException;public void show4 (); public void show5 () throws MyException;} package com.itheima.service.impl;import com.itheima.exception.MyException;import com.itheima.service.DemoService;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.InputStream Public class DemoServiceImpl implements DemoService {public void show1 () {System.out.println ("type conversion exception"); Object str = "zhangsan"; Integer num = (Integer) str;} public void show2 () {System.out.println ("divide by zero exception"); int I = 1 / 0 } public void show3 () throws FileNotFoundException {System.out.println ("file cannot find exception"); InputStream in = new FileInputStream ("C:/xxx/xxx/xxx.txt");} public void show4 () {System.out.println ("null pointer exception"); String str = null; str.length () } public void show5 () throws MyException {System.out.println ("Custom exception"); throw new MyException ();}}

The MyException is a custom exception and is declared under another package of itheima. There is no implementation at this time:

Visit / show, because the show1 method called first will report a type conversion exception:

The environment is ready.

Two ways of exception handling

Method 1: simple exception handler

Method 1 is very simple, just configure the corresponding configuration file:

Then access it again, and you can see that you jump to the error view:

Method 2: custom exception handlers

Steps

1. Create an exception handler class to implement HandlerExceptionResolver

2. Configure exception handlers

3. Write the exception page

4. Test abnormal jump

Demo

Step 1: create an exception handler class to implement HandlerExceptionResolver

Package com.itheima.resolver;import com.itheima.exception.MyException;import org.springframework.web.servlet.HandlerExceptionResolver;import org.springframework.web.servlet.ModelAndView;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse Public class MyExceptionResolver implements HandlerExceptionResolver {/ * this is the method parameter Exception: exception object return value ModelAndView: jump to error view information * / public ModelAndView resolveException (HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) {ModelAndView md = new ModelAndView () / * this is just a rough demonstration of code logic and will not be written like this in actual development. The following demonstration just tells us that we can judge exception information in this method * / if (e instanceof MyException) {md.addObject ("info", "custom exception") } else if (e instanceof ClassCastException) {md.addObject ("info", "type conversion exception");} md.setViewName ("error"); return md;}}

Step 2: configure the exception handler in the configuration file of SpringMVC

Just test the interview.

Summary

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