"Method not allowed", 405 problem analysis and solution

First , Be clear 405 The problem is the browser side （ Or client ） The request method is inconsistent with the processing method of the server for processing the request of this path .

background ：SpringBoot2.70 Integrate JPA, Addition, deletion, modification and query of test sheet table

The phenomenon ： In use postman test delete Method encountered
Of

chart 1： postman Test screenshot

chart 2： Back end code block

package com.xxxx.salesforecast.Controller;

import com.xxxx.salesforecast.pojo.User;
import com.xxxx.salesforecast.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;


import java.util.List;


/** *  User external interface  * * @author : liuke * @date : 2022-06-22 14:20 **/
@RestController
@RequestMapping("/user")
public class UserController {
    

    @Autowired
    private UserRepository userRepository;

    /** *  Insert  * * @param user * @return */
    @PostMapping
    public String addUser(@RequestBody User user) {
    
        userRepository.save(user);
        return "success";
    }

    /** *  Query all  * * @return */
    @GetMapping("")
    public List<User> getAllUser() {
    
        List<User> userList = userRepository.findAll();
        return userList;
    }

    /** *  according to  id  Delete  * @param id * @return */
    @DeleteMapping("/{id}")
    public String deleteUserById(@PathVariable Integer id){
    
        userRepository.deleteById(id.intValue());
        return "success";
    }

}

Figure 3 ： Console error

Troubleshooting process ：
First step ： Check your code roughly , I feel OK , Start Baidu
The second step ： The first plan Baidu got , Unresolved
application.yml Add
spring mvc: hiddenmethod: filter: enabled: true
This starts HiddenHttpMethodFilter filter , To support the browser can send DELETE PUT request . And I don't send requests with my browser , It's about using postman, So useless is also normal .

The third step ： Try to @DeleteMapping Change to @RequestMapping, Unresolved

Step four ： Try to get rid of @PathVariable annotation , Unresolved

Step five ： The thought of , I use it restful Interface , The paths for adding, deleting, and modifying queries are the same , adopt @PostMapping、@PutMapping、@DeleteMapping、@GeMapping To distinguish behaviors .

So the path of the method is modified , Not yet. . But it is not reported at this time 405 了 , Start reporting 404 了 .
404, As we all know, there must be no matching path .

Then I finally found the problem , Path below
http://localhost:6060/user/delete?id=1
there id It is in the form of parameter transmission
and @DeleteMapping(“/delete/{id}”) It means id When the path

So the path is changed to

reflection ： Why did you report it before 405 The error? ？
Because it matches the query interface , This interface is @GetMapping, So and @DeleteMapping Don't agree with each other , Just report it 405 error .

And this interface does not need to pass parameters , If the parameter is passed, no error will be reported , such as , We visit http://baidu.com and http://baidu.com/?sbbaidu=1 It's the same

summary ： The problem is that I put @DeleteMapping(“/{id}”) Of id When the path and path parameters are confused .