使用 Spring 在 java 中为 RESTful API 创建端点的最佳方法

Question

I'm new to the field, trying to create an API using Spring with Maven dependencies such as Project Lombok, just to get more hands on with my learning.

So i've managed to write some code to start the application and now i'm creating some endpoints. The first of them was a "list users" type of thing that my brother helped me with, it's divided in 3 classes that i'll list below:

(1) UserListResponse.java:

package com.tropicalia.meu_cardapio.api.user.list;

import lombok.Data;

@Data
public class UserListResponse {

    private Long id;

    private String name;

    private String email;

}

(2) UserListRest.java

package com.tropicalia.meu_cardapio.api.user.list;

import com.tropicalia.meu_cardapio.domain.user.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
@RequestMapping("/users")
public class UserListRest {

    @Autowired
    UserListService service;

    @GetMapping
    public ResponseEntity<List<User>> list() {
        return ResponseEntity.ok().body(service.listUsers());
    }
}

(3) UserListService.java

package com.tropicalia.meu_cardapio.api.user.list;

import com.tropicalia.meu_cardapio.domain.user.User;
import com.tropicalia.meu_cardapio.domain.user.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class UserListService {

    @Autowired
    UserRepository repository;

    public List<User> listUsers() {
        List<User> list = repository.findAll();
        return list;
    }
}

The reason i'm writing this post is that i do not know how to create the other endpoints such as "create user" and i don't even know where to start with my research, would be very grateful if someone could help me with some guidance here.

Answer 1

One of the approaches I use is to group controller in so-called resources, like:

• User Resource
• Book Resource etc

Then you may create one controller, called UserController with mapping on controller level, and some specific mappings in method level like:

@RestController
@RequestMapping("/users")
public class UserController{

    @GetMapping
    public ResponseEntity<List<UserDto>> getUsers(){}

    @GetMapping("/{id}")
    public ResponseEntity<UserDto> getOneUser(@PathVariable Long id){}

    @PostMapping
    public ResponseEntity<UserDto> addUser(@RequestBody UserDto user){}

    @PutMapping("/{id}")
    public ResponseEntity<UserDto> updateUser(@PathVariable Long id, @RequestBody UserDto user){}

}

Then you can use the service/repository layer with spring data JPA to read/persist your data. The good starting points are spring guides like:

• https://spring.io/guides/gs/serving-web-content/
• https://spring.io/guides/gs/accessing-data-jpa/

Answer 2

First of all, maybe is better just define more generic endpoints and not UserList, usually is better just define the User endpoint and add there all methods and routes like listUsers or getUser, addUser...

Furthermore when you use @Repository it generates the basic methods to "get add delete or update" your object.

For example you can define inside your Service

public User saveUser(User user) {
    if (user != null) {
        return repository.save(user);
    } else {
        return null;
    }
}

And in your Controller:

@PostMapping("/addUser")
public User addUser(@Valid @RequestBody User user) {

    user newUser = service.saveUser(user);

    return newUser;
}

Tell me if you have more doubts. :D