Java Spring Boot — 用户管理 CRUD API

目标

使用 Spring Boot 3 + Spring Data JPA + H2 构建完整的用户管理 REST API。

完整代码

//─── User.java (Entity) ───
package com.example.demo.entity;

import jakarta.persistence.*;

@Entity
@Table(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(nullable = false)
    private String name;

    @Column(nullable = false, unique = true)
    private String email;

    public User() {}
    public User(String name, String email) {
        this.name = name;
        this.email = email;
    }

    // getters & setters ...
    public Long getId() { return id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public String getEmail() { return email; }
    public void setEmail(String email) { this.email = email; }
}

//─── UserRepository.java ───
package com.example.demo.repository;

import com.example.demo.entity.User;
import org.springframework.data.jpa.repository.JpaRepository;

public interface UserRepository extends JpaRepository<User, Long> {
}

//─── UserController.java ───
package com.example.demo.controller;

import com.example.demo.entity.User;
import com.example.demo.repository.UserRepository;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

import java.util.List;

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

    private final UserRepository repo;

    public UserController(UserRepository repo) {
        this.repo = repo;
    }

    @GetMapping
    public List<User> getAll() {
        return repo.findAll();
    }

    @GetMapping("/{id}")
    public ResponseEntity<User> getById(@PathVariable Long id) {
        return repo.findById(id)
            .map(ResponseEntity::ok)
            .orElse(ResponseEntity.notFound().build());
    }

    @PostMapping
    public ResponseEntity<User> create(@RequestBody User user) {
        User saved = repo.save(user);
        return ResponseEntity
            .created(java.net.URI.create("/api/users/" + saved.getId()))
            .body(saved);
    }

    @PutMapping("/{id}")
    public ResponseEntity<User> update(@PathVariable Long id, @RequestBody User user) {
        return repo.findById(id).map(existing -> {
            existing.setName(user.getName());
            existing.setEmail(user.getEmail());
            return ResponseEntity.ok(repo.save(existing));
        }).orElse(ResponseEntity.notFound().build());
    }

    @DeleteMapping("/{id}")
    public ResponseEntity<Void> delete(@PathVariable Long id) {
        if (!repo.existsById(id)) return ResponseEntity.notFound().build();
        repo.deleteById(id);
        return ResponseEntity.noContent().build();
    }
}

# application.properties
spring.datasource.url=jdbc:h2:mem:userdb
spring.h2.console.enabled=true
spring.jpa.show-sql=true
spring.jpa.hibernate.ddl-auto=update

<!-- pom.xml 附加依赖 -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <scope>runtime</scope>
</dependency>

测试

curl http://localhost:8080/api/users

curl -X POST http://localhost:8080/api/users \
  -H "Content-Type: application/json" \
  -d '{"name":"Alice","email":"alice@example.com"}'

curl -X PUT http://localhost:8080/api/users/1 \
  -H "Content-Type: application/json" \
  -d '{"name":"Alice Updated","email":"alice@example.com"}'

curl -X DELETE http://localhost:8080/api/users/1

要点说明

• JpaRepository<User, Long> 自动提供 findAll()、findById()、save()、deleteById() 等方法
• 构造函数注入优于 @Autowired 字段注入
• H2 内存数据库适合开发测试，生产需切换 MySQL/PostgreSQL
• ResponseEntity 提供完整的 HTTP 响应控制（状态码、头、体）