快速入门：第一个 Spring Boot 应用

从一个简单的 CRUD 应用开始，快速体验 Spring Boot 的开发流程。

项目初始化

使用 Spring Initializr 创建项目，添加以下依赖：

<dependencies>
    <!-- Web 支持 -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <!-- 数据库支持 -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>

    <!-- H2 内存数据库（开发测试用） -->
    <dependency>
        <groupId>com.h2database</groupId>
        <artifactId>h2</artifactId>
        <scope>runtime</scope>
    </dependency>

    <!-- Lombok（简化代码） -->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
</dependencies>

application.yml 配置：

spring:
  datasource:
    url: jdbc:h2:mem:testdb
    driver-class-name: org.h2.Driver
    username: sa
    password:
  h2:
    console:
      enabled: true
      path: /h2-console
  jpa:
    hibernate:
      ddl-auto: create-drop
    show-sql: true

实体类

package com.example.demo.entity;

import jakarta.persistence.*;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.AllArgsConstructor;
import java.time.LocalDateTime;

@Entity
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(nullable = false, length = 50)
    private String name;

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

    private Integer age;

    private LocalDateTime createdAt;

    @PrePersist
    protected void onCreate() {
        this.createdAt = LocalDateTime.now();
    }
}

Repository 层

package com.example.demo.repository;

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

public interface UserRepository extends JpaRepository<User, Long> {
    List<User> findByName(String name);
    List<User> findByAgeGreaterThan(Integer age);
}

Service 层

package com.example.demo.service;

import com.example.demo.entity.User;
import com.example.demo.repository.UserRepository;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Service;
import java.util.List;

@Service
@RequiredArgsConstructor
public class UserService {

    private final UserRepository userRepository;

    public List<User> findAll() {
        return userRepository.findAll();
    }

    public User findById(Long id) {
        return userRepository.findById(id)
                .orElseThrow(() -> new RuntimeException("User not found: " + id));
    }

    public User create(User user) {
        return userRepository.save(user);
    }

    public User update(Long id, User user) {
        User existing = findById(id);
        existing.setName(user.getName());
        existing.setEmail(user.getEmail());
        existing.setAge(user.getAge());
        return userRepository.save(existing);
    }

    public void delete(Long id) {
        userRepository.deleteById(id);
    }
}

Controller 层

package com.example.demo.controller;

import com.example.demo.entity.User;
import com.example.demo.service.UserService;
import lombok.RequiredArgsConstructor;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.*;

import java.util.List;

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

    private final UserService userService;

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

    @GetMapping("/{id}")
    public User getById(@PathVariable Long id) {
        return userService.findById(id);
    }

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public User create(@RequestBody User user) {
        return userService.create(user);
    }

    @PutMapping("/{id}")
    public User update(@PathVariable Long id, @RequestBody User user) {
        return userService.update(id, user);
    }

    @DeleteMapping("/{id}")
    @ResponseStatus(HttpStatus.NO_CONTENT)
    public void delete(@PathVariable Long id) {
        userService.delete(id);
    }
}

测试 API

# 创建用户
curl -X POST http://localhost:8080/users \
  -H "Content-Type: application/json" \
  -d '{"name":"张三","email":"zhangsan@example.com","age":25}'

# 查询所有用户
curl http://localhost:8080/users

# 查询单个用户
curl http://localhost:8080/users/1

# 更新用户
curl -X PUT http://localhost:8080/users/1 \
  -H "Content-Type: application/json" \
  -d '{"name":"张三丰","email":"zhangsf@example.com","age":30}'

# 删除用户
curl -X DELETE http://localhost:8080/users/1

也可以通过 http://localhost:8080/h2-console 查看数据库内容。

三层架构体系

Controller（表现层）
    ↓ 接收请求，返回响应
Service（业务层）
    ↓ 业务逻辑
Repository（数据访问层）
    ↓ 数据库操作
Database

各层职责

层	注解	职责
Controller	@RestController	接收 HTTP 请求、参数校验、返回结果
Service	@Service	业务逻辑、事务管理、调用 Repository
Repository	@Repository	数据库 CRUD 操作

练习

1. 添加一个 Article 实体（title, content, author, createdAt）
2. 实现 Article 的完整 CRUD API
3. 在 User 中添加一个获取用户文章列表的接口