Spring Boot入门：快速构建应用

概述

Spring Boot是Spring框架的快速开发工具，它简化了Spring应用的配置和部署。本教程介绍Spring Boot的核心概念和使用方法。

1. Spring Boot应用结构

my-app/
├── src/
│   ├── main/
│   │   ├── java/
│   │   │   └── com/example/myapp/
│   │   │       ├── MyAppApplication.java
│   │   │       ├── controller/
│   │   │       ├── service/
│   │   │       ├── repository/
│   │   │       └── model/
│   │   └── resources/
│   │       ├── application.properties
│   │       ├── static/
│   │       └── templates/
│   └── test/
└── pom.xml

2. 创建第一个应用

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.*;

@SpringBootApplication
@RestController
public class MyAppApplication {
    
    public static void main(String[] args) {
        SpringApplication.run(MyAppApplication.class, args);
    }
    
    @GetMapping("/")
    public String hello() {
        return "Hello, Spring Boot!";
    }
    
    @GetMapping("/greet/{name}")
    public String greet(@PathVariable String name) {
        return "Hello, " + name + "!";
    }
}

3. 配置文件

# application.properties
server.port=8080
spring.application.name=my-app

# 数据库配置
spring.datasource.url=jdbc:mysql://localhost:3306/mydb
spring.datasource.username=root
spring.datasource.password=password
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

# JPA配置
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true

4. REST API

import org.springframework.web.bind.annotation.*;
import org.springframework.http.ResponseEntity;
import java.util.List;

@RestController
@RequestMapping("/api/users")
public class UserController {
    
    private final UserService userService;
    
    public UserController(UserService userService) {
        this.userService = userService;
    }
    
    @GetMapping
    public List<User> getAllUsers() {
        return userService.findAll();
    }
    
    @GetMapping("/{id}")
    public ResponseEntity<User> getUserById(@PathVariable Long id) {
        return userService.findById(id)
            .map(ResponseEntity::ok)
            .orElse(ResponseEntity.notFound().build());
    }
    
    @PostMapping
    public User createUser(@RequestBody User user) {
        return userService.save(user);
    }
    
    @PutMapping("/{id}")
    public ResponseEntity<User> updateUser(@PathVariable Long id, @RequestBody User user) {
        return userService.findById(id)
            .map(existing -> {
                user.setId(id);
                return ResponseEntity.ok(userService.save(user));
            })
            .orElse(ResponseEntity.notFound().build());
    }
    
    @DeleteMapping("/{id}")
    public ResponseEntity<Void> deleteUser(@PathVariable Long id) {
        return userService.findById(id)
            .map(existing -> {
                userService.deleteById(id);
                return ResponseEntity.ok().<Void>build();
            })
            .orElse(ResponseEntity.notFound().build());
    }
}

5. 数据访问

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

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

import org.springframework.stereotype.Service;
import java.util.Optional;

@Service
public class UserService {
    private final UserRepository userRepository;
    
    public UserService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }
    
    public List<User> findAll() {
        return userRepository.findAll();
    }
    
    public Optional<User> findById(Long id) {
        return userRepository.findById(id);
    }
    
    public User save(User user) {
        return userRepository.save(user);
    }
    
    public void deleteById(Long id) {
        userRepository.deleteById(id);
    }
}

6. 最佳实践

1. 使用自动配置：充分利用Spring Boot的自动配置
2. 使用application.properties：集中管理配置
3. 使用Spring Data JPA：简化数据访问
4. 使用RESTful API：设计规范的接口
5. 使用Spring Boot Actuator：监控应用状态

总结

Spring Boot简化了Spring应用的开发和部署。掌握Spring Boot的核心概念，可以快速构建企业级应用。