一文解析SpringBoot到底强在哪

// SpringBoot自动根据classpath中的jar包、已定义的bean等条件
// 自动配置相应的组件
@EnableAutoConfiguration  // 启用自动配置
// 例如：当classpath中有HSQLDB时，自动配置内存数据库

<!-- 示例：添加Web Starter -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- 数据库 Starter -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <!-- 排除 Tomcat -->
    <exclusions>
        <exclusion>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<!-- 切换为 Jetty -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jetty</artifactId>
</dependency>
<!-- 或切换为 Undertow -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-undertow</artifactId>
</dependency>

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

@SpringBootApplication(
    scanBasePackages = "com.example",  // 扫描包路径
    exclude = {DataSourceAutoConfiguration.class},  // 排除自动配置
    scanBasePackageClasses = {UserService.class}  // 扫描特定类所在包
)

@SpringBootTest()
class ApplicationTests {
    @Test
    void contextLoads() {
      //测试代码
    }
}

@Configuration
public class AppConfig {
    @Bean
    public ObjectMapper objectMapper() {
        return new ObjectMapper();
    }
}

@Component
public class OrderService {
    @Autowired
    private UserRepository userRepository;  // 字段注入
    @Autowired
    private ProductRepository productRepository;
}

@Component
public class AppConfig {
    // 1. 注入简单字符串
    @Value("${app.name}")
    private String appName;
    // 2. 注入数字
    @Value("${app.port:8080}")  // 默认值
    private int port;
    // 3. 注入布尔值
    @Value("${app.enabled:true}")
    private boolean enabled;
    // 4. 注入浮点数
    @Value("${app.version:1.0}")
    private double version;
}

@RestController
@RequestMapping("/api/v1/users")  // 类级别路径前缀
public class UserController {
    // 完整路径: /api/v1/users
    @GetMapping
    public List<User> getUsers() {
        return userService.findAll();
    }
    // 完整路径: /api/v1/users/{id}
    @GetMapping("/{id}")
    public User getUser(@PathVariable Long id) {
        return userService.findById(id);
    }
}

@RestController
public class SimpleController {
    // 映射到 /hello
    @RequestMapping("/hello")
    public String hello() {
        return "Hello World";
    }
    // 映射到 /greet
    @RequestMapping(value = "/greet", method = RequestMethod.GET)
    public String greet() {
        return "Greetings!";
    }
}

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/demo_db
    username: demo_user
    password: demo_pass
    driver-class-name: com.mysql.cj.jdbc.Driver

@Service
public class UserService {
    @Autowired
    private UserRepository userRepository;
    // 创建用户
    public User createUser(User user) {
        return userRepository.save(user);
    }
    // 查询用户
    public User getUserById(Long id) {
        return userRepository.findById(id)
                .orElseThrow(() -> new UserNotFoundException("用户不存在"));
    }
    // 更新用户
    public User updateUser(Long id, User userDetails) {
        User user = getUserById(id);
        user.setUsername(userDetails.getUsername());
        user.setEmail(userDetails.getEmail());
        return userRepository.save(user);
    }
    // 删除用户
    public void deleteUser(Long id) {
        userRepository.deleteById(id);
    }
    // 查询所有用户
    public List<User> getAllUsers() {
        return userRepository.findAll();
    }
}

@RestController
@RequestMapping("/api/v1/users")
public class UserController {
    // GET /api/v1/users
    @GetMapping
      // 获取所有用户
    // GET /api/v1/users/{id}
    @GetMapping("/{id}")
        // 根据ID获取用户
    // POST /api/v1/users
    @PostMapping
        // 创建用户
    // PUT /api/v1/users/{id}
    @PutMapping("/{id}")
        // 更新用户
    // DELETE /api/v1/users/{id}
    @DeleteMapping("/{id}")
        // 删除用户
}