SpringBoot3和4的版本新特性及升级要点详解

// 1. 声明接口：像定义Controller一样定义要调用的远程服务
@HttpExchange(url = "/api/v1", accept = "application/json", contentType = "application/json")
public interface UserServiceClient {
    @GetExchange("/users/{id}")
    User getUserById(@PathVariable Long id);
    
    @PostExchange("/users")
    User createUser(@RequestBody User user);
}

// 2. 配置Bean：通过工厂创建代理实例
@Configuration
class ClientConfig {
    @Bean
    UserServiceClient userServiceClient(WebClient.Builder builder) {
        WebClient webClient = builder.baseUrl("http://user-service-host").build();
        return HttpServiceProxyFactory.builder(WebClientAdapter.forClient(webClient))
                                      .build()
                                      .createClient(UserServiceClient.class);
    }
}

// 3. 直接使用：像注入普通Bean一样注入并使用
@Service
public class OrderService {
    @Autowired
    private UserServiceClient userServiceClient; // 注入声明的客户端
    
    public Order getOrderWithUser(Long orderId, Long userId) {
        User user = userServiceClient.getUserById(userId); // 直接调用，如同本地方法
        // ... 处理订单逻辑
        return order;
    }
}

// 当抛出异常时，Spring Boot 3.0 默认可以生成如下结构的JSON响应
// 传统的自定义错误格式：{"message": "用户不存在", "error": "Not Found"}
// 新的标准Problem Detail格式：
{
    "type": "about:blank",
    "title": "Not Found",
    "status": 404,
    "detail": "用户ID为123的用户不存在",
    "instance": "/users/123"
}

// 使用记录类 (Records) 作为DTO或值对象：自动生成构造器、getter、equals、hashCode和toString
public record UserDTO(Long id, String name, String email) {} // 一行顶过去几十行

// 使用密封类 (Sealed Classes) 精确控制继承层次，增强领域模型安全性
public sealed interface PaymentResult permits PaymentSuccess, PaymentFailed {
    // 只允许这两个类实现此接口
}
public record PaymentSuccess(String transactionId) implements PaymentResult {}
public record PaymentFailed(String errorCode) implements PaymentResult {}

<!-- 在pom.xml中，使用Spring Boot插件即可轻松构建原生镜像 -->
<plugin>
    <groupId>org.graalvm.buildtools</groupId>
    <artifactId>native-maven-plugin</artifactId>
</plugin>

# 使用Maven命令编译成本地可执行文件
mvn -Pnative native:compile
# 编译后生成一个独立的二进制文件（如`myapp`），可以直接运行
./target/myapp

@RestController
@RequestMapping("/api/user")
public class UserController {
    @GetMapping(version = "1")
    public UserV1 getUserV1() {
        // 返回旧版数据模型
        return new UserV1("张三");
    }
    @GetMapping(version = "2")
    public UserV2 getUserV2() {
        // 返回新版数据模型，包含更多字段
        return new UserV2("张三", "zhangsan@example.com");
    }
}

# application.yml
spring:
  threads:
    virtual:
      enabled: true  # 全局启用虚拟线程支持

import org.springframework.beans.factory.BeanRegistrar;
import org.springframework.beans.factory.BeanRegistry;
import org.springframework.core.env.Environment;

public class MyModuleRegistrar implements BeanRegistrar {
    @Override
    public void register(BeanRegistry registry, Environment environment) {
        // 批量注册一批相关的Bean
        registry.registerBean("serviceA", MyServiceA.class);
        registry.registerBean("serviceB", MyServiceB.class);
        // 根据环境属性动态注册Bean
        if (environment.matchesProfiles("cluster")) {
            registry.registerBean("clusterService", ClusterService.class);
        }
    }
}

// 1. 声明接口
public interface UserServiceClient {
    @GetExchange("/users/{id}")
    User getUserById(@PathVariable Long id);
}
// 2. 创建代理并注入
@Service
public class OrderService {
    private final UserServiceClient userServiceClient;
    public OrderService(UserServiceClient userServiceClient) {
        this.userServiceClient = userServiceClient; // 像使用本地Bean一样调用
    }
}

import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

public class UserService {
    // 参数name明确标记为可空，返回值明确标记为非空
    public @NonNull User createUser(@Nullable String name) {
        return new User(name != null ? name : "Guest");
    }
}