Spring Boot常用注解说明

// 自定义自动配置：仅在类路径存在 Redis 且用户未自定义时创建
@Configuration
@ConditionalOnClass(RedisOperations.class)
@ConditionalOnMissingBean(RedisTemplate.class)
@EnableConfigurationProperties(RedisProperties.class)
public class RedisAutoConfiguration {

    @Bean
    @ConditionalOnProperty(name = "spring.redis.enabled", havingValue = "true", matchIfMissing = true)
    public RedisTemplate<Object, Object> redisTemplate(RedisConnectionFactory factory) {
        RedisTemplate<Object, Object> template = new RedisTemplate<>();
        template.setConnectionFactory(factory);
        return template;
    }
}

import org.aspectj.lang.annotation.*;
import org.aspectj.lang.ProceedingJoinPoint;

@Aspect
@Component
public class LoggingAspect {

    // 定义切点：匹配 Service 层所有方法
    @Pointcut("execution(* com.example.service.*.*(..))")
    public void serviceLayer() {}

    // 前置通知：方法执行前记录入参
    @Before("serviceLayer()")
    public void logBefore(JoinPoint joinPoint) {
        String method = joinPoint.getSignature().getName();
        Object[] args = joinPoint.getArgs();
        System.out.println("[BEFORE] " + method + " called with args: " + Arrays.toString(args));
    }

    // 后置通知：方法返回后记录结果
    @AfterReturning(pointcut = "serviceLayer()", returning = "result")
    public void logAfter(JoinPoint joinPoint, Object result) {
        System.out.println("[AFTER] " + joinPoint.getSignature().getName() + " returned: " + result);
    }

    // 环绕通知：计算方法执行时间
    @Around("serviceLayer()")
    public Object measureExecutionTime(ProceedingJoinPoint pjp) throws Throwable {
        long start = System.currentTimeMillis();
        Object result = pjp.proceed(); // 执行目标方法
        long elapsed = System.currentTimeMillis() - start;
        System.out.println("[PERF] " + pjp.getSignature().getName() + " took " + elapsed + "ms");
        return result;
    }

    // 异常通知：捕获并记录异常
    @AfterThrowing(pointcut = "serviceLayer()", throwing = "ex")
    public void logException(JoinPoint joinPoint, Throwable ex) {
        System.err.println("[ERROR] Exception in " + joinPoint.getSignature().getName() + ": " + ex.getMessage());
    }
}

@Service
public class OrderService {
    @Autowired
    private OrderService self; // 注入代理对象

    public void createOrder() {
        self.validateStock(); // 通过代理调用，AOP 生效
    }

    @Transactional
    public void validateStock() { /* ... */ }
}

@Service
public class PaymentService {

    @Transactional(propagation = Propagation.REQUIRED)  // 默认：加入现有事务，无则新建
    public void processPayment() { /* ... */ }

    @Transactional(propagation = Propagation.REQUIRES_NEW)  // 挂起当前事务，新建独立事务
    public void auditLog() { /* ... */ }

    @Transactional(propagation = Propagation.NESTED)  // 嵌套事务，可独立回滚
    public void retryOperation() { /* ... */ }

    @Transactional(propagation = Propagation.MANDATORY)  // 必须在已有事务中调用
    public void internalOperation() { /* ... */ }
}

@Entity
@Table(name = "users", indexes = @Index(columnList = "email", unique = true))
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(nullable = false, length = 100)
    private String username;

    @Column(unique = true)
    private String email;

    @OneToMany(mappedBy = "user", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    private List<Order> orders = new ArrayList<>();

    @CreationTimestamp
    private LocalDateTime createdAt;

    @UpdateTimestamp
    private LocalDateTime updatedAt;
}

@EnableGlobalMethodSecurity(prePostEnabled = true, securedEnabled = true)
@Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {
    // 启用 @PreAuthorize、@PostAuthorize、@Secured
}

@Service
public class OrderService {

    // 只有 ADMIN 或订单所有者才能查看
    @PreAuthorize("hasRole('ADMIN') or #orderId == authentication.principal.id")
    public Order getOrder(Long orderId) { /* ... */ }

    // 返回后校验：确保用户只能看到自己的数据
    @PostAuthorize("returnObject.userId == authentication.principal.id")
    public Order getOrderById(Long orderId) { /* ... */ }

    // 只接受特定角色
    @Secured("ROLE_MANAGER")
    public void refundOrder(Long orderId) { /* ... */ }

    // 批量操作前过滤：只处理当前用户有权限的数据
    @PreFilter("filterObject.userId == authentication.principal.id")
    public void batchUpdate(List<Order> orders) { /* ... */ }
}

@EnableAsync
@EnableScheduling
@SpringBootApplication
public class MyApp { /* ... */ }

@Service
public class NotificationService {

    // 异步发送邮件，不阻塞主线程
    @Async("emailTaskExecutor")  // 指定自定义线程池
    public CompletableFuture<String> sendEmail(String to, String subject, String body) {
        // 模拟发送耗时 2 秒
        try { Thread.sleep(2000); } catch (InterruptedException e) { Thread.currentThread().interrupt(); }
        return CompletableFuture.completedFuture("Email sent to " + to);
    }

    // 每 5 分钟执行一次数据清理
    @Scheduled(cron = "0 */5 * * * *")
    public void cleanupExpiredData() {
        System.out.println("Running cleanup at " + LocalDateTime.now());
    }

    // 应用启动后延迟 10 秒执行，之后每 30 秒执行
    @Scheduled(initialDelay = 10000, fixedRate = 30000)
    public void healthCheck() { /* ... */ }
}

// 自定义线程池配置
@Configuration
public class AsyncConfig {
    @Bean("emailTaskExecutor")
    public Executor emailTaskExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(5);
        executor.setMaxPoolSize(20);
        executor.setQueueCapacity(100);
        executor.setThreadNamePrefix("email-");
        executor.initialize();
        return executor;
    }
}

// application.yml
// app:
//   mail:
//     host: smtp.example.com
//     port: 587
//     username: noreply@example.com

@ConfigurationProperties(prefix = "app.mail")
@Component
@Data  // Lombok
public class MailProperties {
    @NotBlank
    private String host;

    @Min(1)
    @Max(65535)
    private int port;

    @Email
    private String username;

    @Pattern(regexp = "^(plain|ssl|tls)$")
    private String security = "tls";
}

// 使用 JSR-303 注解校验配置属性
@Validated
@ConfigurationProperties(prefix = "app.mail")
public class MailProperties { /* ... */ }