今天，Java已经卷到“屎上雕花”的程度，八股文的准备如果仅仅靠背诵，很容易陷入“背了忘，忘了背”的死循环中。
所以，我们必须：结合具体的代码demo，尝试系统地掌握，才能更好的卷出一条活路。
1. 日志记录
记录方法的执行时间、参数和返回值。
@Aspect
@Component
public class LoggingAspect {
@Around("execution(* com.example.service.*.*(..))")
public Object logExecutionTime(ProceedingJoinPoint joinPoint) throws Throwable {
long start = System.currentTimeMillis();
Object proceed = joinPoint.proceed();
long executionTime = System.currentTimeMillis() - start;
System.out.println(joinPoint.getSignature() + " executed in " + executionTime + "ms");
return proceed;
}
}
@Service
public class MyService {
public void perform() {
System.out.println("Performing service...");
}
}
2. 权限检查
在方法执行前进行权限验证，防止未经授权的访问。
@Aspect
@Component
public class SecurityAspect {
@Before("execution(* com.example.service.*.*(..)) && @annotation(com.example.security.Secured)")
public void checkSecurity(JoinPoint joinPoint) {
// 这里进行权限检查逻辑
System.out.println("Checking security for " + joinPoint.getSignature().getName());
}
}
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Secured {
String role() default "USER";
}
@Service
public class MyService {
@Secured(role = "ADMIN")
public void performAdminTask() {
System.out.println("Performing admin task...");
}
public void perform() {
System.out.println("Performing service...");
}
}
3. 事务管理
自动管理事务的开启、提交和回滚。
@Aspect
@Component
public class TransactionAspect {
@Around("execution(* com.example.service.*.*(..))")
public Object manageTransaction(ProceedingJoinPoint joinPoint) throws Throwable {
System.out.println("Transaction start");
try {
Object result = joinPoint.proceed();
System.out.println("Transaction commit");
return result;
} catch (Exception ex) {
System.out.println("Transaction rollback due to: " + ex.getMessage());
throw ex;
}
}
}
@Service
public class MyService {
public void performTransaction() {
System.out.println("Performing transactional service...");
// 模拟异常
if (true) throw new RuntimeException("Transaction failed");
}
}
4. 异常处理
统一处理方法执行时的异常。
@Aspect
@Component
public class ExceptionHandlingAspect {
@AfterThrowing(pointcut = "execution(* com.example.service.*.*(..))", throwing = "ex")
public void handleException(JoinPoint joinPoint, Exception ex) {
System.out.println("Exception in " + joinPoint.getSignature().getName() + " with message: " + ex.getMessage());
// 这里可以记录日志、通知管理员等
}
}
@Service
public class MyService {
public void perform() {
System.out.println("Performing service...");
throw new RuntimeException("Unexpected error");
}
}
5. 缓存管理
在方法执行前检查缓存，在执行后更新缓存。
@Aspect
@Component
public class CachingAspect {
private Map<String, Object> cache = new HashMap<>();
@Around("execution(* com.example.service.*.*(..)) && @annotation(com.example.cache.Cacheable)")
public Object cacheResult(ProceedingJoinPoint joinPoint) throws Throwable {
String key = joinPoint.getSignature().toString();
if (cache.containsKey(key)) {
System.out.println("Returning cached result for " + key);
return cache.get(key);
}
Object result = joinPoint.proceed();
cache.put(key, result);
System.out.println("Caching result for " + key);
return result;
}
}
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Cacheable {
}
@Service
public class MyService {
@Cacheable
public String getData() {
System.out.println("Fetching data from database...");
return "Data from DB";
}
}
总结：
Spring AOP 在实际项目中广泛用于日志记录、权限检查、事务管理、异常处理和缓存管理等场景。这些示例展示了如何通过切面简化和增强应用程序的业务逻辑。
Coding不易，棒棒，加油！
