ThreadLocal加切面实现线程级别的方法缓存

1、实现效果

当一个请求线程多次请求A方法时,只会触发一次A方法的实际调用,会将方法结果缓存起来,避免多次调用。

2、实现过程

1. 需要一个注解ThreadLocalCache,在需要缓存的方法上加上该注解
2. 需要一个切面,借助ThreadLocal,将结果缓存起来,利用环绕通知来实现方法拦截从缓存中返回方法执行结果

3、代码实现

3.1、ThreadLocalCache注解创建

作用于方法级别

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface ThreadLocalCache {
}

3.2、ThreadLocalTestAspect切面创建

@Aspect
@Component
public class ThreadLocalTestAspect {private ThreadLocal<Map<Object, Object>> threadLocal = new ThreadLocal<>();@Around("@annotation(com.example.test.ThreadLocalCache)")private Object myPointcut(ProceedingJoinPoint proceedingJoinPoint) {//获取方法的入参Object[] args = proceedingJoinPoint.getArgs();Signature signature = proceedingJoinPoint.getSignature();//获取目标方法名String name = signature.getName();//获取目标方法的类的完全限定名String declaringTypeName = signature.getDeclaringTypeName();//生成缓存keyObject key = SimpleKeyGenerator.generateKey(args, declaringTypeName, name);if (Objects.isNull(threadLocal.get())) {threadLocal.set(new HashMap<>(8));}try {if (!threadLocal.get().containsKey(key)) {threadLocal.get().put(key, proceedingJoinPoint.proceed());}} catch (Throwable e) {//日志记录e.printStackTrace();}return threadLocal.get().get(key);}public void removeThreadLocal(){threadLocal.remove();}}

4、测试过程

创建一个接口及实现

public interface ThreadLocalTestService {Long getParentIdByName(String name);
}

@Service
public class ThreadLocalTestServiceImpl implements ThreadLocalTestService{@ThreadLocalCache@Overridepublic Long getParentIdByName(String name) {//根据name查询父级IDSystem.out.println("com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了");return 666L;}
}

方法调用

@RestController
@RequestMapping("/ThreadLocalTest")
public class ThreadLocalTest {@Autowiredprivate ThreadLocalTestService threadLocalTestService;@Autowiredprivate ThreadLocalTestAspect threadLocalTestAspect;@GetMapping("getParentIdByName")public Long getParentIdByName(String name){System.out.println(Thread.currentThread().getName());threadLocalTestService.getParentIdByName(name);threadLocalTestService.getParentIdByName(name);Long parentId = threadLocalTestService.getParentIdByName(name);threadLocalTestAspect.removeThreadLocal();return parentId;}}

3.执行结果

http-nio-8087-exec-1
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-2
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-4
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-5
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-6
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-7
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-8
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-10
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-9
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-3
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-1
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-2
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了

http-nio-8087-exec-是线程名字,可以看到http-nio-8087-exec-1执行了两次,每次都调用四次getParentIdByName 方法,但getParentIdByName 方法实际至执行了一次,剩下的三次是从缓存中获取的。
这里需要注意的是:线程每次结束的时候都需要调用threadLocalTestAspect.removeThreadLocal();为的是把当前线程threadLocal里的缓存抹掉,因为同一个线程可能会被重复使用,所以不抹掉,可能会导致多次请求使用同一个线程,目标方法只会执行一次,和我们的最初的实现效果是违背的。
下面是不调用threadLocalTestAspect.removeThreadLocal();的执行结果

http-nio-8087-exec-1
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-3
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-8
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-5
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-6
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-7
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-4
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-9
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-10
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-2
com.example.test.ThreadLocalTestServiceImpl.getParentIdByName 执行了
http-nio-8087-exec-1
http-nio-8087-exec-3
http-nio-8087-exec-8
http-nio-8087-exec-5