AOP 拦截线程池执行新线程，保证上下文在父子线程间传递

小灰灰 2022-03-11 07:17 220阅读 0赞

该项目已合并到 git项目[microservice-sc-v1.0][] dev分支中，具体位置为microservice-sc-v1.0/module-service-hi/src/main/java/servicehi/asyncthreadaop/，假如对您的需求有帮助，可不可以不吝给颗star，您的肯定是我的动力。

从朋友那里借鉴来的思路，他当时遇到的业务情况是这样的：

每个用户登陆系统后，该用户需要异步执行多个方法，方法内涉及到从securityContext和LogContext中读取用户信息

抽象出来便是

用户登录的主线程需要异步(多子线程)执行多个方法，方法中需要保持用户的上下文信息

解决思路：

aop拦截子线程的调用，将上下文通过封装的Runnable对象传递给子线程。因为aop是beanPostProcessor后处理器，只能拦截1)bean中的2)方法，所以逆推得 子线程来自 一个2)线程池的submit执行合适一些，而且这个线程池对象是1)一个bean。

实现：

1、bean形式存在的线程池

@Configuration
    public class AsynExecutor {
    	
    	@Bean
    	@Lazy
    	public ExecutorService defaultExecutor() {
    		return Executors.newCachedThreadPool();
    	}
    
    }

2、该线程池提供的线程可以通过注解的方式被业务方法体异步使用

@Async("defaultExecutor")
    @Target({ElementType.METHOD,ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface DefaultAsyncThread {
    
    	
    }

3、标注如上注解的方法在被线程池中线程执行时添加AOP

public class DefaultExecutorSubmitAspect {
    
    	@Around("execution(* java.util.concurrent.Executor.*(..))")
    	@SneakyThrows
    	public Object intercept(ProceedingJoinPoint joinPoint) {
    		
    		Object[] args = joinPoint.getArgs();
    		for(int i =0; i< args.length; i++) {
    			args[i] = processArgs(args[i]);
    		}
    		
    		return joinPoint.proceed();
    	}
    	
    	Object processArgs(Object arg) {
    		if(arg instanceof Runnable) {
    			Runnable r = (Runnable)arg;
    			return new RunnableWeave(r);
    		}
    		if(arg instanceof Callable<?>) {
    			Callable<?> c = (Callable<?>)arg;
    			return new CallableWeave<>(c);
    		}
    		if(arg instanceof Collection<?>) {
    			Collection<?> cs = (Collection<?>)arg;
    			List<Object> collect = cs.stream().map(this::processArgs).collect(Collectors.toList());
    			return collect;
    		}
    		return arg;
    	}
    }

4、将上下文传递给子线程，从而保证 子线程里可以读取用户登录信息(父线程上下文信息)

public class RunnableWeave  implements Runnable {
    
    	private final Runnable r;
    	private final Map<String, String> MDCContextMap;
    	private final SecurityContext securityContext;
    	
    	public RunnableWeave(Runnable r) {
    		this.r = r;
    		this.MDCContextMap = MDC.getCopyOfContextMap();
    		securityContext = SecurityContextHolder.getContext();
    	}
    	
    	@Override
    	public void run() {
    		MDC.setContextMap(MDCContextMap);
    		SecurityContextHolder.setContext(securityContext);
    		r.run();
    		SecurityContextHolder.clearContext();
    		MDC.setContextMap(new HashMap<>());
    	}
    
    }

public class CallableWeave<V> implements Callable<V> {
    
    	private final Callable<V> c;
    	private final Map<String, String> MDCContextMap;
    	private final SecurityContext securityContext;
    	
    	public CallableWeave(Callable<V> c) {
    		this.c = c;
    		this.MDCContextMap = MDC.getCopyOfContextMap();
    		this.securityContext = SecurityContextHolder.getContext();
    	}
    	@Override
    	public V call() throws Exception {
    		MDC.setContextMap(MDCContextMap);
    		SecurityContextHolder.setContext(securityContext);
    		V v = c.call();
    		MDC.setContextMap(new HashMap<>());
    		SecurityContextHolder.clearContext();
    		return v;
    	}
    
    }

[microservice-sc-v1.0]: https://github.com/linfujian/microservice-sc-v1.0