[AOP]5.Spring AOPで提供される様々なAsppects-合併制御

/**
 * Interceptor that throttles concurrent access, blocking invocations if a specified concurrency
 * limit is reached.
 *
 * 

 * Can be applied to methods of local services that involve heavy use of system resources, in a
 * scenario where it is more efficient to throttle concurrency for a specific service rather than
 * restricting the entire thread pool (e.g. the web container's thread pool).
 *
 * 

 * The default concurrency limit of this interceptor is 1. Specify the "concurrencyLimit" bean
 * property to change this value.
 *
 * @author Juergen Hoeller
 * @since 11.02.2004
 * @see #setConcurrencyLimit
 */
@SuppressWarnings("serial")
public class ConcurrencyThrottleInterceptor extends ConcurrencyThrottleSupport
    implements MethodInterceptor, Serializable {

  public ConcurrencyThrottleInterceptor() {
    setConcurrencyLimit(1);
  }

  @Override
  public Object invoke(MethodInvocation methodInvocation) throws Throwable {
    beforeAccess();
    try {
      return methodInvocation.proceed();
    } finally {
      afterAccess();
    }
  }

}

protected void beforeAccess() {
  if (this.concurrencyLimit == NO_CONCURRENCY) {
    throw new IllegalStateException(
        "Currently no invocations allowed - concurrency limit set to NO_CONCURRENCY");
  }
  if (this.concurrencyLimit > 0) {
    boolean debug = logger.isDebugEnabled();
    synchronized (this.monitor) {
      boolean interrupted = false;
      while (this.concurrencyCount >= this.concurrencyLimit) {
        if (interrupted) {
          throw new IllegalStateException(
              "Thread was interrupted while waiting for invocation access, "
                  + "but concurrency limit still does not allow for entering");
        }
        if (debug) {
          logger.debug("Concurrency count " + this.concurrencyCount + " has reached limit "
              + this.concurrencyLimit + " - blocking");
        }
        try {
          this.monitor.wait();
        } catch (InterruptedException ex) {
          // Re-interrupt current thread, to allow other threads to react.
          Thread.currentThread().interrupt();
          interrupted = true;
        }
      }
      if (debug) {
        logger.debug("Entering throttle at concurrency count " + this.concurrencyCount);
      }
      this.concurrencyCount++;
    }
  }
}

protected void afterAccess() {
  if (this.concurrencyLimit >= 0) {
    synchronized (this.monitor) {
      this.concurrencyCount--;
      if (logger.isDebugEnabled()) {
        logger.debug("Returning from throttle at concurrency count " + this.concurrencyCount);
      }
      this.monitor.notify();
    }
  }
}

@Bean
public Advisor throttleAdvisor() {
  AspectJExpressionPointcut pointcut = new AspectJExpressionPointcut();
  pointcut.setExpression(
      "execution(* (@org.springframework.stereotype.Service *).doThrottleThings(..))");

  return new DefaultPointcutAdvisor(pointcut, concurrencyThrottleInterceptor());
}

@Bean
public ConcurrencyThrottleInterceptor concurrencyThrottleInterceptor() {
  ConcurrencyThrottleInterceptor interceptor = new ConcurrencyThrottleInterceptor();
  interceptor.setConcurrencyLimit(3);
  return interceptor;
}

public void doThrottleThings() throws InterruptedException {
    System.out.println(Thread.currentThread().getName() + ": is doing something, needing 5s");
    Thread.sleep(5000);
  }

@Test
public void testConcurrencyThrottle() throws InterruptedException {
  IntStream.range(0, 5).forEach(i -> {
    new Thread(() -> {
      try {
        service.doThrottleThings();
      } catch (Exception e) {
        e.printStackTrace();
      }
    }).start();
  });

  Thread.sleep(10000);
}

[Thread-4] DEBUG o.s.a.i.ConcurrencyThrottleInterceptor - Entering throttle at concurrency count 0
[Thread-5] DEBUG o.s.a.i.ConcurrencyThrottleInterceptor - Entering throttle at concurrency count 1
[Thread-6] DEBUG o.s.a.i.ConcurrencyThrottleInterceptor - Entering throttle at concurrency count 2
[Thread-3] DEBUG o.s.a.i.ConcurrencyThrottleInterceptor - Concurrency count 3 has reached limit 3 - blocking
[Thread-2] DEBUG o.s.a.i.ConcurrencyThrottleInterceptor - Concurrency count 3 has reached limit 3 - blocking
Thread-4: is doing something, needing 5s
Thread-5: is doing something, needing 5s
Thread-6: is doing something, needing 5s
[Thread-4] DEBUG o.s.a.i.ConcurrencyThrottleInterceptor - Returning from throttle at concurrency count 2
[Thread-3] DEBUG o.s.a.i.ConcurrencyThrottleInterceptor - Entering throttle at concurrency count 2
Thread-3: is doing something, needing 5s
[Thread-6] DEBUG o.s.a.i.ConcurrencyThrottleInterceptor - Returning from throttle at concurrency count 2
[Thread-5] DEBUG o.s.a.i.ConcurrencyThrottleInterceptor - Returning from throttle at concurrency count 1
[Thread-2] DEBUG o.s.a.i.ConcurrencyThrottleInterceptor - Entering throttle at concurrency count 1
Thread-2: is doing something, needing 5s

/**
 * Permit any number of concurrent invocations: that is, don't throttle concurrency.
 */
public static final int UNBOUNDED_CONCURRENCY = ConcurrencyThrottleSupport.UNBOUNDED_CONCURRENCY;

/**
 * Switch concurrency 'off': that is, don't allow any concurrent invocations.
 */
public static final int NO_CONCURRENCY = ConcurrencyThrottleSupport.NO_CONCURRENCY;

/** Internal concurrency throttle used by this executor */
private final ConcurrencyThrottleAdapter concurrencyThrottle = new ConcurrencyThrottleAdapter();

/**
 * Subclass of the general ConcurrencyThrottleSupport class, making {@code beforeAccess()} and
 * {@code afterAccess()} visible to the surrounding class.
 */
private static class ConcurrencyThrottleAdapter extends ConcurrencyThrottleSupport {

  @Override
  protected void beforeAccess() {
    super.beforeAccess();
  }

  @Override
  protected void afterAccess() {
    super.afterAccess();
  }
}

@Override
public void execute(Runnable task, long startTimeout) {
  Assert.notNull(task, "Runnable must not be null");
  Runnable taskToUse = (this.taskDecorator != null ? this.taskDecorator.decorate(task) : task);
  if (isThrottleActive() && startTimeout > TIMEOUT_IMMEDIATE) {
    this.concurrencyThrottle.beforeAccess();
    doExecute(new ConcurrencyThrottlingRunnable(taskToUse));
  } else {
    doExecute(taskToUse);
  }
}

public interface TaskDecorator {

    /**
     * Decorate the given {@code Runnable}, returning a potentially wrapped
     * {@code Runnable} for actual execution.
     * @param runnable the original {@code Runnable}
     * @return the decorated {@code Runnable}
     */
    Runnable decorate(Runnable runnable);

}

public boolean isThrottleActive() {
  return (this.concurrencyLimit > 0);
}

/**
 * This Runnable calls {@code afterAccess()} after the target Runnable has finished its execution.
 */
private class ConcurrencyThrottlingRunnable implements Runnable {

  private final Runnable target;

  public ConcurrencyThrottlingRunnable(Runnable target) {
    this.target = target;
  }

  @Override
  public void run() {
    try {
      this.target.run();
    } finally {
      concurrencyThrottle.afterAccess();
    }
  }
}