com.alibaba.mtc.MtContextCallable Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of multithread.context Show documentation
a simple lib for transmitting context between thread even using thread pool.
There is a newer version: 1.2.1
package com.alibaba.mtc;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.concurrent.atomic.AtomicReference;

/**
 * {@link MtContextCallable} decorate {@link Callable}, so as to get @{@link MtContextThreadLocal}
 * and transmit it to the time of {@link Callable} execution, needed when use {@link Callable} to thread pool.
 * 
 * Use factory method {@link #get(Callable)} to get decorated instance.
 *
 * @author ding.lid
 * @see java.util.concurrent.Executor
 * @see java.util.concurrent.ExecutorService
 * @see java.util.concurrent.ThreadPoolExecutor
 * @see java.util.concurrent.ScheduledThreadPoolExecutor
 * @see java.util.concurrent.Executors
 * @see java.util.concurrent.CompletionService
 * @see java.util.concurrent.ExecutorCompletionService
 * @since 0.9.0
 */
public final class MtContextCallable implements Callable {
    private final AtomicReference, Object>> copiedRef;
    private final Callable callable;
    private final boolean releaseMtContextAfterCall;


    private MtContextCallable(Callable callable, boolean releaseMtContextAfterCall) {
        this.callable = callable;
        this.releaseMtContextAfterCall = releaseMtContextAfterCall;
        this.copiedRef = new AtomicReference, Object>>(MtContextThreadLocal.copy());
    }

    /**
     * wrap method {@link Callable#call()}.
     */
    @Override
    public V call() throws Exception {
        Map, Object> copied = copiedRef.get();
        if (copied == null || releaseMtContextAfterCall && !copiedRef.compareAndSet(copied, null)) {
            throw new IllegalStateException("MtContext is released!");
        }

        Map, Object> backup = MtContextThreadLocal.backupAndSet(copied);
        try {
            return callable.call();
        } finally {
            MtContextThreadLocal.restore(backup);
        }
    }

    public Callable getCallable() {
        return callable;
    }

    /**
     * Factory method, wrapper input {@link Callable} to {@link MtContextCallable}.
     * 

     * This method is idempotent.
     *
     * @param callable input {@link Callable}
     * @return Wrapped {@link Callable}
     */
    public static  MtContextCallable get(Callable callable) {
        return get(callable, false);
    }

    /**
     * Factory method, wrapper input {@link Callable} to {@link MtContextCallable}.
     * 
     * This method is idempotent.
     *
     * @param callable                  input {@link Callable}
     * @param releaseMtContextAfterCall release MtContext after run, avoid memory leak even if {@link MtContextRunnable} is referred.
     * @return Wrapped {@link Callable}
     */
    public static  MtContextCallable get(Callable callable, boolean releaseMtContextAfterCall) {
        if (null == callable) {
            return null;
        }

        if (callable instanceof MtContextCallable) { // avoid redundant decoration, and ensure idempotency
            return (MtContextCallable) callable;
        }
        return new MtContextCallable(callable, releaseMtContextAfterCall);
    }

    /**
     * wrapper input {@link Callable} Collection to {@link MtContextCallable} Collection.
     *
     * @param tasks task to be wrapped
     * @return Wrapped {@link Callable}
     */
    public static  List> gets(Collection> tasks) {
        return gets(tasks, false);
    }

    /**
     * wrapper input {@link Callable} Collection to {@link MtContextCallable} Collection.
     *
     * @param tasks                     task to be wrapped
     * @param releaseMtContextAfterCall release MtContext after run, avoid memory leak even if {@link MtContextRunnable} is referred.
     * @return Wrapped {@link Callable}
     */
    public static  List> gets(Collection> tasks, boolean releaseMtContextAfterCall) {
        if (null == tasks) {
            return null;
        }
        List> copy = new ArrayList>();
        for (Callable task : tasks) {
            copy.add(MtContextCallable.get(task, releaseMtContextAfterCall));
        }
        return copy;
    }
}