Callable+ThreadPoolExecutor实现多线程并发并获得返回值

前言
经常会遇到一些性能问题，比如调用某个接口，可能要循环调用100次，并且需要拿到每一次调用的返回结果，通常我们都是放在for循环中一次次的串行调用，这种方式可想而知道有多慢，那怎么解决这个问题呢？

多线程
为了解决以上问题，我使用的方式是多线程。多线程常规的有两种实现方式，即继承Tread类，实现Runnable接口，但是这两种实现方式，有一个共同的问题，就是没有返回值，对于我们来说，获得每个线程的返回值，是个很困难的问题，因此不能用Tread类或Runnable接口，我用的是Callable和ThreadPoolExecutor，Callable的process方法可以允许有返回值，ThreadPoolExecutor的invokeAll或submit方法可以拿到线程的执行结果

案例
假设需要给100个用户发送邮件，并需要每个用户的返回结果，先看下代码结构

CallableTemplate.java

package com.mairuan.base.concurrent;

import java.util.concurrent.Callable;

/**
 * 多线程模板类
 * 
 * @author Administrator
 *
 * @param 
 */
public abstract class CallableTemplate<V> implements Callable<V> {
    /**
     * 前置处理，子类可以Override该方法
     */
    public void beforeProcess() {
        System.out.println("before process....");
    }
    /**
     * 处理业务逻辑的方法,需要子类去Override
     * @return
     */
    public abstract V process();
    /**
     * 后置处理，子类可以Override该方法
     */
    public void afterProcess() {
        System.out.println("after process....");
    }
    @Override
    public V call() throws Exception {
        beforeProcess();
        V result = process();
        afterProcess();
        return result;
    }
}

CallableTemplate类实现了Callable接口，并实现了process方法，该类是一个抽象类，接收任意返回值的类型，beforeProcess方法为前置处理，afterProcess的后置处理，process为具体的业务逻辑抽象方法，该方法在子类中实现

IConcurrentThreadPool.java

package com.mairuan.base.concurrent;

import java.util.List;
import java.util.concurrent.ExecutionException;

public interface IConcurrentThreadPool {
    /**
     * 初始化线程池
     */
    void initConcurrentThreadPool();

    /**
     * 提交单个任务
     * 
     * @param task
     * @return
     */
     V submit(CallableTemplate task) throws InterruptedException,
            ExecutionException;

    /**
     * 提交多个任务
     * 
     * @param tasks
     * @return
     */
     List invokeAll(List> tasks)
            throws InterruptedException, ExecutionException;
}

IConcurrentThreadPool是多线程接口类，声名了三个方法，initConcurrentThreadPool:初始化线程池，submit：提交单个任务的线程，并有返回值，invokeAll：提交多个任务的线程，并有返回值

ConcurrentThreadPool.java

package com.mairuan.base.concurrent.impl;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

import com.mairuan.base.concurrent.CallableTemplate;
import com.mairuan.base.concurrent.IConcurrentThreadPool;

public class ConcurrentThreadPool implements IConcurrentThreadPool {
    private ThreadPoolExecutor threadPoolExecutor;
    // 核心线程数
    private int corePoolSize = 10;
    // 最大线程数
    private int maximumPoolSize = 20;
    // 超时时间30秒
    private long keepAliveTime = 30;

    @Override
    public void initConcurrentThreadPool() {
        threadPoolExecutor = new ThreadPoolExecutor(corePoolSize,
                maximumPoolSize, keepAliveTime, TimeUnit.SECONDS,
                new LinkedBlockingDeque());
    }

    @Override
    public  V submit(CallableTemplate task) throws InterruptedException,
            ExecutionException {
        Future result = threadPoolExecutor.submit(task);

        return result.get();
    }

    @Override
    public  List invokeAll(List> tasks)
            throws InterruptedException, ExecutionException {

        List> tasksResult = threadPoolExecutor.invokeAll(tasks);
        List resultList = new ArrayList();

        for (Future future : tasksResult) {
            resultList.add(future.get());
        }

        return resultList;
    }

}

ConcurrentThreadPool是创建线程池的实现类，用到了ThreadPoolExecutor线程池类及这个类的invokeAll方法和submit方法，这两个方法的返回值，都可以通过Future类的get方法获得

ICallableTaskFrameWork.java

public interface ICallableTaskFrameWork {
     List submitsAll(List extends CallableTemplate> tasks)
            throws InterruptedException, ExecutionException;
}

ICallableTaskFrameWork是定义的线程任务框架接口，所有的多线程调用，都通过该接口发起

CallableTaskFrameWork.java

package com.mairuan.base.concurrent.impl;

import java.util.List;
import java.util.concurrent.ExecutionException;

import com.mairuan.base.concurrent.CallableTemplate;
import com.mairuan.base.concurrent.ICallableTaskFrameWork;
import com.mairuan.base.concurrent.IConcurrentThreadPool;

public class CallableTaskFrameWork implements ICallableTaskFrameWork {

    private IConcurrentThreadPool concurrentThreadPool = new ConcurrentThreadPool();

    @Override
    public  List submitsAll(List> tasks)
            throws InterruptedException, ExecutionException {

        concurrentThreadPool.initConcurrentThreadPool();

        return concurrentThreadPool.invokeAll(tasks);
    }

}

CallableTaskFrameWork是ICallableTaskFrameWork 的实现类，在submitsAll实现方法中，通过调用线程池对象IConcurrentThreadPool接口的invokeAll方法来发起多线程的调用，这里注意一个，在submitAll实现方法中，我手动的调用了初始化线程池的方法concurrentThreadPool.initConcurrentThreadPool()，在真实的项目上，应该在应用启动的时候就调用该方法来初始化线程池

测试类代码
SendMessageService.java，假设这是一个发送邮件信息的服务类

package com.mairuan.base.concurrent.test;

public class SendMessageService {
    public void sendMessage(String email,String content){
        System.out.println("发送邮件。。。");
    }
}

SendMessageHander.java，多线程发送邮件的处理类

package com.mairuan.base.concurrent.test;

import java.util.HashMap;
import java.util.Map;

import com.mairuan.base.concurrent.CallableTemplate;

public class SendMessageHander extends CallableTemplate<Map<String, String>> {

    private String email;
    private String content;
    public SendMessageHander(String email,String content) {
        this.email = email;
        this.content = content;
    }

    @Override
    public Map<String, String> process() {
        SendMessageService sendMessageService = new SendMessageService();
        sendMessageService.sendMessage(email, content);
        Map<String, String> map = new HashMap<String, String>();
        map.put(email, content);
        return map;
    }

}

这个类继承了上面的CallableTemplate，我们要的返回值是Map，因此泛型类型是Map，在类中还重写了process方法，在方法中调用发送邮件的业务逻辑接口SendMessageService.sendMessage，并将返回结果组装成Map返回，这里我就简单处理了，将邮件地址及内容放在Map中直接返回了；另外还要注意这个类有个有参构造器，通过构建器可以接收需要传递进来的参数

SendMessageTest.java，测试类

package com.mairuan.base.concurrent.test;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ExecutionException;

import com.mairuan.base.concurrent.CallableTemplate;
import com.mairuan.base.concurrent.ICallableTaskFrameWork;
import com.mairuan.base.concurrent.impl.CallableTaskFrameWork;

public class SendMessageTest {
    public static void main(String[] args) throws InterruptedException,
            ExecutionException {
        ICallableTaskFrameWork callableTaskFrameWork = new CallableTaskFrameWork();
        List>> tasks = new ArrayList>>();
        SendMessageHander sendMessageHander = null;
        // 将需要发送邮件的邮件地址及内容组装好，放在一个集合中
        for (int i = 0; i < 1000; i++) {
            sendMessageHander = new SendMessageHander("email" + i, "content"
                    + i);

            tasks.add(sendMessageHander);
        }
        //通过多线程一次性发起邮件，并拿到返回结果集
        List> results = callableTaskFrameWork
                .submitsAll(tasks);
        // 解析返回结果集
        for (Map map : results) {
            for (Entry entry : map.entrySet()) {
                System.out.println(entry.getKey() + "\t" + entry.getValue());
            }
        }

    }
}

运行结果