package com.dubbo.analyzer.executor;

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

/**
 * 任务执行者<br/>
 * 当线程不够且线程队列爆满时,会租塞生产者<br/>
 * 此类为单例,必须先调用 init 方法进行初始化.<br/>
 * <a href="http://www.importnew.com/10790.html" target="_blank">http://www.importnew.com/10790.html</a>
 * @author BennyTian
 * @date 2015/01/06
 */
public class Executor {
	
	private Executor() { }

	private static ThreadPoolExecutor executor = null;
	
	private static TimeUnit unit = TimeUnit.MINUTES ;
	private static long keepAliveTime = 1;
	
	/**
	 * 初始化
	 * @param threadSize	线程数
	 * @param poolSize		线程租塞队列的容量
	 */
	public static void init(Integer threadSize,Integer poolSize){
		executor = new ThreadPoolExecutor(threadSize, threadSize, keepAliveTime, unit, new ArrayBlockingQueue<Runnable>(threadSize));
		//异常捕获处理:当线程池达到处理最大极限的时候,调用 queue.put 对生产者进行租塞. execute方法默认使用的是异步的 queue.offer
		executor.setRejectedExecutionHandler(new RejectedExecutionHandler() {
			@Override
			public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
				try {
					executor.getQueue().put(r);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}
		});
	}
	
	/**
	 * 执行任务
	 * @param task
	 */
	public static void execute(Runnable task){
		verify();
		executor.execute(task);
	}
	
	/**
	 * 线程池的任务是否全部执行完成
	 * @return
	 */
	public static Boolean isCompleted(){
		return executor.getActiveCount() == 0;
	}
	
	/**
	 * 停止任务
	 */
	public static void shutdown(){
		verify();
		executor.shutdown();
	}
	
	private static void verify(){
		if(executor==null){
			throw new RuntimeException("please invoke [ init ] method");
		}
	}
	
}