Java IO编程全解（三）——伪异步IO编程

package joanna.yan.poio;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
/**
 * 伪异步式I/O
 * @author Joanna.Yan
 * @date 2017年10月24日上午10:16:10
 */
public class TimeServer {

    public static void main(String[] args) {
        int port=9090;
        if(args!=null&&args.length>0){
            try {
                port=Integer.valueOf(args[0]);
            } catch (Exception e) {
                // 采用默认值
            }
        }
        
        ServerSocket server=null;
        try {
            server=new ServerSocket(port);
            System.out.println("The time server is start in port :"+ port);
            Socket socket=null;
            //创建一个时间服务器类的线程池
            TimeServerHandlerExecutePool singleExecutor=new 
                    TimeServerHandlerExecutePool(50, 10000);//创建I/O任务
            
            while(true){
                socket=server.accept();
                //当接收到新的客户端连接时，将请求Socket封装成一个Task，然后调用execute方法执行。从而避免了每个请求接入都创建一个新的线程。
                singleExecutor.execute(new TimeServerHandler(socket));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            if(server!=null){
                try {
                    System.out.println("The time server close");
                    server=null;
                    server.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

package joanna.yan.poio;

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
/**
 * 由于线程池和消息队列都是有界的，因此，无论客户端并发连接数多大，它都不会导致线程个数过于膨胀或者内存溢出，
 * 相比于传统的一连接一线程模型，是一种改良。
 * @author Joanna.Yan
 * @date 2017年10月24日下午2:39:49
 */
public class TimeServerHandlerExecutePool {
    private ExecutorService executor;
    
    public TimeServerHandlerExecutePool(int maxPoolSize,int queueSize){
        executor=new ThreadPoolExecutor(Runtime.getRuntime().availableProcessors(), 
                maxPoolSize, 120L, TimeUnit.SECONDS,
                new ArrayBlockingQueue<java.lang.Runnable>(queueSize));
        
    }
    
    public void execute(java.lang.Runnable task){
        executor.execute(task);;
    }
}

package joanna.yan.poio;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Date;

public class TimeServerHandler implements Runnable{
    private Socket socket;
    
    public TimeServerHandler(Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        BufferedReader in=null;
        PrintWriter out=null;
        
        try {
            in=new BufferedReader(new InputStreamReader(this.socket.getInputStream()));
            out=new PrintWriter(this.socket.getOutputStream(), true);
            String currentTime=null;
            String body=null;
            while(true){
                body=in.readLine();
                if(body==null){
                    break;
                }
                System.out.println("The time server receive order:"+body);
                //如果请求消息为查询时间的指令"QUERY TIME ORDER"则获取当前最新的系统时间。
                currentTime="QUERY TIME ORDER".equalsIgnoreCase(body) ? 
                        new Date(System.currentTimeMillis()).toString() : "BAD ORDER";
                out.println(currentTime);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            if(in!=null){
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(out!=null){
                out.close();
                out=null;
            }
            if(this.socket!=null){
                try {
                    this.socket.close();
                    this.socket=null;
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}