java同步阻塞IO

最新推荐文章于 2024-07-24 10:04:54 发布

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本文通过一个Java实现的时间服务器示例介绍了传统的同步阻塞IO模型。该模型中，每当客户端发起连接请求，服务器都会为该连接创建一个新的线程进行处理。然而，这种做法在面对高并发场景时存在明显不足。

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server端：

package yunsheng;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

public class TimeServer {

    /**
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) throws IOException {
        int port = 8080;
        if (args != null && args.length > 0) {
            try {
                port = Integer.valueOf(args[0]);
            } catch (NumberFormatException 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;
            while (true) {
                socket = server.accept(); // 接收客户端连接请求，没有的时候就阻塞
                System.out.println("accept");
                new Thread(new TimeServerHandler(socket)).start();
            }
        } finally {
            if (server != null) {
                System.out.println("The time server close");
                server.close();
                server = null;
            }
        }
    }
}

handler处理：

package yunsheng;

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

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(); // 从客户端读
                if (body == null)
                    break;
                System.out.println("The time server receive order: " + body);
                currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body) ? new java.util.Date(System.currentTimeMillis())
                        .toString() : "BAD ORDER";
                System.out.println(currentTime);
                out.println(currentTime);

            }
        } catch (Exception e) {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
            }
            if (out != null) {
                out.close();
                out = null;
            }
            if (this.socket != null) {
                try {
                    this.socket.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
                this.socket = null;
            }
        }
    }
}

客户端：

package yunsheng;

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


public class TimeClient {
    public static void main(String[] args) {
        int port = 8080;
        if(args != null && args.length > 0){
            try {
                port = Integer.valueOf(args[0]);
            } catch (NumberFormatException e) {
                //采用默认值
            }
        }
        Socket socket = null;
        BufferedReader in = null;
        PrintWriter out = null;
        try {
            socket = new Socket("127.0.0.1",port);    //创建socket
            in = new BufferedReader(new InputStreamReader(socket.getInputStream())); 
            out = new PrintWriter(socket.getOutputStream(),true);
            out.println("QUERY TIME ORDER"); //向服务端写出QUERY TIME ORDER
            System.out.println("Send order 2 server succeed.");
            String resp = in.readLine();
            System.out.println("Now is : " +  resp);
        } catch (Exception e) {
            //不需要处理
        } finally {
            if(out != null ){
                out.close();
                out = null;
            }
            if(in != null){
                try {
                    in.close();
                } catch (IOException e2) {
                    e2.printStackTrace();
                }
                in = null;
            }
            if(socket != null){
                try {
                    socket.close(); 
                } catch (IOException e3) {
                    e3.printStackTrace();
                }
                socket = null;
            }
        }
    }
}