IO创建Socket通信中慎用BufferReader中的readLine()

Posted 2020-11-03 lonecloud

在编写Socket的Demo的时候，在Server中使用BufferReader获取从客服端发送过来的内容

package cn.lonecloud.socket;

import cn.lonecloud.thread.factory.TraceThreadPool;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.time.Instant;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

/**
 * @author lonecloud
 * @version v1.0
 * @date 下午5:11 2018/5/9
 */
public class SocketServer {
     //创建线程
    static ExecutorService service = new ThreadPoolExecutor(0, 10, 60L, TimeUnit.SECONDS, new SynchronousQueue<>());
   //处理消息类
    static class HandlerMsg implements Runnable {
        //客户端socket
        Socket clientSocket;

        public HandlerMsg(Socket clientSocket) {
            this.clientSocket = clientSocket;
        }

        @Override
        public void run() {
            BufferedReader reader = null;
            PrintWriter pr = null;
            try {
               //获取消息
                reader = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                pr = new PrintWriter(clientSocket.getOutputStream(), true);
                Instant now = Instant.now();
                String s = null;
                while ((s = reader.readLine()) != null) {
                    pr.append(s);
                }
                pr.close();
                reader.close();
                clientSocket.close();
                System.out.println("spend "+(Instant.now().getNano()-now.getNano()));
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

　　client

 

package cn.lonecloud.socket;

import java.io.*;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.util.Scanner;

/**
 * @author lonecloud
 * @version v1.0
 * @date 下午5:24 2018/5/9
 */
public class SocketClient {

    public static void main(String[] args) throws IOException {
        Socket socket=new Socket();
　　　　　//链接
        socket.connect(new InetSocketAddress("localhost",8000));
        PrintWriter printWriter = new PrintWriter(socket.getOutputStream(),true);
        //获取输入
　　　　　Scanner scanner=new Scanner(System.in);
        String s = scanner.nextLine();
        //必须使用println不然会一直卡在这里
　　　　  printWriter.println(s);
        printWriter.flush();
　　　　　//读取数据
        InputStream inputStream = socket.getInputStream();
        BufferedReader reader=new BufferedReader(new InputStreamReader(inputStream));
        //打印
　　　　  System.out.println("from server"+reader.readLine());
        System.out.flush();
        printWriter.close();
        reader.close();
        socket.close();

    }
}

　　Main

package cn.lonecloud.socket;

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

/**
 * @author lonecloud
 * @version v1.0
 * @date 下午5:21 2018/5/9
 */
public class ServerMain {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = null;
        Socket clientSocket = null;
        serverSocket = new ServerSocket(8000);
        while (true) {
            clientSocket = serverSocket.accept();
            System.out.println(clientSocket.getRemoteSocketAddress() + "connect");
            SocketServer.service.execute(new SocketServer.HandlerMsg(clientSocket));
        }
    }
}

　　出现如下问题，如果Socket中如果对采用如下代码

while ((s = reader.readLine()) != null) {
                    pr.append(s);
                }

　　如果其在客户端不采用println打印换行符，将导致客户端与服务器端一直处于工作状态，因为其一直都未接收到"\n"