java Socket简单聊天实现 —— 使用线程池及同步锁

现有的聊天室功能虽然已经完成，但是由于客户端的频繁连接与断开，会使得服务端频繁的创建及销毁线程。随着客户端的增加，服务端的线程也在增加，这无疑会对服务端的资源造成浪费，并且由于过多的线程导致的过度切换也会为服务端带来崩溃的风险。与此同时，多个线程会共享服务端的集合属性allOut，这里还存在着多线程并发的安全问题。

为此，需要重构聊天室案例，使用线程池技术来解决服务端多线程问题，并解决多线程并发的安全问题。

服务器端：需要在服务器端定义一个线程池类型的属性，用于管理服务端的线程创建及管理。修改Server的start方法，将原来创建并启动线程的代码替换为使用线程池管理的方式。然后在Server中添加三个方法，用于操作属性allOut，并使用同步锁，使三个方法变为同步的。

package TCPUDP;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class Server {

private ServerSocket serverSocket;
//所有客户端输出流
private List<PrintWriter> allOut;
//线程池
private ExecutorService threadPool;

public Server(){
try{
serverSocket = new ServerSocket(8088);
allOut = new ArrayList<PrintWriter>();
threadPool = Executors.newFixedThreadPool(40);
}catch(Exception e){
e.printStackTrace();
}
}

/*
* 将输出流存入共享集合，与下面两个方法互斥，保证同步安全
*/
private synchronized void addOut(PrintWriter out){
allOut.add(out);
}
private synchronized void removeOut(PrintWriter out){
allOut.remove(out);
}
private synchronized void sendMessage(String message){
for(PrintWriter o:allOut){
o.println(message);
}
}

/*
* 线程体：用于并发处理不同客户端的交互
*
*/
class ClientHandler implements Runnable{

private Socket socket;

//构造函数设置为public
public ClientHandler(Socket socket){
this.socket = socket;
}

@Override
public void run() {
PrintWriter pw = null;
try {
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os, "UTF-8");
pw = new PrintWriter(osw, true);
//存入共享集合
//allOut.add(pw);
addOut(pw);

InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is, "UTF-8");
BufferedReader br = new BufferedReader(isr);
String message = null;
while((message = br.readLine()) != null){
//for(PrintWriter o: allOut){
//    o.println(message);
sendMessage(message);
}
}catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
//当客户端断线时，要将输出流从集合中删除
//allOut.remove(pw);
removeOut(pw);
if(socket != null){
try{
socket.close();
}catch(Exception e){
e.printStackTrace();
}
}
}
}
}

public void start(){
try{
//循环监听客户端的连接
while(true){

System.out.println("等待客户端连接。。。");
Socket socket = serverSocket.accept();
System.out.println("客户端已连接！");

ClientHandler handler = new ClientHandler(socket);
//启动一个线程来完成针对该客户端的交互
threadPool.execute(handler);
}
}catch(Exception e){
e.printStackTrace();
}
}

public static void main(String[] args) {
// TODO Auto-generated method stub
Server server = new Server();
server.start();
}

}

客户端：

package TCPUDP;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Scanner;

public class Client {

private Socket socket;

public Client(){
try {
socket = new Socket("localhost", 8088);
} catch (Exception e) {
e.printStackTrace();
}
}

private class ServerHandler implements Runnable{

@Override
public void run() {
// TODO Auto-generated method stub
try{
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is, "UTF-8");
BufferedReader br = new BufferedReader(isr);
while(true){
System.out.println(br.readLine());
}
}catch(Exception e){
e.printStackTrace();
}
}
}

public void start(){

try{
ServerHandler handler = new ServerHandler();
Thread t = new Thread(handler);
t.setDaemon(true);
t.start();

OutputStream out = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(out, "UTF-8");
PrintWriter pw = new PrintWriter(osw, true);
//创建Scanner读取用户输入内容
Scanner scanner = new Scanner(System.in);
while(true){
pw.println(scanner.nextLine());
}
}catch(Exception e){
e.printStackTrace();
}finally{
if(socket != null){
try{
socket.close();
}catch(Exception e){
e.printStackTrace();
}
}
}
}

public static void main(String[] args) {
// TODO Auto-generated method stub
Client client = new Client();
client.start();
}

}