怎么利用JAVA實(shí)現(xiàn)可以自行關(guān)閉服務(wù)器

發(fā)布時間：2021-06-30 09:24:46 來源：億速云閱讀：99 作者：小新欄目：開發(fā)技術(shù)

這篇文章將為大家詳細(xì)講解有關(guān)怎么利用JAVA實(shí)現(xiàn)可以自行關(guān)閉服務(wù)器，小編覺得挺實(shí)用的，因此分享給大家做個參考，希望大家閱讀完這篇文章后可以有所收獲。

JAVA實(shí)現(xiàn)可以自行關(guān)閉的服務(wù)器

普通實(shí)現(xiàn)的服務(wù)器都無法關(guān)閉自身，只有依靠操作系統(tǒng)來強(qiáng)行終止服務(wù)程序。這種強(qiáng)行終止服務(wù)程序的方式盡管簡單方便，但會導(dǎo)致服務(wù)器中正在執(zhí)行的任務(wù)突然中斷。如果服務(wù)器處理的任務(wù)非常重要，不允許被突然中斷，應(yīng)該由服務(wù)器自身在恰當(dāng)?shù)臅r刻關(guān)閉自己

代碼如下：

EchoServer類

package ShutdownServer;

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
import java.net.SocketTimeoutException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.TimeUnit;

public class EchoServer {
    private int port=8000;
    private ServerSocket serverSocket;
    private ExecutorService executorService; //線程池
    private final int POOL_SIZE=4; //單個CPU時線程池中工作線程的數(shù)目

    private int portForShutdown=8001; //用于監(jiān)聽關(guān)閉服務(wù)器命令的端口
    private ServerSocket serverSocketShutdown;
    private boolean isShutdown=false; //服務(wù)器是否已經(jīng)關(guān)閉

    private Thread shutdownThread=new Thread(){
        //負(fù)責(zé)關(guān)閉服務(wù)器的線程
        public void run(){
            while(!isShutdown){
                Socket socketForShutdown=null;
                try{
                    socketForShutdown=serverSocketShutdown.accept();
                    BufferedReader br=new BufferedReader(
                            new InputStreamReader(socketForShutdown.getInputStream())
                    );
                    String command=br.readLine();
                    if (command.equals("shutdown")){
                        long beginTime=System.currentTimeMillis();
                        socketForShutdown.getOutputStream().write("服務(wù)器正在關(guān)閉\r\n".getBytes());
                        isShutdown=true;

                        //請求關(guān)閉線程池
                        //線程池不再接收新的任務(wù)，但會繼續(xù)執(zhí)行完工作隊(duì)列中現(xiàn)有的任務(wù)
                        executorService.shutdown();

                        //等待關(guān)閉線程池，每次等待的超時時間為30s
                        //當(dāng)使用awaitTermination時，主線程會處于一種等待的狀態(tài)，等待線程池中所有的線程都運(yùn)行完畢后才繼續(xù)運(yùn)行。
                        //如果等待的時間超過指定的時間，但是線程池中的線程運(yùn)行完畢，那么awaitTermination()返回true。執(zhí)行分線程已結(jié)束
                        //如果等待的時間超過指定的時間，但是線程池中的線程未運(yùn)行完畢，那么awaitTermination()返回false。不執(zhí)行分線程已結(jié)束
                        //如果等待時間沒有超過指定時間，等待！
                        //可以用awaitTermination()方法來判斷線程池中是否有繼續(xù)運(yùn)行的線程。
                        while(!executorService.isTerminated())
                            executorService.awaitTermination(30, TimeUnit.SECONDS);
                            //關(guān)閉與EchoClient客戶通信的ServerSocket
                            serverSocket.close();
                            long endTime=System.currentTimeMillis();
                            socketForShutdown.getOutputStream().write(("服務(wù)器關(guān)閉，"+"關(guān)閉服務(wù)器用了"+(endTime-beginTime)+"ms\r\n").getBytes());
                            socketForShutdown.close();
                            serverSocketShutdown.close();
                            System.out.println("服務(wù)器關(guān)閉");
                    }
                    else {
                        socketForShutdown.getOutputStream().write("錯誤的命令\r\n".getBytes());
                        socketForShutdown.close();
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    };

    public EchoServer() throws IOException {
        serverSocket=new ServerSocket(port);
        //設(shè)定等待客戶連接的超時時間為60s
        serverSocket.setSoTimeout(60000);
        serverSocketShutdown=new ServerSocket(portForShutdown);

        //創(chuàng)建線程池
        executorService= Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors() * POOL_SIZE);
        shutdownThread.start();
        System.out.println("服務(wù)器啟動");
    }

    public void service(){
        while(!isShutdown){
            Socket socket=null;
            try {
                //可能會拋出SocketTimeoutException和SocketException
                socket=serverSocket.accept();
                //把等待客戶發(fā)送數(shù)據(jù)的超時時間設(shè)為60s
                socket.setSoTimeout(60000);
                //可能會拋出RejectedExecutionException
                executorService.execute(new Handler(socket));
            }catch (SocketTimeoutException e){
                //不必處理等待客戶連接時出現(xiàn)的異常
            }catch (RejectedExecutionException e) {
                try {
                    if (socket != null)
                        socket.close();
                } catch (IOException ex) {
                    return;
                }
            }catch (SocketException e){
                if (e.getMessage().indexOf("socket closed")!=-1)
                    return;
            }catch (IOException e){
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) throws IOException { //main方法拋出異常，異常直接交給虛擬機(jī)，虛擬機(jī)直接結(jié)束異常
        new EchoServer().service();
    }
}

//負(fù)責(zé)與單個客戶通信的任務(wù)
class Handler implements Runnable{
    private Socket socket;
    public Handler(Socket socket){
        this.socket=socket;
    }

    private PrintWriter getWriter(Socket socket) throws IOException{
        OutputStream socketOut=socket.getOutputStream();
        return new PrintWriter(socketOut,true);
    }
    private BufferedReader getReader(Socket socket) throws IOException{
        InputStream socketIn=socket.getInputStream();
        return new BufferedReader(new InputStreamReader(socketIn));
    }
    public String echo(String msg){
        return "echo: "+msg;
    }

    @Override
    public void run() {
        try{
            System.out.println("New connection accepted "+socket.getInetAddress()+":"+socket.getPort());
            BufferedReader br=getReader(socket);
            PrintWriter pw=getWriter(socket);

            String msg=null;
            //接收和發(fā)送數(shù)據(jù)，直到通信結(jié)束
            while((msg=br.readLine())!=null){
                System.out.println("from "+socket.getInetAddress()+":"+socket.getPort()+">"+msg);
                pw.println(echo(msg));
                if (msg.equals("bye"))
                    break;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            try{
                if (socket!=null)
                    socket.close();
            }catch (IOException e){
                e.printStackTrace();
            }
        }
    }
}

AdminClient類（負(fù)責(zé)向EchoServer發(fā)送“shutdown”命令，關(guān)閉服務(wù)器）

package ShutdownServer;

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

public class AdminClient {
    public static void main(String[] args){
        Socket socket=null;
        try{
            socket=new Socket("localhost",8001);
            //發(fā)送關(guān)閉命令
            OutputStream socketOut=socket.getOutputStream();
            //Scanner scanner=new Scanner(System.in);
            //String order=scanner.next();
            socketOut.write("shutdown\r\n".getBytes());
            //接收服務(wù)器反饋
            BufferedReader br=new BufferedReader(new InputStreamReader(socket.getInputStream()));
            String msg=null;
            while ((msg=br.readLine())!=null){
                System.out.println(msg);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            try{
                if (socket!=null)
                    socket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

Client類（客戶，與服務(wù)器進(jìn)行通訊）

package ShutdownServer;

import java.io.*;
import java.net.Socket;

public class Client {
    private String host="localhost";
    private int port=8000;
    private Socket socket;

    public Client() throws IOException {
        socket=new Socket(host,port);
    }

    private PrintWriter getWriter(Socket socket) throws IOException{
        OutputStream socketOut=socket.getOutputStream();
        return new PrintWriter(socketOut,true);
    }

    private BufferedReader getReader(Socket socket) throws IOException{
        InputStream socketIn=socket.getInputStream();
        return new BufferedReader(new InputStreamReader(socketIn));
    }

    public void talk() throws IOException{
        try{
            BufferedReader br=getReader(socket);
            PrintWriter pw=getWriter(socket);
            BufferedReader localReader=new BufferedReader(new InputStreamReader(System.in));
            String msg=null;
            while((msg=localReader.readLine()) != null){
                pw.println(msg);
                System.out.println(br.readLine());

                if (msg.equals("bye")){
                    break;
                }
            }
        }catch (IOException e){
            e.printStackTrace();
        }
        finally {
            try{
                socket.close();
            }catch (IOException e){
                e.printStackTrace();
            }
        }
    }

    public static void main(String args[]) throws IOException {
        new Client().talk();
    }
}

shutdownThread線程負(fù)責(zé)關(guān)閉服務(wù)器，它一直監(jiān)聽8001端口，如果接收到了AdminClient發(fā)送的“shutdown”命令，就把isShutdown設(shè)置為true。

在關(guān)閉服務(wù)器時，我們使用了最常用的方法，先調(diào)用線程池的shutdown()方法，接著調(diào)用線程池的awaitTermination()方法。

executorService.shutdown();

                        //等待關(guān)閉線程池，每次等待的超時時間為30s
                        //當(dāng)使用awaitTermination時，主線程會處于一種等待的狀態(tài)，等待線程池中所有的線程都運(yùn)行完畢后才繼續(xù)運(yùn)行。
                        //如果等待的時間超過指定的時間，但是線程池中的線程運(yùn)行完畢，那么awaitTermination()返回true。執(zhí)行分線程已結(jié)束
                        //如果等待的時間超過指定的時間，但是線程池中的線程未運(yùn)行完畢，那么awaitTermination()返回false。不執(zhí)行分線程已結(jié)束
                        //如果等待時間沒有超過指定時間，等待！
                        //可以用awaitTermination()方法來判斷線程池中是否有繼續(xù)運(yùn)行的線程。
                        while(!executorService.isTerminated())
                            executorService.awaitTermination(30, TimeUnit.SECONDS);

在線程池執(zhí)行了shutdown()方法后，線程池不會在接收新的任務(wù)，同時該線程因?yàn)檎{(diào)用awaitTermination()方法而發(fā)生阻塞，直到線程池中所有線程的任務(wù)執(zhí)行完畢，該線程才會繼續(xù)向下