问创建一个java服务器套接字，该套接字使用线程池等待来自客户端的消息
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Stack Overflow用户

提问于 2020-03-25 14:06:29

回答 1查看 43关注 0票数 0

@FXML
private TextArea textarea;
@FXML
private ImageView imagev;

@Override
public void initialize(URL url, ResourceBundle resourceBundle) {
    Serverth Server = new Serverth();
    Server.start();
}


class Serverth extends Thread {
    @Override
    public void run() {
        try {
            final int NUM_THREAD = 99;


            ServerSocket socket = new ServerSocket(8078);
            ExecutorService exec = Executors.newFixedThreadPool(NUM_THREAD);
            System.out.println("SERVER SOCKET CREATED");


            while (!isInterrupted()) {
                Socket in = socket.accept();
                Runnable r = new ThreadedHandler(in);
                exec.execute(r);

            }
        } catch (IOException e) {
            System.out.println(e.getMessage());
        }

    }
}

class ThreadedHandler implements Runnable {

    private Socket incoming;

    public ThreadedHandler(Socket in) {
        incoming = in;
    }

    public void run() {
        try {
            try {
                ObjectInputStream is=new ObjectInputStream(incoming.getInputStream());

                while(true) {
                    if (is.available() > 0) {
                        String line = is.readUTF();

                        textarea.appendText("\n" + "[" + new java.util.Date() + "] : " + line);

                        if (line.contains("inviato")) {
                            Object obj = is.readObject();
                            Email ema = (Email) obj;
                            try {
                                SimpleDateFormat formatter = new SimpleDateFormat("dd-M-yyyy-hh-mm-ss");
                                FileOutputStream fileOut = new FileOutputStream("src/Server/" + ((Email) obj).getDestinat() + "/" +  formatter.format(((Email) obj).getData()) + ".txt");
                                ObjectOutputStream objectOut = new ObjectOutputStream(fileOut);
                                objectOut.writeObject(ema);
                                objectOut.flush();
                                objectOut.close();
                                System.out.println("The Object  was succesfully written to a file");

                            } catch (Exception ex) {
                                ex.printStackTrace();
                            }

                        }

                    }
                }
                } catch(IOException ex) {
                ex.printStackTrace();
            }

        } catch (ClassNotFoundException e) {
                e.printStackTrace();
            } finally {
            try {
                incoming.close();
            } catch (IOException ex) {
                ex.printStackTrace();
            }

        }
    }
}

在run方法(在Serveth类中)中，我创建了一个服务器套接字并调用exec.execute方法。在run方法中(在ThreadedHandler类中)，服务器正在等待来自客户机的消息(在本例中，它创建了一个新的.txt文件，但这并不重要)。一切正常，但会导致CPU的过度使用和延迟！

sockets

message

runnable

java

multithreading

回答 1

Stack Overflow用户

回答已采纳

发布于 2020-03-25 15:28:34

InputSteam.available方法立即返回一个值，告诉您没有字节可供读取，因此此代码运行一个非常“热”的自旋循环：

            while(true) {
                if (is.available() > 0) {
                    ...
                }
            }

available方法很少有用，而且经常会给出令人困惑的结果(例如，请参阅inputstream.available() is 0 always)。我建议你完全去掉if语句：

            while(true) {
                String line = is.readUTF();

                textarea.appendText("\n" + "[" + new java.util.Date() + "] : " + line);
                ...
            }