Question

我正在尝试使用在2个线程之间进行通信的管道创建一个程序（你可以说两个线程之间的聊天），我的问题在于你写的时候没有问题，但是当我通过管道读取消息时得到一个无限的块，我找不到合适的解决方案，所以发送的所有消息＆amp;收到的信息显示在控制台中所以我试图从线程1发送消息到线程2并且它工作，但是从线程2到1，有一个块。

我的程序由3个类组成，我将在下面显示：

package pipes1;

public class Main 
{
public static void main(String[] args) throws Throwable
{
    Pipe p1 = new Pipe();
    Pipe p2 = new Pipe();
    Person alice = new Person("Alice",p1,"recieved, thanks","hi bob");
    Person bob = new Person("Bob",p2,"hi alice","recieved, thanks");

    Thread terminal1 = new Thread(new Runnable()
    {
        @Override
        public void run() 
        {
            try 
            {
                bob.connection(alice);
                bob.send(bob.getName()+":"+bob.getMsg1());
                bob.recieve(alice.getName()+":"+alice.getMsg1());
                bob.recieve(alice.getName()+":"+alice.getMsg2());
                bob.send(bob.getName()+":"+bob.getMsg2());
                bob.send("1 to 2\n");
                bob.recieve();
                bob.recieve();
                bob.send("ack 1\n");
                bob.closing();
            } 
            catch (Throwable e) 
            {
                System.out.println(e.getMessage());
                e.printStackTrace();
            }
        }
    });

    //terminal of a
    Thread terminal2 = new Thread(new Runnable()
    {
        @Override
        public void run() 
        {
            try 
            {
                alice.connection(bob);
                alice.recieve(bob.getName()+":"+bob.getMsg1());
                alice.send(alice.getName()+":"+alice.getMsg1());
                alice.send(alice.getName()+":"+alice.getMsg2());
                alice.recieve(bob.getName()+":"+bob.getMsg2());
                alice.recieve();
                alice.send("2 to 1\n");
                alice.send("ack 2\n");
                alice.recieve();
                alice.closing();
            } 
            catch (Throwable e) 
            {
                System.out.println(e.getMessage());
                e.printStackTrace();
            }
        }
    });
    terminal1.start();
    terminal2.start();
}
}

=============================================== ==========================

package pipes1;

import java.io.IOException;

public class Person 
{
private String name; //name of person
private String msg1;
private String msg2;
private Pipe pipe;

public String getMsg1() 
{
    return msg1;
}

public String getMsg2() 
{
    return msg2;
}

public Pipe getPipe() 
{
    return pipe;
}

public String getName() 
{
    return name;
}

public Person(String name,Pipe pipe,String s1,String s2)
{
    this.name = name;
    this.msg1 = s1;
    this.msg2 = s2;
    this.pipe = pipe;
}

public void connection(Person x) throws Throwable
{
    pipe.getReader().connect(x.pipe.getWriter());
}

public void closing() throws IOException
{
    this.pipe.getReader().close();
    this.pipe.getWriter().close();
}

public void send(String m) throws IOException
{
    this.pipe.getWriter().write(m);
    this.pipe.getWriter().flush();
}

public void recieve() throws IOException
{

                int data = this.pipe.getReader().read();
                while(data!=-1)
                {
                            System.out.print((char)data);
                            data = this.pipe.getReader().read();
                }
                System.out.println("");             
}

public void recieve(String m) throws IOException
{
    int i = 0;
    while(i<m.length())
    {
            System.out.print((char) this.pipe.getReader().read());
            i++;
    }
    System.out.println("");
}
}

=============================================== ==========================

package pipes1;
import java.io.*;

public class Pipe 
{
private PipedWriter writer;
private PipedReader reader;

public PipedWriter getWriter() 
{
    return writer;
}

public PipedReader getReader() 
{
    return reader;
}

public Pipe()
{
    writer = new PipedWriter();
    reader = new PipedReader();
}
}

=============================================== ======

并且控制台的结果总是像这样

Bob:hi alice

Alice:recieved, thanks

Alice:hi bob

Bob:recieved, thanks

1 to 2

// here comes the block , thread 1 can't get the message "2 to 1"

Answer 1

从管道读取是阻塞的，因为它尚未关闭。这可能会奏效：

public void receive() throws IOException {

    while(this.pipe.getReader().ready()) {
        int data = this.pipe.getReader().read();
        System.out.print((char) data);
    }
    System.out.println();
}

更新：我错了，这就足够了。比较.read() == -1仅用于测试管道的另一侧是否关闭，以及管道上的最后一个字符是否已收到。测试.ready()是当时管道上是否有任何字符。因为发送和接收是在两个线程上，准备就绪是不确定的，如果你没准备就停止阅读，你可能会得到一个部分线。

考虑到这一点，您需要一个不同的测试。我会用终结符令牌（例如0）附加每条消息，然后在另一端附加。所以这是我已经测试过的解决方案：

public void send(String m) throws IOException {
    this.pipe.getWriter().write(m);
    this.pipe.getWriter().write(0);
    this.pipe.getWriter().flush();
}

public void receive() throws IOException {
    while(true) {
        int data = this.pipe.getReader().read();
        if (data == 0) break;
        System.out.print((char) data);
    }
    System.out.println();
}

public void receive(String m) throws IOException {
    for (int i = 0; i < m.length(); i++) {
        System.out.print((char) this.pipe.getReader().read());
    }
    this.pipe.getReader().read(); // consume the terminator
    System.out.println();
}

Java管道，为什么我在从管道读取时无限期地被阻塞

1 个答案: