Question

我将以下代码作为OSGi模块。

运行时，我收到记录器已设置的消息：

UdpListener > setStoreLog: 'com.mine.logger.internal.storeindb.StoreLog@1c6f579'

但在此之后，run（）函数中的循环表明storeLog为空

ERROR > UdpListener > run > storeLog is not available.

任何想法可能出错？

这可能是一个在线程中运行的事实吗？

package com.mine.logger.internal.udp;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.util.Date;

import com.mine.logger.storeindb.IStoreLog;

public class UdpListener extends Thread
{
    private int port;

    private IStoreLog storeLog;

    public void setStoreLog(IStoreLog value)
    {
        this.storeLog = value;
        System.out.println("UdpListener > setStoreLog: '" + this.storeLog.toString() + "'");
    }

    public void unsetStoreLog(IStoreLog value)
    {
        if (this.storeLog == value) {
            this.storeLog = null;
        }
        System.out.println("UdpListener > unsetStoreLog");
    }

    public UdpListener() 
    {
        // public, no-args constructor needed for Declarative Services !!!
    }

    public UdpListener(int port) 
    {
        this.port = port;
    }

    public void run()
    {
        startListener();
    }

    private void startListener()
    {
        try {
            // send command
            DatagramSocket socket = new DatagramSocket(port);

            while (true)
            {
                byte[] b = new byte[1000];
                DatagramPacket recvdPacket = new DatagramPacket(b, b.length);
                socket.receive(recvdPacket);

                System.out.println("UdpListener: Packet received. " + (new String(b)));

                try
                {
                    if (this.storeLog != null)
                        this.storeLog.doStore(new Date(), InetAddress.getByName("0.0.0.0"), port, 1, "UDP", b);
                    else
                        System.err.println("ERROR > UdpListener > run > storeLog is not available.");
                }
                catch (Exception e)
                {
                    System.err.println("ERROR > UdpListener > run > storeLog > Exception: " + e.toString());
                }
            }
        } catch (SocketException e) {
            System.out.println("ERROR > UdpListener > run > SocketException: " + e.getMessage());
        } catch (IOException e) {
            System.out.println("ERROR > UdpListener > run > IOException: " + e.getMessage());
        } catch (Exception e) {
            System.out.println("ERROR > UdpListener > run > Exception: " + e.getMessage());
        }
    }
}

Answer 1

您的代码不是线程安全的。 storeLog字段由多个线程读取和写入，没有任何同步。如果您有一个可由多个线程读取和写入的可变字段，则必须确保始终安全地访问该字段读取和写入。我高度为任何编写Java代码的人推荐优秀的Java Concurrency in Practice http://www.javaconcurrencyinpractice.com/。

Answer 2

通过将商店日志移至单独的类

来解决

可以在线程中使用声明性服务吗？

2 个答案: