Java SNMP4J陷阱應用程序正在凍結GUI

Question

我在Java中有一個SNMP陷阱應用程序，旨在偵聽SNMP代理並在JFrame窗口的JTextArea上打印接收到的SNMP消息。

下面的第I部分是我的源代碼，顯示了類TrapReceiver的內容。在這堂課中，傾聽法是充分利用這個工作的地方。該類在我想在所提及的JTeaxtArea上顯示消息的JFrame類中進行了插入。我將JTextArea對象的引用，SNMP代理URL和端口發送到類TrapReceiver的構造函數中，然後調用TrapReceiver對象的run方法以在JFrame實例以外的單獨線程中啓動執行。下面的第二部分展示了我如何在JFrame實例中實例化TrapReceiver類。

當我運行應用程序時，我注意到JFrame實例（即GUI）凍結，並且沒有消息正在JFrame實例內的所謂JTeaxtArea上打印，實例化了下面第I部分中所示的類TrapRececeiver。

我的問題是爲什麼JFrame實例（即GUI）凍結，儘管TRapReceiver本身作爲單獨的線程執行？另外，我想知道這個凍結問題的可能解決方案是什麼。提前致謝。

P.S .:我已經驗證TrapReceiver工作正常，並且可以在沒有GUI的情況下作爲獨立應用程序運行時將消息打印到標準輸出，但由於某些可能的線程同步問題，它會以某種方式凍結。我試圖運行TrapReceiver而不把它放到線程中，即使在這種情況下，GUI仍然凍結。

PART我

package com.[Intenionally removed].snmp; 

import java.io.IOException; 
import javax.swing.JTextArea; 
import org.snmp4j.*; 
import org.snmp4j.mp.MPv1; 
import org.snmp4j.mp.MPv2c; 
import org.snmp4j.security.Priv3DES; 
import org.snmp4j.security.SecurityProtocols; 
import org.snmp4j.smi.OctetString; 
import org.snmp4j.smi.TcpAddress; 
import org.snmp4j.smi.TransportIpAddress; 
import org.snmp4j.smi.UdpAddress; 
import org.snmp4j.transport.AbstractTransportMapping; 
import org.snmp4j.transport.DefaultTcpTransportMapping; 
import org.snmp4j.transport.DefaultUdpTransportMapping; 
import org.snmp4j.util.MultiThreadedMessageDispatcher; 
import org.snmp4j.util.ThreadPool; 

public class TrapReceiver implements CommandResponder, Runnable { 

    private String targetSnmpAgentURL; 
    private int targetSnmpAgentPort; 
    private JTextArea outConsole; 

    public TrapReceiver() { 
    } 

    public TrapReceiver(JTextArea outConsole) { 
     this.outConsole = outConsole; 
    } 


    public TrapReceiver(JTextArea outConsole, String targetSnmpAgentURL, int targetSnmpAgentPort) { 
     this.targetSnmpAgentURL = targetSnmpAgentURL; 
     this.targetSnmpAgentPort = targetSnmpAgentPort; 
     this.outConsole = outConsole; 

     try { 
      listen(new UdpAddress(targetSnmpAgentURL + "/" + targetSnmpAgentPort)); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 
    } 

    public final synchronized void listen(TransportIpAddress address) throws IOException { 


     AbstractTransportMapping transport; 
     if (address instanceof TcpAddress) { 
      transport = new DefaultTcpTransportMapping((TcpAddress) address); 
     } else { 
      transport = new DefaultUdpTransportMapping((UdpAddress) address); 
     } 

     ThreadPool threadPool = ThreadPool.create("DispatcherPool", 10); 
     MessageDispatcher mDispathcher = new MultiThreadedMessageDispatcher(
      threadPool, new MessageDispatcherImpl()); 

     // add message processing models 
     mDispathcher.addMessageProcessingModel(new MPv1()); 
     mDispathcher.addMessageProcessingModel(new MPv2c()); 

     // add all security protocols 
     SecurityProtocols.getInstance().addDefaultProtocols(); 
     SecurityProtocols.getInstance().addPrivacyProtocol(new Priv3DES()); 

     // Create Target 
     CommunityTarget target = new CommunityTarget(); 
     target.setCommunity(new OctetString("public")); 

     Snmp snmp = new Snmp(mDispathcher, transport); 
     snmp.addCommandResponder(this); 

     transport.listen(); 
     System.out.println("Listening on " + address); 

     try { 
      this.wait(); 
     } catch (InterruptedException ex) { 
      Thread.currentThread().interrupt(); 
     } 
     } 

    /** 
    * This method will be called whenever a pdu is received on the given port 
    * specified in the listen() method 
    */ 
    @Override 
    public synchronized void processPdu(CommandResponderEvent cmdRespEvent) { 
     //System.out.println("Received PDU..."); 
     outConsole.append("Received PDU...\n"); 
     PDU pdu = cmdRespEvent.getPDU(); 

     if (pdu != null) {    
     outConsole.append("Trap Type = " + pdu.getType() + "\n"); 
     outConsole.append("Alarm Type: " + pdu.getVariableBindings().get(4) + "\n"); 
     outConsole.append("Alarm Message: " + pdu.getVariableBindings().get(9) + "\n\n"); 

     } 
    } 


    @Override 
    public void run() { 
     try {   
      listen(new UdpAddress(targetSnmpAgentURL + "/" + targetSnmpAgentPort)); 
     } catch (IOException e) { 
      outConsole.append("\nError occured while listening to SNMP messages: \n" + e.getMessage() + "\n\n"); 
     } 
    } 

} //end of class TrapReceiver 

PART II

在下面，我在一個線程中運行類的TrapReceiver的一個實例。

private void jButtonStartListeningSNMPActionPerformed(java.awt.event.ActionEvent evt) {               

    Thread snmpThread = 
      new Thread(new TrapReceiver(jTextAreaSNMPAlarmOutput, jTextFieldSnmpAgentUrl.getText().trim(), Integer.parseInt(jTextFieldSnmpAgentPort.getText().trim()))); 
    snmpThread.start() 

    } 

Answer 1

的問題是，你是在TrapReceiver構造函數，它發生在GUI線程上調用listen()。您只需要在run()方法中調用listen()，因爲這是新線程中發生的部分。