SnmpHelperFull.java

package com.mulesoft;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.snmp4j.CommandResponder;
import org.snmp4j.CommandResponderEvent;
import org.snmp4j.MessageDispatcher;
import org.snmp4j.MessageDispatcherImpl;
import org.snmp4j.PDU;
import org.snmp4j.Snmp;
import org.snmp4j.mp.MPv1;
import org.snmp4j.mp.MPv2c;
import org.snmp4j.mp.MPv3;
import org.snmp4j.security.AuthMD5;
import org.snmp4j.security.PrivDES;
import org.snmp4j.security.SecurityModels;
import org.snmp4j.security.SecurityProtocols;
import org.snmp4j.security.USM;
import org.snmp4j.security.UsmUser;
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 SnmpHelper implements CommandResponder {

    private static final String THREAD_POOL_NAME = "SnmpDispatcherPool";
    
    private static final OctetString SECURITY_NAME = new OctetString("SECURITY");
    private static final byte[] ENGINE_ID = MPv3.createLocalEngineID();

    private final List<PDU> pduList;
    private ThreadPool threadPool;
    private Snmp snmp;

    /**
     * SNMP version 1 and 2c.
     */
    public static SnmpHelper getLocalhostCommunityTargetInstance(int port) {
        final SnmpHelper snmpHelper = new SnmpHelper();
        try {
            snmpHelper.listenForTrapCommunityTarget("localhost", port);
        } catch (IOException e) {
            throw new RuntimeException("Snmp Community Target setup", e);
        }
        return snmpHelper;
    }
    
    /**
     * SNMP version 3.
     */
    public static SnmpHelper getLocalhostUserTargetInstance(int port, String userName, String password, String passphrase) {
        final SnmpHelper snmpHelper = new SnmpHelper();
        try {
            snmpHelper.listenForTrapUserTarget("localhost", port, userName, password, passphrase);
        } catch (IOException e) {
            throw new RuntimeException("Snmp User Target setup", e);
        }
        return snmpHelper;
    }

    private SnmpHelper() {
        pduList = new ArrayList<PDU>();
    }

    /**
     * @param host (eg. "localhost")
     * @param port (eg. "164")
     */
    private synchronized void listenForTrapCommunityTarget(String host, int port) throws IOException {
        final TransportIpAddress address = new UdpAddress(host + "/" + port);
        final AbstractTransportMapping transport;
        if (address instanceof TcpAddress) {
            transport = new DefaultTcpTransportMapping((TcpAddress) address);
        } else {
            transport = new DefaultUdpTransportMapping((UdpAddress) address);
        }

        threadPool = ThreadPool.create(THREAD_POOL_NAME, 10);
        final MessageDispatcher multiThreadMessagetDispatcher = new MultiThreadedMessageDispatcher(threadPool, new MessageDispatcherImpl());

        // Add message processing models.
        multiThreadMessagetDispatcher.addMessageProcessingModel(new MPv1());
        multiThreadMessagetDispatcher.addMessageProcessingModel(new MPv2c());

        SecurityProtocols.getInstance().addDefaultProtocols();
        snmp = new Snmp(multiThreadMessagetDispatcher, transport);
        snmp.addCommandResponder(this);
        transport.listen();
    }
    
    /**
     * @param host (eg. "localhost")
     * @param port (eg. "164")
     */
    private synchronized void listenForTrapUserTarget(String host, int port, String userName, String password, String passphrase) throws IOException {
        final TransportIpAddress address = new UdpAddress(host + "/" + port);

        final AbstractTransportMapping transport;
        if (address instanceof TcpAddress) {
            transport = new DefaultTcpTransportMapping((TcpAddress) address);
        } else {
            transport = new DefaultUdpTransportMapping((UdpAddress) address);
        }
        threadPool = ThreadPool.create(THREAD_POOL_NAME, 10);
        final MessageDispatcher multiThreadMessagetDispatcher = new MultiThreadedMessageDispatcher(threadPool, new MessageDispatcherImpl());

        // Add message processing models.
        multiThreadMessagetDispatcher.addMessageProcessingModel(new MPv3());
        SecurityProtocols.getInstance().addDefaultProtocols();
        snmp = new Snmp(multiThreadMessagetDispatcher, transport);
       
        // User Based Security Model.
        final USM usm = createSecurityModel(userName, password, passphrase);

        SecurityModels.getInstance().addSecurityModel(usm);
        snmp.addCommandResponder(this);
        transport.listen();
    }
    
    protected USM createSecurityModel(String userName, String password, String passphrase) {
        final USM usm = new USM(SecurityProtocols.getInstance(), new OctetString(ENGINE_ID), 0);
        final UsmUser user = new UsmUser(SECURITY_NAME, AuthMD5.ID, new OctetString(password), PrivDES.ID,  new OctetString(passphrase));
        usm.addUser(new OctetString(userName), user);
        return usm;
    }
    

    /**
     * This method will be called whenever a PDU is received on the given port specified when
     * instantiating this class.
     */
    @Override
    public synchronized void processPdu(CommandResponderEvent commandResponderEvent) {
        if (commandResponderEvent == null) {
            throw new RuntimeException("Command Responder Event expected to be not null");
        }
        final PDU pdu = commandResponderEvent.getPDU();
        if (pdu != null) {
            if (pdu.getErrorStatus() == PDU.noError) {
                addPduToList(pdu);
            } else {
                throw new RuntimeException("Error while retrieving PDU trap fro SNMP: Error Status: " + pdu.getErrorStatus() + ", Error Index: " + pdu.getErrorIndex()
                        + ", Error Status Text: " + pdu.getErrorStatusText());
            }
        }
    }

    public synchronized void clearPduList() {
        pduList.clear();
    }

    public synchronized void addPduToList(PDU pdu) {
        pduList.add(pdu);
    }

    public synchronized List<PDU> getPduList() {
        return pduList;
    }

    public synchronized void releaseInstance() {
        if (threadPool != null) {
            threadPool.stop();
        }
        try {
            if (snmp != null) {
                snmp.close();
            }
        } catch (IOException e) {
            // Do nothing.
        }
    }

    public synchronized List<PDU> getPduListAndClear() {
        final List<PDU> result = new ArrayList<PDU>(getPduList());
        clearPduList();
        return result;
    }

    @Override
    public void finalize() throws Throwable {
        releaseInstance();
        super.finalize();
    }
}

Hi guys,

Why do you use ThreadPool with value 10? Can you explain for me?