[SNMP4J] Need help:Unable to run sample snmp code with OIDs

[anshul gupta]

Hi,	We are working on college project. We are unable to solve the
 problem that we have come up while coding. Please, help us.Here is our code.
//import java.net.InetAddress;import
 org.snmp4j.CommunityTarget;import org.snmp4j.PDU;import
 org.snmp4j.Snmp;import org.snmp4j.TransportMapping;import org.snmp4j.event.ResponseEvent;import org.snmp4j.event.ResponseListener;import org.snmp4j.mp.SnmpConstants;import org.snmp4j.smi.*;import org.snmp4j.transport.DefaultUdpTransportMapping;//import java.lang.NullPointerException;public class SNMP4JHelper{	public static final int SNMP_PORT = 161;	public static final String READ_COMMUNITY = "public";	public static final String WRITE_COMMUNITY= "private";	public static final int mSNMPVersion =0; // 0 represents
 SNMP version=1	public static final String OID_Hard_disk = "1.3.6.1.2.1.1.3.0";//	 "1.3.6.1.4.1.2021.9.1.7.1";//		".1.3.6.1.4.1.2021.4.4.0";//
	
	"1.3.6.1.4.1.311.1.1.3.1.1.5.1.3";		//"1.3.6.1.4.1.318.1.1.1.12.3.2.1.3.1";	//public static final String OID_UPS_BATTERY_CAPACITY="1.3.6.1.4.1.318.1.1.1.2.2.1.0";	public static void main(String[] args)	{		try		{//			"172.20.1.150"			String strIPAddress = "127.0.0.1";			SNMP4JHelper objSNMP = new SNMP4JHelper();					//objSNMP.snmpSet();		int Value = 1;			///////////////////////////////////////////			//Set Value=2 to trun OFF UPS OUTLET
 Group1			//Value=1 to trun ON UPS OUTLET Group1			//////////////////////////////////////////					//	"strIPAddress, WRITE_COMMUNITY,OID_Hard_disk, Value"		//	UPS_OUTLET_GROUP1			objSNMP.snmpSet(strIPAddress, WRITE_COMMUNITY,OID_Hard_disk,
 Value);		

	//////////////////////////////////////////////////////////			//Get Basic state of UPS			/////////////////////////////////////////////////////////		
	String batteryCap =objSNMP.snmpGet(strIPAddress,READ_COMMUNITY,OID_Hard_disk);	

	}		catch (Exception e)		{			e.printStackTrace();		}
	}	/*	 * The following code valid only SNMP version1. This	 * method is very useful to set a parameter on remote device.	 * */	 	public void snmpSet(String strAddress, String community, String strOID, int Value)	{		strAddress= strAddress+"/"+SNMP_PORT;		Address
 targetAddress = GenericAddress.parse(strAddress);		Snmp snmp;		try		{			TransportMapping transport
 = new DefaultUdpTransportMapping();			snmp = new Snmp(transport);			transport.listen();			CommunityTarget target = new CommunityTarget();			target.setCommunity(new OctetString(community));			target.setAddress(targetAddress);			target.setRetries(2);			target.setTimeout(5000);			target.setVersion(SnmpConstants.version1);			PDU pdu = new PDU();//			pdu.add(new VariableBinding(new OID(strOID), new Integer32(Value)));			pdu.setType(PDU.SET);			ResponseListener listener = new ResponseListener() 			{				public void onResponse(ResponseEvent event) 			
	{					// Always cancel async request when response has been received					// otherwise a memory leak is created! Not canceling a request				

	// immediately can be
 useful when sending a request to a broadcast					// address					((Snmp)event.getSource()).cancel(event.getRequest(), this);					if ( event.getResponse() != null )					{						System.out.println("Set Status is:"+event.getResponse().getErrorStatusText());					}				}			};		

	snmp.send(pdu, target, null, listener);						snmp.close();		
			}		catch (Exception e)		{			e.printStackTrace();		}	}	/*	 * The code is valid only SNMP version1.
 SnmpGet method	 * return Response for given OID from the Device.	 */	 	public
 String snmpGet(String strAddress, String community, String strOID)	{		String str="";		try		{		

	OctetString comm1 = new OctetString(community);			strAddress= strAddress+"/"+ SNMP_PORT;			Address targetaddress = new UdpAddress(strAddress);		
	TransportMapping transport = new DefaultUdpTransportMapping();			transport.listen();			CommunityTarget comtarget = new CommunityTarget();			comtarget.setCommunity(comm1);			comtarget.setVersion(SnmpConstants.version1);			comtarget.setAddress(targetaddress);			comtarget.setRetries(2);			comtarget.setTimeout(5000);			PDU pdu = new PDU();			ResponseEvent response;			Snmp snmp;			pdu.add(new VariableBinding(new OID(strOID)));			pdu.setType(PDU.GET);			snmp = new Snmp(transport);			response =
 snmp.get(pdu,comtarget);			if(response != null)			{				System.out.println( "Error msg : " + response.getError().toString() );				if(response.getResponse().getErrorStatusText().equalsIgnoreCase("Success"))				{					PDU pduresponse=response.getResponse();					str=pduresponse.getVariableBindings().firstElement().toString();					if(str.contains("="))	
	
	
		{						int len = str.indexOf("=");						str=str.substring(len+1, str.length());					}				}		
	}			else			{				System.out.println("Feeling like a TimeOut occured ");			}			snmp.close();		} catch(Exception e) 		{ e.printStackTrace(); }		System.out.println("Response="+str);		return str;	}}
On running the code::::::
java.lang.NullPointerExceptionResponse=	at SNMP4JHelper.snmpGet(SNMP4JHelper.java:131)	at SNMP4JHelper.main(SNMP4JHelper.java:45)
Please guide
 us.Thank you.