SNMP Trap Handler

A trap handler for the SNMP manager is an object that implements the SnmpTrapListener interface in the javax.management.snmp.manager package. When this object is bound as a listener of an SnmpEventReportDispatcher object, its methods will be called to handle trap PDUs.

A trap listener is not a notification listener because the dispatcher is not a notification broadcaster. The listener has callback methods that the work in the same manner, but they are given objects that represent traps, not instances of the Notification class.

The interface defines two methods, one for processing SNMPv1 traps and the other for SNMPv2 traps. Trap PDU packets have already been decoded by the dispatcher, and these methods handle an object representation of the trap: SnmpPduTrap objects for v1 and SnmpPduRequest objects for v2. In our implementation, we are only interested in v1 traps, and we just print out the trap information fields.

Example 17-2 The SnmpTrapListener Implementation

public class TrapListenerImpl implements SnmpTrapListener {

    public void processSnmpTrapV1(SnmpPduTrap trap) {
        java.lang.System.out.println(
            "NOTE: TrapListenerImpl received trap :");
        java.lang.System.out.println(
            "\tGeneric " + trap.genericTrap);
        java.lang.System.out.println(
            "\tSpecific " + trap.specificTrap);
        java.lang.System.out.println(
            "\tTimeStamp " + trap.timeStamp);
        java.lang.System.out.println(
            "\tAgent address " + trap.agentAddr.stringValue());
    }

    public void processSnmpTrapV2(SnmpPduRequest trap) {
        java.lang.System.out.println("NOTE: Trap V2 ignored");
    }
}