org.lsst.ccs.messaging

Interface BusMessagePreProcessor

All Known Implementing Classes:

AgentStateService

public interface BusMessagePreProcessor

Interface to be implemented by Agent Services that wish to modify the content of an incoming BusMessage. Objects implementing this interface are automatically registered with the MessagingAccessLayer after the HasLifecycle::build step with the appropriate bus. All the BusMessagePreProcessor interfaces are called to pre-process incoming BusMessages before any MessageListeners are called. This interface allows Agent Services to introduce a layer of separation between the messages sent on the CCS buses and the messages offered to MessageListeners.

Author:

The LSST CCS Team

Method Summary

Modifier and Type	Method and Description
Bus	getBus() The Bus this BusMessagePreProcessor applies to.
BusMessage	preProcessMessage(BusMessage msg) Pre-process the incoming BusMessage and return the message to be forwarded to the bus message listeners.

Method Detail

preProcessMessage

BusMessage preProcessMessage(BusMessage msg)

Pre-process the incoming BusMessage and return the message to be forwarded to the bus message listeners. The returned message can either be a modified version of the original message or a brand new message. The Class of the returned message can be different than the incoming message. If null is returned the message will not be sent to the BusMessage listeners, but it will still be passed to other BusMessagePreProcessors This method can be invoked by separate threads, but it's invoked by one thread at a time; there is no concurrent invocation of the method.

Parameters:

msg - The incoming BusMessage

Returns:

The modified BusMessage to be forwarded to the BusMessageListeners

getBus

Bus getBus()

The Bus this BusMessagePreProcessor applies to.

Returns:

The Bus.