net.sf.eBus.client

Interface EReplier

All Superinterfaces:

EObject

All Known Implementing Classes:

ERemoteApp

public interface EReplier
extends EObject

Classes able to reply to eBus requests must implement this interface. A replier must:

1. open the reply feed,
2. advertise this reply ability, and
3. declare with an up feed state that it (the replier) is ready to handle requests.

The message key used in opening the feed must be a request message class.

A replier can retract an advertisement by calling EReplyFeed.unadvertise(). The reply feed is discarded by calling EFeed.close(). If a replier is temporarily unable to reply to a request, then updateFeedState(EFeedState.DOWN) should be used rather than un-advertising. When the replier is again able to respond, updateFeedState(EFeedState.UP) is called.

Requests matching the advertised reply feed are forwarded as EReplyFeed.ERequest instances via the request(EReplyFeed.ERequest) callback. Replies are sent via EReplyFeed.ERequest.reply(net.sf.eBus.messages.EReplyMessage).

Note: the replier is limited to reply messages specified in the request message's EReplyInfo annotation or in the request message super class (EReplyInfo is inherited). If the reply message is not a member of EReplyInfo.replyMessageClasses(), then it will be rejected.

If a requestor cancels a request, the replier is informed by the cancelRequest(EReplyFeed.ERequest) callback. The request is unilaterally ended by the requestor and the replier may no longer send replies to the request.

As of eBus v. 4.2.0, implementing the interface methods is no longer necessary. Instead, Java lambda expressions may be used to handle replier callbacks. This is done by calling EReplyFeed.requestCallback(RequestCallback) and/or EReplyFeed.cancelRequestCallback(CancelRequestCallback) and passing a lambda expression to specify the callback target. Still, the application must either override EReplier interface methods or put callbacks in place. Failure to do either results in EReplyFeed.advertise() failing. A class wishing to receive requests must still implement EReplier even though it is no longer necessary to override the interface methods.

It is possible to mix and match EReplier overrides and callbacks. That is, a request callback can be used in conjunction with a cancelRequest(EReplyFeed.ERequest) override.

eBus maintains a weak reference to application objects. If a replier is garbage collected without un-advertising and closing its reply feed, eBus automatically closes the feed and posts failure replies to all active requests.

Author:

Charles Rapp

See Also:

ERequestor, EReplyFeed.ERequest, EReplyFeed, ERequestMessage, EReplyMessage

Method Summary

Modifier and Type	Method and Description
default void	cancelRequest(EReplyFeed.ERequest request) The specified request is canceled by the requestor.
default void	request(EReplyFeed.ERequest request) An incoming request.

Methods inherited from interface net.sf.eBus.client.EObject

shutdown, startup

Method Detail

request

default void request(EReplyFeed.ERequest request)

An incoming request. The replier may send a reply either from within this method call or asynchronously after returning from this method. If the reply is sent asynchronously, then the replier must store request for later use. Replies are sent using ERequest and not EReplyFeed.

The request message is stored in request and can be retrieved by calling EReplyFeed.ERequest.request().

The request matches the replier's open and advertised feed. The associated EReplyFeed may be retrieved by calling EReplyFeed.ERequest.replier().

Parameters:

request - post replies via this request.

Throws:

UnsupportedOperationException - if implementing class does not override this method nor uses a callback.

See Also:

cancelRequest(EReplyFeed.ERequest)

cancelRequest

default void cancelRequest(EReplyFeed.ERequest request)

The specified request is canceled by the requestor. The request is shut down and no further replies will be accepted. However, in-flight replies posted prior to cancellation may still be delivered.

The request matches the replier's open and advertised feed. The associated EReplyFeed may be retrieved by calling EReplyFeed.ERequest.replier().

Parameters:

request - cancel this request.

Throws:

UnsupportedOperationException - if implementing class does not override this method nor uses a callback.

See Also:

request(EReplyFeed.ERequest)