net.sf.eBus.client

Interface ERequestor

All Superinterfaces:

EObject

All Known Implementing Classes:

ERemoteApp

public interface ERequestor
extends EObject

Classes wanting to send eBus requests must implement this interface. A requestor must first successfully open a request feed and then send a request message. eBus forwards the request to all repliers matching the given request. If there are no matching repliers for the request, then ERequestFeed.request throws an IllegalStateexception with the message "no repliers for request". Otherwise, returns a ERequestFeed.ERequest feed instance. At this point, the requestor may expect to receive reply messages on the reply(int, EReplyMessage, ERequestFeed.ERequest) callback (or its replacement).

A request may be forwarded to more than one replier. Each replier may send more than one reply. A requestor knows when a final reply is received when the remaining parameter is zero.

A requestor may cancel a request any time before the final reply is received by calling ERequestFeed.ERequest.close(). The requestor may receive replies after this point if the reply messages were scheduled for delivery prior to canceling 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 requestor callbacks. This is done by calling ERequestFeed.statusCallback(FeedStatusCallback) and/or ERequestFeed.replyCallback(ReplyCallback) and using a lambda expression to specify the callback target. Still, the application must either override ERequestor interface methods or put callbacks in place. Failure to do either results in ERequestFeed.subscribe() failing. A class wishing to post requests must still implement ERequestor 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 reply callback can be used in conjunction with a feedStatus(EFeedState, ERequestFeed) override.

Author:

Charles Rapp

See Also:

EReplier, ERequestFeed.ERequest, ERequestFeed, ERequestMessage, EReplyMessage

Method Summary

Modifier and Type	Method and Description
default void	feedStatus(EFeedState feedState, ERequestFeed feed) eBus calls this method to inform the requestor that the request feed is either has at least one replier (up) or no repliers (down).
default void	reply(int remaining, EReplyMessage reply, ERequestFeed.ERequest request) eBus calls this method to deliver a reply message to the corresponding request.

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

shutdown, startup

Method Detail

feedStatus

default void feedStatus(EFeedState feedState,
                        ERequestFeed feed)

eBus calls this method to inform the requestor that the request feed is either has at least one replier (up) or no repliers (down). If down, then any call to ERequestFeed.request(ERequestMessage) will result in an IllegalStateException. If up, then a request will attempt to post to the advertised repliers.

Note that an IllegalStateException may still be thrown when the feed state is up because none of the repliers accepted the request.

Parameters:

feedState - the subscription's new feed state.

feed - the status applies to this feed.

Throws:

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

See Also:

reply(int, EReplyMessage, ERequestFeed.ERequest)

reply

default void reply(int remaining,
                   EReplyMessage reply,
                   ERequestFeed.ERequest request)

eBus calls this method to deliver a reply message to the corresponding request. The requestor can determine that this is the final reply to the request when remaining is zero.

Parameters:

remaining - the number of replies yet to be received. Zero means all replies received and no more will be forthcoming.

reply - the latest reply.

request - the reply is for this request.

Throws:

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

See Also:

feedStatus(EFeedState, ERequestFeed)