net.sf.eBus.client.ECondition Maven / Gradle / Ivy
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//
// Copyright 2009, 2011, 2015, 2016 Charles W. Rapp
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
package net.sf.eBus.client;
import net.sf.eBus.messages.EMessage;
/**
* This interface allows {@link ESubscribeFeed} and
* {@link EReplyFeed} to automatically test a message in order
* to determine if it should be passed on to a client. If
* {@link ECondition#test(EMessage) test} returns {@code true}
* eBus forwards the message to the client. If {@code test}
* returns {@code false} or throws an exception, then the message
* is not forwarded.
*
* In eBus v. 4.2.0, this interface is now marked as a
* {@code @FunctionalInterface}, allowing this interface to be
* defined using a Java lambda expression.
*
*
* @author Charles Rapp
*/
@FunctionalInterface
public interface ECondition
{
//--------------------------------------------------------------
// Member methods.
//
/**
* Returns {@code true} if the message meets this condition
* and so should be passed to the eBus client; {@code false}
* if the message should not be passed on. If this method
* throws an exception, it is treated the same as having
* returned {@code false}.
* @param msg The tested notification message.
* @return {@code true} if the message meets this condition
* and so should be passed to the eBus client.
*/
boolean test(EMessage msg);
} // end of interface ECondition