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/*
* Copyright (c) 2015 Torsten Krause, Markenwerk GmbH
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package net.markenwerk.commons.interfaces;
import java.lang.ref.WeakReference;
/**
* For an arbitrary process, that will eventually yield a result, a
* {@link Callback} is used, to convey that result from the executor of the
* process (the callee) back to the initiator of the process (the caller).
*
*
* Depending on the concrete scenario, the caller may reuse the same instance of
* {@link Callback} for multiple processes and even for the same callee..
*
*
* In most scenarios, the callee must eventually call
* {@link Callback#onResult(Object, Object)}, at least once.
*
*
* A useful exception to this rule is, when the callee can ensure, that the
* result wont't be needed by the caller, because the caller itself is not
* needed anymore. This is usually implemented by placing the {@link Callback}
* in a {@link WeakReference}. Because using anonymous instances of
* {@link Callback} will most likely fail in this situation, it should be noted
* in the contract of the method, that takes the {@link Callback} as an
* argument.
*
*
* The callee may call {@link Callback#onResult(Object, Object)}, more than
* once, depending o the concrete scenario, to convey partial or updated
* results. This should be noted in the contract of the method, takes the
* {@link Callback} as an argument.
*
*
* The callee must not call {@link Callback#onResult(Object, Object)} more than
* once for the same result.
*
* @param
* The type of the original
* @param
* The type of the result of the process.
* @since 1.0.0
* @author Torsten Krause (tk at markenwerk dot net)
*/
public interface Callback {
/**
* Called by the callee if and when a result is available.
*
*
* Implementers must not throw any exceptions.
*
* @param callee
* The callee.
* @param result
* The result.
*/
public void onResult(Callee callee, Result result);
}