/*
* (C) Copyright 2006-2011 Nuxeo SA (http://nuxeo.com/) and others.
*
* 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.
*
* Contributors:
* bstefanescu
*/
package org.nuxeo.ecm.automation;
import org.nuxeo.ecm.automation.core.annotations.OperationMethod;
/**
* This interface is used to implement result collectors when an operation method is invoked over an iterable input.
* <p>
* The operation method usually declare a scalar type (e.g. data object) as argument. When the operation method is
* invoked on an iterator over elements of that type the execution of the chain may help you deal with this by
* automatically invoking your method over every element in the input iterator. For this to work you should set the
* collector that should be used by the automatic iteration {@link OperationMethod#collector()} in order to construct
* the method output.
* <p>
* So a collector is in fact collecting the result of each individual invocation over a collections of inputs. The
* collector will be asked by the chain execution to add an individual result by calling
* {@link #add(OperationContext, Object)}. This method is taking as argument the return value of the invocation - so it
* must accept the same type of object - see T generic type. When all partial results are collected the collector will
* be asked to return the operation result through the {@link #getOutput()} method.
* <p>
* So when writing a collector you <b>must</b> ensure that the collected type is compatible with the one returned by the
* operation method where the collector is used.
* <p>
* <b>IMPORTANT<> An implementation of this class must explicitly implements this interface (and not through its super
* classes). This is to ease generic type detections. If not doing so your collector class will be rejected and the
* operation using it invalid.
*
* @author <a href="mailto:bs@nuxeo.com">Bogdan Stefanescu</a>
*/
public interface OutputCollector<T, R> {
/**
* Collects a new partial result (the result of the last iteration step).
*/
void collect(OperationContext ctx, T obj) throws OperationException;
/**
* Gets the final output. This is usually a list or set of collected objects.
*/
R getOutput();
}