002 * (C) Copyright 2006-2011 Nuxeo SA (http://nuxeo.com/) and others.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *     http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 *
016 * Contributors:
017 *     bstefanescu
018 */
019package org.nuxeo.ecm.automation.core.annotations;
021import java.lang.annotation.ElementType;
022import java.lang.annotation.Retention;
023import java.lang.annotation.RetentionPolicy;
024import java.lang.annotation.Target;
026import org.nuxeo.ecm.automation.OutputCollector;
029 * To be used to mark methods provided by an operation. A method must have at most one argument which is the operation
030 * input and a return type which is the operation output. Methods with zero parameters (void input) will match any
031 * input. An operation may have multiple methods if it supports multiple input and output types.
032 * <p>
033 * For each INPUT/OUTPUT type association you must create a new method in an operation and annotate it using this
034 * annotation. The set of input types available in an operation are the operation accepted types and the set of output
035 * types are the operation produced types. A produced type will become the input type for the next operation in the
036 * chain, that will be dispatched to the right method that know how to consume the type.
037 * <p>
038 * When an operation provides 2 methods accepting the same input type the chain will need to take a decision to
039 * determine the best way to continue. A common algorithm to find the right path until the end of the chain is
040 * backtracking: from a set of potential nodes one is selected to be visited (randomly or not). If the node is a dead
041 * end then another node from the set is taken until the path to the last node is created.
042 * <p>
043 * A chain may have no paths until the last operation. In this case the chain is invalid and the chain processor will
044 * trigger an error. Also, a chain can provide multiple paths to the last operation. To help the engine to find the best
045 * path until the last operation you can use the {@link #priority()} attribute to specify which method is preferred. The
046 * default priority is 0 (e.g. no priority). Higher priorities have more chance to be selected when a conflict occurs.
047 * If no user priority is specified (i.e. priority is 0) then the default priority is used. Here is how the default
048 * priority is computed (the top most case has the greater priority):
049 * <ul>
050 * <li>The input type is an exact match of the method declared argument
051 * <li>The method argument type is assignable from the input type (i.e. a super type but not an exact match)
052 * <li>The input can be adapted to the method argument using registered type adapters
053 * <li>the method has no arguments (void input)
054 * </ul>
055 * If no one of these rules applies then the method will not match the input.
056 * <p>
057 * The class owning the annotated method must be annotated using {@link Operation}
058 *
059 * @author <a href="mailto:bs@nuxeo.com">Bogdan Stefanescu</a>
060 */
063public @interface OperationMethod {
065    /**
066     * If defined the method is iterable.
067     * <p>
068     * It means that when such a method is called with an input type of <code>Iterable<INPUT></code> (where INPUT is the
069     * declared method input type) the method will be iteratively called to generate all the outputs and collect them
070     * using the given OutputCollector.
071     *
072     * @return
073     */
074    @SuppressWarnings("rawtypes")
075    Class<? extends OutputCollector> collector() default OutputCollector.class;
077    int priority() default 0;