001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one
003 *  or more contributor license agreements.  See the NOTICE file
004 *  distributed with this work for additional information
005 *  regarding copyright ownership.  The ASF licenses this file
006 *  to you under the Apache License, Version 2.0 (the
007 *  "License"); you may not use this file except in compliance
008 *  with the License.  You may obtain a copy of the License at
009 *
010 *    http://www.apache.org/licenses/LICENSE-2.0
011 *
012 *  Unless required by applicable law or agreed to in writing,
013 *  software distributed under the License is distributed on an
014 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 *  KIND, either express or implied.  See the License for the
016 *  specific language governing permissions and limitations
017 *  under the License.
018 *
019 */
020package org.apache.mina.statemachine.context;
021
022/**
023 * Abstract {@link StateContextLookup} implementation. The {@link #lookup(Object[])}
024 * method will loop through the event arguments and call the {@link #supports(Class)}
025 * method for each of them. The first argument that this method returns 
026 * <tt>true</tt> for will be passed to the abstract {@link #lookup(Object)}
027 * method which should try to extract a {@link StateContext} from the argument.
028 * If none is found a new {@link StateContext} will be created and stored in the
029 * event argument using the {@link #store(Object, StateContext)} method.
030 *
031 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
032 */
033public abstract class AbstractStateContextLookup implements StateContextLookup {
034    private final StateContextFactory contextFactory;
035
036    /**
037     * Creates a new instance which uses the specified {@link StateContextFactory}
038     * to create {@link StateContext} objects.
039     * 
040     * @param contextFactory the factory.
041     */
042    public AbstractStateContextLookup(StateContextFactory contextFactory) {
043        if (contextFactory == null) {
044            throw new IllegalArgumentException("contextFactory");
045        }
046        this.contextFactory = contextFactory;
047    }
048
049    public StateContext lookup(Object[] eventArgs) {
050        for (int i = 0; i < eventArgs.length; i++) {
051            if (supports(eventArgs[i].getClass())) {
052                StateContext sc = lookup(eventArgs[i]);
053                if (sc == null) {
054                    sc = contextFactory.create();
055                    store(eventArgs[i], sc);
056                }
057                return sc;
058            }
059        }
060        return null;
061    }
062
063    /**
064     * Extracts a {@link StateContext} from the specified event argument which
065     * is an instance of a class {@link #supports(Class)} returns 
066     * <tt>true</tt> for.
067     * 
068     * @param eventArg the event argument.
069     * @return the {@link StateContext}.
070     */
071    protected abstract StateContext lookup(Object eventArg);
072
073    /**
074     * Stores a new {@link StateContext} in the specified event argument which
075     * is an instance of a class {@link #supports(Class)} returns 
076     * <tt>true</tt> for.
077     * 
078     * @param eventArg the event argument.
079     * @param context the {@link StateContext} to be stored.
080     */
081    protected abstract void store(Object eventArg, StateContext context);
082
083    /**
084     * Must return <tt>true</tt> for any {@link Class} that this
085     * {@link StateContextLookup} can use to store and lookup 
086     * {@link StateContext} objects.
087     * 
088     * @param c the class.
089     * @return <tt>true</tt> or <tt>false</tt>.
090     */
091    protected abstract boolean supports(Class<?> c);
092}