tiles-core/src/main/java/org/apache/tiles/impl/KeyedDefinitionsFactoryTilesContainer.java

/*
 * $Id$
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.tiles.impl;

import java.util.HashMap;
import java.util.Map;

import org.apache.tiles.Definition;
import org.apache.tiles.TilesException;
import org.apache.tiles.context.TilesRequestContext;
import org.apache.tiles.definition.DefinitionsFactory;
import org.apache.tiles.definition.DefinitionsFactoryException;

/**
 * Container that can be used to store multiple {@link DefinitionsFactory}
 * instances mapped to different keys.
 *
 * @version $Rev$ $Date$
 */
public class KeyedDefinitionsFactoryTilesContainer extends BasicTilesContainer {

    /**
     * Constant representing the prefix of the configuration parameter used to
     * define the tiles definition resources for a specific key.
     */
    public static final String DEFINITIONS_CONFIG_PREFIX =
        "org.apache.tiles.impl.KeyedDefinitionsFactoryTilesContainer.DEFINITIONS_CONFIG@";

    /**
     * Maps definition factories to their keys.
     */
    protected Map<String, DefinitionsFactory> key2definitionsFactory;

    /**
     * The key extractor object.
     */
    protected KeyExtractor keyExtractor;

    /**
     * Constructor.
     */
    public KeyedDefinitionsFactoryTilesContainer() {
        key2definitionsFactory = new HashMap<String, DefinitionsFactory>();
    }

    /**
     * It represents an object able to return a key from a request. Each key
     * maps a different {@link DefinitionsFactory}.
     */
    public static interface KeyExtractor {

        /**
         * Returns the definitions factory key.
         *
         * @param request The request object.
         * @return The needed factory key.
         */
        String getDefinitionsFactoryKey(TilesRequestContext request);
    }

    /**
     * This is the default factory key. Takes the key from the request-scoped
     * attribute <code>DEFINITIONS_FACTORY_KEY_ATTRIBUTE_NAME</code>.
     */
    public static class DefaultKeyExtractor implements KeyExtractor {

        /**
         * Name of the attribute inside the request that will be used to get the
         * key of the definitions factory to be used.
         */
        public static final String DEFINITIONS_FACTORY_KEY_ATTRIBUTE_NAME =
            "org.apache.tiles.impl.KeyedDefinitionsFactoryTilesContainer.DefaultKeyExtractor.KEY";

        /**
         * Returns the definitions factory key.
         *
         * @param request The request object.
         * @return The needed factory key.
         */
        public String getDefinitionsFactoryKey(TilesRequestContext request) {
            String retValue = null;
            Map<String, Object> requestScope = request.getRequestScope();
            if (requestScope != null) { // Probably the request scope does not exist
                retValue = (String) requestScope.get(
                        DEFINITIONS_FACTORY_KEY_ATTRIBUTE_NAME);
            }

            return retValue;
        }
    }

    /**
     * Returns a definition factory given its key.
     *
     * @return the definitions factory used by this container. If the key is not
     * valid, the default factory will be returned.
     * @param key The key of the needed definitions factory.
     */
    public DefinitionsFactory getDefinitionsFactory(String key) {
        DefinitionsFactory retValue = null;

        if (key != null) {
            retValue = key2definitionsFactory.get(key);
        }
        if (retValue == null) {
            retValue = getDefinitionsFactory();
        }

        return retValue;
    }

    /**
     * Returns the proper definition factory for the given key, i.e. if the key
     * is not present, <code>null</code> will be returned.
     *
     * @return the definitions factory used by this container. If the key is not
     * valid, <code>null</code> will be returned.
     * @param key The key of the needed definitions factory.
     */
    public DefinitionsFactory getProperDefinitionsFactory(String key) {
        DefinitionsFactory retValue = null;

        if (key != null) {
            retValue = key2definitionsFactory.get(key);
        }

        return retValue;
    }

    /**
     * Set the definitions factory. This method first ensures
     * that the container has not yet been initialized.
     *
     * @param key The key under which the definitions factory is catalogued.
     * @param definitionsFactory the definitions factory for this instance.
     * @param initParameters The init parameters to configure the definitions
     * factory.
     * @throws TilesException If something goes wrong during initialization of
     * the definitions factory.
     */
    public void setDefinitionsFactory(String key,
            DefinitionsFactory definitionsFactory,
            Map<String, String> initParameters) throws TilesException {
        if (key != null) {
            key2definitionsFactory.put(key, definitionsFactory);
            initializeDefinitionsFactory(definitionsFactory,
                    getResourceString(initParameters), initParameters);
        } else {
            setDefinitionsFactory(definitionsFactory);
        }
    }

    /**
     * Sets the key extractor to use.
     *
     * @param keyExtractor The key extractor.
     */
    public void setKeyExtractor(KeyExtractor keyExtractor) {
        this.keyExtractor = keyExtractor;
    }

    /** {@inheritDoc} */
    @Override
    protected Definition getDefinition(String definitionName,
            TilesRequestContext request) throws DefinitionsFactoryException {
        Definition retValue = null;
        String key = getDefinitionsFactoryKey(request);
        if (key != null) {
            DefinitionsFactory definitionsFactory =
                key2definitionsFactory.get(key);
            if (definitionsFactory != null) {
                retValue = definitionsFactory.getDefinition(definitionName,
                        request);
            }
        }
        if (retValue == null) {
            retValue = super.getDefinition(definitionName, request);
        }
        return retValue;
    }

    /**
     * Returns the definitions factory key.
     *
     * @param request The request object.
     * @return The needed factory key.
     */
    protected String getDefinitionsFactoryKey(TilesRequestContext request) {
        if (keyExtractor == null) {
            keyExtractor = new DefaultKeyExtractor();
        }
        return keyExtractor.getDefinitionsFactoryKey(request);
    }
}