    001package org.apache.turbine.modules;
    002
    003/*
    004 * Licensed to the Apache Software Foundation (ASF) under one
    005 * or more contributor license agreements.  See the NOTICE file
    006 * distributed with this work for additional information
    007 * regarding copyright ownership.  The ASF licenses this file
    008 * to you under the Apache License, Version 2.0 (the
    009 * "License"); you may not use this file except in compliance
    010 * with the License.  You may obtain a copy of the License at
    011 *
    012 *   http://www.apache.org/licenses/LICENSE-2.0
    013 *
    014 * Unless required by applicable law or agreed to in writing,
    015 * software distributed under the License is distributed on an
    016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    017 * KIND, either express or implied.  See the License for the
    018 * specific language governing permissions and limitations
    019 * under the License.
    020 */
    021
    022import org.apache.turbine.Turbine;
    023import org.apache.turbine.pipeline.PipelineData;
    024
    025/**
    026 * The purpose of this class is to allow one to load and execute
    027 * Navigation modules.
    028 *
    029 * @author <a href="mailto:mbryson@mont.mindspring.com">Dave Bryson</a>
    030 * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
    031 * @author <a href="mailto:peter@courcoux.biz">Peter Courcoux</a>
    032 * @version $Id: NavigationLoader.java 1709648 2015-10-20 17:08:10Z tv $
    033 */
    034public class NavigationLoader
    035    extends GenericLoader<Navigation>
    036    implements Loader<Navigation>
    037{
    038    /** The single instance of this class. */
    039    private static NavigationLoader instance = new NavigationLoader();
    040
    041    /**
    042     * These ctor's are private to force clients to use getInstance()
    043     * to access this class.
    044     */
    045    private NavigationLoader()
    046    {
    047        super();
    048    }
    049
    050    /**
    051     * Attempts to load and execute the external Navigation. This is
    052     * used when you want to execute a Navigation which returns its
    053     * output via a MultiPartElement instead of out the data.getPage()
    054     * value.  This allows you to easily chain the execution of
    055     * Navigation modules together.
    056     *
    057     * @param pipelineData Turbine information.
    058     * @param name Name of object that will execute the navigation.
    059     * @return the navigation module output
    060     * @exception Exception a generic exception.
    061     */
    062    public String eval(PipelineData pipelineData, String name)
    063            throws Exception
    064    {
    065        // Execute Navigation
    066        return getAssembler(name).build(pipelineData);
    067    }
    068
    069    /**
    070     * Attempts to load and execute the external Navigation.
    071     *
    072     * @param pipelineData Turbine information.
    073     * @param name Name of object instance.
    074     * @exception Exception a generic exception.
    075     */
    076    @Override
    077    public void exec(PipelineData pipelineData, String name)
    078                throws Exception
    079    {
    080        this.eval(pipelineData, name);
    081    }
    082
    083    /**
    084     * Pulls out an instance of the object by name.  Name is just the
    085     * single name of the object.
    086     *
    087     * @param name Name of object instance.
    088     * @return A Layout with the specified name, or null.
    089     * @exception Exception a generic exception.
    090     */
    091    @Override
    092    public Navigation getAssembler(String name)
    093        throws Exception
    094    {
    095        return getAssembler(Navigation.class, name);
    096    }
    097
    098    /**
    099     * @see org.apache.turbine.modules.Loader#getCacheSize()
    100     */
    101    @Override
    102    public int getCacheSize()
    103    {
    104        return NavigationLoader.getConfiguredCacheSize();
    105    }
    106
    107    /**
    108     * The method through which this class is accessed.
    109     *
    110     * @return The single instance of this class.
    111     */
    112    public static NavigationLoader getInstance()
    113    {
    114        return instance;
    115    }
    116
    117    /**
    118     * Helper method to get the configured cache size for this module
    119     *
    120     * @return the configure cache size
    121     */
    122    private static int getConfiguredCacheSize()
    123    {
    124        return Turbine.getConfiguration().getInt(Navigation.CACHE_SIZE_KEY,
    125                Navigation.CACHE_SIZE_DEFAULT);
    126    }
    127}