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