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 java.util.ArrayList;
023import java.util.List;
024
025import org.apache.turbine.Turbine;
026import org.apache.turbine.TurbineConstants;
027import org.apache.turbine.pipeline.PipelineData;
028import org.apache.turbine.services.TurbineServices;
029import org.apache.turbine.services.assemblerbroker.AssemblerBrokerService;
030
031/**
032 * This is the base class for the loaders. It contains code that is
033 * used across all of the loaders. It also specifies the interface
034 * that is required to be called a Loader.
035 *
036 * @author <a href="mailto:mbryson@mont.mindspring.com">Dave Bryson</a>
037 * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
038 * @author <a href="mailto:peter@courcoux.biz">Peter Courcoux</a>
039 * @param <T> the specialized assembler type
040 */
041public abstract class GenericLoader<T extends Assembler>
042{
043    /** The Assembler Broker Service */
044    protected AssemblerBrokerService ab;
045
046    /** @serial This can be serialized */
047    private boolean reload = false;
048
049    /** Base packages path for Turbine */
050    private static final String TURBINE_PACKAGE = "org.apache.turbine.modules";
051
052    /** Packages paths for Turbine */
053    private static List<String> TURBINE_PACKAGES = null;
054
055    /**
056     * Basic constructor for creating a loader.
057     */
058    public GenericLoader()
059    {
060        super();
061        ab = (AssemblerBrokerService)TurbineServices.getInstance().getService(AssemblerBrokerService.SERVICE_NAME);
062    }
063
064    /**
065     * Attempts to load and execute the external action that has been
066     * set.
067     * @param pipelineData the Turbine request
068     * @param name the name of the assembler module
069     * @throws Exception a generic exception.
070     */
071    public abstract void exec(PipelineData pipelineData, String name)
072            throws Exception;
073
074    /**
075     * Returns whether or not this external action is reload itself.
076     * This is in cases where the Next button would be clicked, but
077     * since we are checking for that, we would go into an endless
078     * loop.
079     *
080     * @return True if the action is reload.
081     */
082    public boolean reload()
083    {
084        return this.reload;
085    }
086
087    /**
088     * Sets whether or not this external action is reload itself.
089     * This is in cases where the Next button would be clicked, but
090     * since we are checking for that, we would go into an endless
091     * loop.
092     *
093     * @param reload True if the action must be marked as reload.
094     * @return Itself.
095     */
096    public GenericLoader<T> setReload(boolean reload)
097    {
098        this.reload = reload;
099        return this;
100    }
101
102    /**
103     * Gets the base package where Turbine should find its default
104     * modules.
105     *
106     * @return A String with the base package name.
107     */
108    public static String getBasePackage()
109    {
110        return TURBINE_PACKAGE;
111    }
112
113    /**
114     * Gets the package list where Turbine should find its
115     * modules.
116     *
117     * @return A List with the package names (including the base package).
118     */
119    public static List<String> getPackages()
120    {
121        if (TURBINE_PACKAGES == null)
122        {
123            List<String> turbinePackages = new ArrayList<String>();
124            List<Object> configTurbinePackages =
125                Turbine.getConfiguration()
126                        .getList(TurbineConstants.MODULE_PACKAGES);
127            for (Object o : configTurbinePackages)
128            {
129                turbinePackages.add((String)o);
130            }
131
132            TURBINE_PACKAGES = turbinePackages;
133        }
134
135        List<String> packages = TURBINE_PACKAGES;
136
137        if (!packages.contains(TURBINE_PACKAGE))
138        {
139            packages.add(TURBINE_PACKAGE);
140        }
141
142        return packages;
143    }
144
145    /**
146     * Pulls out an instance of the object by name.  Name is just the
147     * single name of the object.
148     *
149     * @param type Type of the assembler.
150     * @param name Name of object instance.
151     * @return A Screen with the specified name, or null.
152     * @throws Exception a generic exception.
153     */
154    protected T getAssembler(Class<T> type, String name)
155        throws Exception
156    {
157        T asm = null;
158
159        try
160        {
161            if (ab != null)
162            {
163                // Attempt to load the assembler
164                asm = ab.getAssembler(type, name);
165            }
166        }
167        catch (ClassCastException cce)
168        {
169            // This can alternatively let this exception be thrown
170            // So that the ClassCastException is shown in the
171            // browser window.  Like this it shows "Screen not Found"
172            asm = null;
173        }
174
175        if (asm == null)
176        {
177            // If we did not find a screen we should try and give
178            // the user a reason for that...
179            // FIX ME: The AssemblerFactories should each add it's
180            // own string here...
181            List<String> packages = GenericLoader.getPackages();
182
183            throw new ClassNotFoundException(
184                    "\n\n\tRequested " + type + " not found: " + name +
185                    "\n\tTurbine looked in the following " +
186                    "modules.packages path: \n\t" + packages.toString() + "\n");
187        }
188
189        return asm;
190    }
191}