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    1   package org.apache.turbine.modules;
    2
    3   /*
    4    * Licensed to the Apache Software Foundation (ASF) under one
    5    * or more contributor license agreements.  See the NOTICE file
    6    * distributed with this work for additional information
    7    * regarding copyright ownership.  The ASF licenses this file
    8    * to you under the Apache License, Version 2.0 (the
    9    * "License"); you may not use this file except in compliance
    10   * with the License.  You may obtain a copy of the License at
    11   *
    12   *   http://www.apache.org/licenses/LICENSE-2.0
    13   *
    14   * Unless required by applicable law or agreed to in writing,
    15   * software distributed under the License is distributed on an
    16   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    17   * KIND, either express or implied.  See the License for the
    18   * specific language governing permissions and limitations
    19   * under the License.
    20   */
    21
    22  import java.util.ArrayList;
    23  import java.util.List;
    24
    25  import org.apache.turbine.Turbine;
    26  import org.apache.turbine.TurbineConstants;
    27  import org.apache.turbine.pipeline.PipelineData;
    28  import org.apache.turbine.services.assemblerbroker.AssemblerBrokerService;
    29  import org.apache.turbine.services.assemblerbroker.TurbineAssemblerBroker;
    30
    31  /**
    32   * This is the base class for the loaders. It contains code that is
    33   * used across all of the loaders. It also specifies the interface
    34   * that is required to be called a Loader.
    35   *
    36   * @author <a href="mailto:mbryson@mont.mindspring.com">Dave Bryson</a>
    37   * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
    38   * @author <a href="mailto:peter@courcoux.biz">Peter Courcoux</a>
    39   * @param <T> the specialized assembler type
    40   */
    41  public abstract class GenericLoader<T extends Assembler>
    42  {
    43      /** The Assembler Broker Service */
    44      protected AssemblerBrokerService ab = TurbineAssemblerBroker.getService();
    45
    46      /** @serial This can be serialized */
    47      private boolean reload = false;
    48
    49      /** Base packages path for Turbine */
    50      private static final String TURBINE_PACKAGE = "org.apache.turbine.modules";
    51
    52      /** Packages paths for Turbine */
    53      private static List<String> TURBINE_PACKAGES = null;
    54
    55      /**
    56       * Basic constructor for creating a loader.
    57       */
    58      public GenericLoader()
    59      {
    60          super();
    61      }
    62
    63      /**
    64       * Attempts to load and execute the external action that has been
    65       * set.
    66       * @param pipelineData the Turbine request
    67       * @param name the name of the assembler module
    68       * @exception Exception a generic exception.
    69       */
    70      public abstract void exec(PipelineData pipelineData, String name)
    71              throws Exception;
    72
    73      /**
    74       * Returns whether or not this external action is reload itself.
    75       * This is in cases where the Next button would be clicked, but
    76       * since we are checking for that, we would go into an endless
    77       * loop.
    78       *
    79       * @return True if the action is reload.
    80       */
    81      public boolean reload()
    82      {
    83          return this.reload;
    84      }
    85
    86      /**
    87       * Sets whether or not this external action is reload itself.
    88       * This is in cases where the Next button would be clicked, but
    89       * since we are checking for that, we would go into an endless
    90       * loop.
    91       *
    92       * @param reload True if the action must be marked as reload.
    93       * @return Itself.
    94       */
    95      public GenericLoader<T> setReload(boolean reload)
    96      {
    97          this.reload = reload;
    98          return this;
    99      }
    100
    101     /**
    102      * Gets the base package where Turbine should find its default
    103      * modules.
    104      *
    105      * @return A String with the base package name.
    106      */
    107     public static String getBasePackage()
    108     {
    109         return TURBINE_PACKAGE;
    110     }
    111
    112     /**
    113      * Gets the package list where Turbine should find its
    114      * modules.
    115      *
    116      * @return A List with the package names (including the base package).
    117      */
    118     public static List<String> getPackages()
    119     {
    120         if (TURBINE_PACKAGES == null)
    121         {
    122             List<String> turbinePackages = new ArrayList<String>();
    123             List<Object> configTurbinePackages =
    124                 Turbine.getConfiguration()
    125                 	.getList(TurbineConstants.MODULE_PACKAGES);
    126             for (Object o : configTurbinePackages)
    127             {
    128             	turbinePackages.add((String)o);
    129             }
    130
    131             TURBINE_PACKAGES = turbinePackages;
    132         }
    133
    134         List<String> packages = TURBINE_PACKAGES;
    135
    136         if (!packages.contains(TURBINE_PACKAGE))
    137         {
    138             packages.add(TURBINE_PACKAGE);
    139         }
    140
    141         return packages;
    142     }
    143
    144     /**
    145      * Pulls out an instance of the object by name.  Name is just the
    146      * single name of the object.
    147      *
    148      * @param type Type of the assembler.
    149      * @param name Name of object instance.
    150      * @return A Screen with the specified name, or null.
    151      * @exception Exception a generic exception.
    152      */
    153     protected T getAssembler(Class<T> type, String name)
    154         throws Exception
    155     {
    156         T asm = null;
    157
    158         try
    159         {
    160             if (ab != null)
    161             {
    162                 // Attempt to load the assembler
    163                 asm = ab.getAssembler(type, name);
    164             }
    165         }
    166         catch (ClassCastException cce)
    167         {
    168             // This can alternatively let this exception be thrown
    169             // So that the ClassCastException is shown in the
    170             // browser window.  Like this it shows "Screen not Found"
    171             asm = null;
    172         }
    173
    174         if (asm == null)
    175         {
    176             // If we did not find a screen we should try and give
    177             // the user a reason for that...
    178             // FIX ME: The AssemblerFactories should each add it's
    179             // own string here...
    180             List<String> packages = GenericLoader.getPackages();
    181
    182             throw new ClassNotFoundException(
    183                     "\n\n\tRequested " + type + " not found: " + name +
    184                     "\n\tTurbine looked in the following " +
    185                     "modules.packages path: \n\t" + packages.toString() + "\n");
    186         }
    187
    188         return asm;
    189     }
    190 }