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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.List;
23  
24  import org.apache.turbine.Turbine;
25  import org.apache.turbine.TurbineConstants;
26  import org.apache.turbine.pipeline.PipelineData;
27  import org.apache.turbine.services.assemblerbroker.AssemblerBrokerService;
28  import org.apache.turbine.services.assemblerbroker.TurbineAssemblerBroker;
29  import org.apache.turbine.util.RunData;
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   * @version $Id: GenericLoader.java 1078552 2011-03-06 19:58:46Z tv $
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       * Should revert to abstract when RunData has gone.
67       * @exception Exception a generic exception.
68       */
69      public void exec(PipelineData pipelineData, String name)
70              throws Exception
71      {
72          RunData data = getRunData(pipelineData);
73          exec(data, name);
74      }
75  
76  
77      /**
78       * Attempts to load and execute the external action that has been
79       * set.
80       * @deprecated Use of this method should be avoided. Use
81       * <code>exec(PipelineData data, String name)</code> instead.
82       * @exception Exception a generic exception.
83       */
84      @Deprecated
85      public abstract void exec(RunData data, String name)
86      	throws Exception;
87  
88      /**
89       * Commented out.
90       * This method should return the complete classpath + name.
91       *
92       * @param name
93       * @return
94       *
95       public abstract String getClassName(String name);
96       */
97  
98      /**
99       * Returns whether or not this external action is reload itself.
100      * This is in cases where the Next button would be clicked, but
101      * since we are checking for that, we would go into an endless
102      * loop.
103      *
104      * @return True if the action is reload.
105      */
106     public boolean reload()
107     {
108         return this.reload;
109     }
110 
111     /**
112      * Sets whether or not this external action is reload itself.
113      * This is in cases where the Next button would be clicked, but
114      * since we are checking for that, we would go into an endless
115      * loop.
116      *
117      * @param reload True if the action must be marked as reload.
118      * @return Itself.
119      */
120     public GenericLoader setReload(boolean reload)
121     {
122         this.reload = reload;
123         return this;
124     }
125 
126     /**
127      * Gets the base package where Turbine should find its default
128      * modules.
129      *
130      * @return A String with the base package name.
131      */
132     public static String getBasePackage()
133     {
134         return TURBINE_PACKAGE;
135     }
136 
137     /**
138      * Gets the package list where Turbine should find its
139      * modules.
140      *
141      * @return A List with the package names (including the base package).
142      */
143     @SuppressWarnings("unchecked")
144     public static List<String> getPackages()
145     {
146         if (TURBINE_PACKAGES == null)
147         {
148             TURBINE_PACKAGES =
149                 Turbine.getConfiguration().getList(TurbineConstants.MODULE_PACKAGES);
150         }
151 
152         List<String> packages = TURBINE_PACKAGES;
153 
154         if (!packages.contains(TURBINE_PACKAGE))
155         {
156             packages.add(TURBINE_PACKAGE);
157         }
158 
159         return packages;
160     }
161 
162     /**
163      * Pulls out an instance of the object by name.  Name is just the
164      * single name of the object.
165      *
166      * @param type Type of the assembler.
167      * @param name Name of object instance.
168      * @return A Screen with the specified name, or null.
169      * @exception Exception a generic exception.
170      */
171     protected T getAssembler(String type, String name)
172         throws Exception
173     {
174         T asm = null;
175 
176         try
177         {
178             if (ab != null)
179             {
180                 // Attempt to load the assembler
181                 asm = (T) ab.getAssembler(type, name);
182             }
183         }
184         catch (ClassCastException cce)
185         {
186             // This can alternatively let this exception be thrown
187             // So that the ClassCastException is shown in the
188             // browser window.  Like this it shows "Screen not Found"
189             asm = null;
190         }
191 
192         if (asm == null)
193         {
194             // If we did not find a screen we should try and give
195             // the user a reason for that...
196             // FIX ME: The AssemblerFactories should each add it's
197             // own string here...
198             List<String> packages = GenericLoader.getPackages();
199 
200             throw new ClassNotFoundException(
201                     "\n\n\tRequested " + type + " not found: " + name +
202                     "\n\tTurbine looked in the following " +
203                     "modules.packages path: \n\t" + packages.toString() + "\n");
204         }
205 
206         return asm;
207     }
208 
209     /**
210      * Helper method to cast from PipelineData to RunData. This will go when
211      * the pipeline is fully implemented and the RunData-methods are removed
212      *
213      * @param pipelineData a PipelineData object
214      *
215      * @return the input object casted to RunData
216      */
217     private RunData getRunData(PipelineData pipelineData)
218     {
219         if(!(pipelineData instanceof RunData))
220         {
221             throw new RuntimeException("Can't cast to rundata from pipeline data.");
222         }
223         return (RunData)pipelineData;
224     }
225 }