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1   package org.apache.turbine.services.assemblerbroker.util.java;
2   
3   
4   /*
5    * Licensed to the Apache Software Foundation (ASF) under one
6    * or more contributor license agreements.  See the NOTICE file
7    * distributed with this work for additional information
8    * regarding copyright ownership.  The ASF licenses this file
9    * to you under the Apache License, Version 2.0 (the
10   * "License"); you may not use this file except in compliance
11   * with the License.  You may obtain a copy of the License at
12   *
13   *   http://www.apache.org/licenses/LICENSE-2.0
14   *
15   * Unless required by applicable law or agreed to in writing,
16   * software distributed under the License is distributed on an
17   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
18   * KIND, either express or implied.  See the License for the
19   * specific language governing permissions and limitations
20   * under the License.
21   */
22  
23  import java.util.Collections;
24  import java.util.HashMap;
25  import java.util.List;
26  import java.util.Map;
27  
28  import org.apache.commons.lang.StringUtils;
29  import org.apache.commons.logging.Log;
30  import org.apache.commons.logging.LogFactory;
31  import org.apache.turbine.modules.Assembler;
32  import org.apache.turbine.modules.GenericLoader;
33  import org.apache.turbine.modules.Loader;
34  import org.apache.turbine.services.assemblerbroker.util.AssemblerFactory;
35  
36  /**
37   * A screen factory that attempts to load a java class from
38   * the module packages defined in the TurbineResource.properties.
39   *
40   * @author <a href="mailto:leon@opticode.co.za">Leon Messerschmidt</a>
41   * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
42   * @version $Id: JavaBaseFactory.java 1078552 2011-03-06 19:58:46Z tv $
43   */
44  public abstract class JavaBaseFactory<T extends Assembler>
45      implements AssemblerFactory<T>
46  {
47      /** A vector of packages. */
48      private static List<String> packages = GenericLoader.getPackages();
49  
50      /** Logging */
51      protected Log log = LogFactory.getLog(this.getClass());
52  
53      /**
54       * A cache for previously obtained Class instances, which we keep in order
55       * to reduce the Class.forName() overhead (which can be sizable).
56       */
57      private final Map<String, Class<T>> classCache =
58      	Collections.synchronizedMap(new HashMap<String, Class<T>>());
59  
60      /**
61       * Get an Assembler.
62       *
63       * @param packageName java package name
64       * @param name name of the requested Assembler
65       * @return an Assembler
66       */
67      @SuppressWarnings("unchecked")
68      public T getAssembler(String packageName, String name)
69      {
70          T assembler = null;
71  
72          log.debug("Class Fragment is " + name);
73  
74          if (StringUtils.isNotEmpty(name))
75          {
76              for (String p : packages)
77              {
78                  StringBuffer sb = new StringBuffer();
79  
80                  sb.append(p).append('.').append(packageName).append('.').append(name);
81  
82                  String className = sb.toString();
83  
84                  log.debug("Trying " + className);
85  
86                  try
87                  {
88                      Class<T> servClass = classCache.get(className);
89                      if(servClass == null)
90                      {
91                          servClass = (Class<T>) Class.forName(className.toString());
92                          classCache.put(className, servClass);
93                      }
94                      assembler = servClass.newInstance();
95                      break; // for()
96                  }
97                  catch (ClassNotFoundException cnfe)
98                  {
99                      // Do this so we loop through all the packages.
100                     log.debug(className + ": Not found");
101                 }
102                 catch (NoClassDefFoundError ncdfe)
103                 {
104                     // Do this so we loop through all the packages.
105                     log.debug(className + ": No Class Definition found");
106                 }
107                 catch (ClassCastException cce)
108                 {
109                     // This means trouble!
110                     // Alternatively we can throw this exception so
111                     // that it will appear on the client browser
112                     log.error("Could not load "+className, cce);
113                     break; // for()
114                 }
115                 catch (InstantiationException ine)
116                 {
117                     // This means trouble!
118                     // Alternatively we can throw this exception so
119                     // that it will appear on the client browser
120                     log.error("Could not load "+className, ine);
121                     break; // for()
122                 }
123                 catch (IllegalAccessException ilae)
124                 {
125                     // This means trouble!
126                     // Alternatively we can throw this exception so
127                     // that it will appear on the client browser
128                     log.error("Could not load "+className, ilae);
129                     break; // for()
130                 }
131                 // With ClassCastException, InstantiationException we hit big problems
132             }
133         }
134         log.debug("Returning: " + assembler);
135 
136         return assembler;
137     }
138 
139     /**
140      * Get the loader for this type of assembler
141      *
142      * @return a Loader
143      */
144     public abstract Loader<T> getLoader();
145 
146     /**
147      * Get the size of a possibly configured cache
148      *
149      * @return the size of the cache in bytes
150      */
151     public int getCacheSize()
152     {
153         return getLoader().getCacheSize();
154     }
155 }