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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 }