001 package org.apache.turbine.services.assemblerbroker.util.java;
002
003
004 /*
005 * Licensed to the Apache Software Foundation (ASF) under one
006 * or more contributor license agreements. See the NOTICE file
007 * distributed with this work for additional information
008 * regarding copyright ownership. The ASF licenses this file
009 * to you under the Apache License, Version 2.0 (the
010 * "License"); you may not use this file except in compliance
011 * with the License. You may obtain a copy of the License at
012 *
013 * http://www.apache.org/licenses/LICENSE-2.0
014 *
015 * Unless required by applicable law or agreed to in writing,
016 * software distributed under the License is distributed on an
017 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
018 * KIND, either express or implied. See the License for the
019 * specific language governing permissions and limitations
020 * under the License.
021 */
022
023 import java.util.Collections;
024 import java.util.HashMap;
025 import java.util.List;
026 import java.util.Map;
027
028 import org.apache.commons.lang.StringUtils;
029 import org.apache.commons.logging.Log;
030 import org.apache.commons.logging.LogFactory;
031 import org.apache.turbine.modules.Assembler;
032 import org.apache.turbine.modules.GenericLoader;
033 import org.apache.turbine.modules.Loader;
034 import org.apache.turbine.services.assemblerbroker.util.AssemblerFactory;
035
036 /**
037 * A screen factory that attempts to load a java class from
038 * the module packages defined in the TurbineResource.properties.
039 *
040 * @author <a href="mailto:leon@opticode.co.za">Leon Messerschmidt</a>
041 * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
042 * @version $Id: JavaBaseFactory.java 1078552 2011-03-06 19:58:46Z tv $
043 */
044 public abstract class JavaBaseFactory<T extends Assembler>
045 implements AssemblerFactory<T>
046 {
047 /** A vector of packages. */
048 private static List<String> packages = GenericLoader.getPackages();
049
050 /** Logging */
051 protected Log log = LogFactory.getLog(this.getClass());
052
053 /**
054 * A cache for previously obtained Class instances, which we keep in order
055 * to reduce the Class.forName() overhead (which can be sizable).
056 */
057 private final Map<String, Class<T>> classCache =
058 Collections.synchronizedMap(new HashMap<String, Class<T>>());
059
060 /**
061 * Get an Assembler.
062 *
063 * @param packageName java package name
064 * @param name name of the requested Assembler
065 * @return an Assembler
066 */
067 @SuppressWarnings("unchecked")
068 public T getAssembler(String packageName, String name)
069 {
070 T assembler = null;
071
072 log.debug("Class Fragment is " + name);
073
074 if (StringUtils.isNotEmpty(name))
075 {
076 for (String p : packages)
077 {
078 StringBuffer sb = new StringBuffer();
079
080 sb.append(p).append('.').append(packageName).append('.').append(name);
081
082 String className = sb.toString();
083
084 log.debug("Trying " + className);
085
086 try
087 {
088 Class<T> servClass = classCache.get(className);
089 if(servClass == null)
090 {
091 servClass = (Class<T>) Class.forName(className.toString());
092 classCache.put(className, servClass);
093 }
094 assembler = servClass.newInstance();
095 break; // for()
096 }
097 catch (ClassNotFoundException cnfe)
098 {
099 // 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 }