001package 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 023import java.util.List; 024import java.util.concurrent.ConcurrentHashMap; 025 026import org.apache.commons.lang.StringUtils; 027import org.apache.commons.logging.Log; 028import org.apache.commons.logging.LogFactory; 029import org.apache.turbine.modules.Assembler; 030import org.apache.turbine.modules.GenericLoader; 031import org.apache.turbine.modules.Loader; 032import org.apache.turbine.services.assemblerbroker.util.AssemblerFactory; 033 034/** 035 * A screen factory that attempts to load a java class from 036 * the module packages defined in the TurbineResource.properties. 037 * 038 * @author <a href="mailto:leon@opticode.co.za">Leon Messerschmidt</a> 039 * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a> 040 * @param <T> the specialized assembler type 041 */ 042public abstract class JavaBaseFactory<T extends Assembler> 043 implements AssemblerFactory<T> 044{ 045 /** A vector of packages. */ 046 private static List<String> packages = GenericLoader.getPackages(); 047 048 /** Logging */ 049 protected Log log = LogFactory.getLog(this.getClass()); 050 051 /** 052 * A cache for previously obtained Class instances, which we keep in order 053 * to reduce the Class.forName() overhead (which can be sizable). 054 */ 055 private final ConcurrentHashMap<String, Class<T>> classCache = new ConcurrentHashMap<String, Class<T>>(); 056 057 /** 058 * Get an Assembler. 059 * 060 * @param packageName java package name 061 * @param name name of the requested Assembler 062 * @return an Assembler 063 */ 064 @SuppressWarnings("unchecked") 065 public T getAssembler(String packageName, String name) 066 { 067 T assembler = null; 068 069 if (log.isDebugEnabled()) 070 { 071 log.debug("Class Fragment is " + name); 072 } 073 074 if (StringUtils.isNotEmpty(name)) 075 { 076 for (String p : packages) 077 { 078 StringBuilder sb = new StringBuilder(); 079 080 sb.append(p).append('.').append(packageName).append('.').append(name); 081 String className = sb.toString(); 082 083 if (log.isDebugEnabled()) 084 { 085 log.debug("Trying " + className); 086 } 087 088 try 089 { 090 Class<T> servClass = classCache.get(className); 091 if (servClass == null) 092 { 093 servClass = (Class<T>) Class.forName(className); 094 Class<T> _servClass = classCache.putIfAbsent(className, servClass); 095 if (_servClass != null) 096 { 097 servClass = _servClass; 098 } 099 } 100 assembler = servClass.newInstance(); 101 break; // for() 102 } 103 catch (ClassNotFoundException cnfe) 104 { 105 // Do this so we loop through all the packages. 106 log.debug(className + ": Not found"); 107 } 108 catch (NoClassDefFoundError ncdfe) 109 { 110 // Do this so we loop through all the packages. 111 log.debug(className + ": No Class Definition found"); 112 } 113 catch (ClassCastException cce) 114 { 115 // This means trouble! 116 // Alternatively we can throw this exception so 117 // that it will appear on the client browser 118 log.error("Could not load "+className, cce); 119 break; // for() 120 } 121 catch (InstantiationException ine) 122 { 123 // This means trouble! 124 // Alternatively we can throw this exception so 125 // that it will appear on the client browser 126 log.error("Could not load "+className, ine); 127 break; // for() 128 } 129 catch (IllegalAccessException ilae) 130 { 131 // This means trouble! 132 // Alternatively we can throw this exception so 133 // that it will appear on the client browser 134 log.error("Could not load "+className, ilae); 135 break; // for() 136 } 137 // With ClassCastException, InstantiationException we hit big problems 138 } 139 } 140 141 if (log.isDebugEnabled()) 142 { 143 log.debug("Returning: " + assembler); 144 } 145 146 return assembler; 147 } 148 149 /** 150 * Get the loader for this type of assembler 151 * 152 * @return a Loader 153 */ 154 @Override 155 public abstract Loader<T> getLoader(); 156 157 /** 158 * Get the size of a possibly configured cache 159 * 160 * @return the size of the cache in bytes 161 */ 162 @Override 163 public int getCacheSize() 164 { 165 return getLoader().getCacheSize(); 166 } 167}