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 }