1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18 package org.apache.log4j.or; 19 20 import org.apache.log4j.spi.RendererSupport; 21 import org.apache.log4j.helpers.LogLog; 22 import org.apache.log4j.helpers.Loader; 23 import org.apache.log4j.helpers.OptionConverter; 24 import java.util.Hashtable; 25 26 /** 27 Map class objects to an {@link ObjectRenderer}. 28 29 @author Ceki Gülcü 30 @since version 1.0 */ 31 public class RendererMap { 32 33 Hashtable map; 34 35 static ObjectRenderer defaultRenderer = new DefaultRenderer(); 36 37 public 38 RendererMap() { 39 map = new Hashtable(); 40 } 41 42 /** 43 Add a renderer to a hierarchy passed as parameter. 44 */ 45 static 46 public 47 void addRenderer(RendererSupport repository, String renderedClassName, 48 String renderingClassName) { 49 LogLog.debug("Rendering class: ["+renderingClassName+"], Rendered class: ["+ 50 renderedClassName+"]."); 51 ObjectRenderer renderer = (ObjectRenderer) 52 OptionConverter.instantiateByClassName(renderingClassName, 53 ObjectRenderer.class, 54 null); 55 if(renderer == null) { 56 LogLog.error("Could not instantiate renderer ["+renderingClassName+"]."); 57 return; 58 } else { 59 try { 60 Class renderedClass = Loader.loadClass(renderedClassName); 61 repository.setRenderer(renderedClass, renderer); 62 } catch(ClassNotFoundException e) { 63 LogLog.error("Could not find class ["+renderedClassName+"].", e); 64 } 65 } 66 } 67 68 69 /** 70 Find the appropriate renderer for the class type of the 71 <code>o</code> parameter. This is accomplished by calling the 72 {@link #get(Class)} method. Once a renderer is found, it is 73 applied on the object <code>o</code> and the result is returned 74 as a {@link String}. */ 75 public 76 String findAndRender(Object o) { 77 if(o == null) 78 return null; 79 else 80 return get(o.getClass()).doRender(o); 81 } 82 83 84 /** 85 Syntactic sugar method that calls {@link #get(Class)} with the 86 class of the object parameter. */ 87 public 88 ObjectRenderer get(Object o) { 89 if(o == null) 90 return null; 91 else 92 return get(o.getClass()); 93 } 94 95 96 /** 97 Search the parents of <code>clazz</code> for a renderer. The 98 renderer closest in the hierarchy will be returned. If no 99 renderers could be found, then the default renderer is returned. 100 101 <p>The search first looks for a renderer configured for 102 <code>clazz</code>. If a renderer could not be found, then the 103 search continues by looking at all the interfaces implemented by 104 <code>clazz</code> including the super-interfaces of each 105 interface. If a renderer cannot be found, then the search looks 106 for a renderer defined for the parent (superclass) of 107 <code>clazz</code>. If that fails, then all the interfaces 108 implemented by the parent of <code>clazz</code> are searched and 109 so on. 110 111 <p>For example, if A0, A1, A2 are classes and X0, X1, X2, Y0, Y1 112 are interfaces where A2 extends A1 which in turn extends A0 and 113 similarly X2 extends X1 which extends X0 and Y1 extends Y0. Let 114 us also assume that A1 implements the Y0 interface and that A2 115 implements the X2 interface. 116 117 <p>The table below shows the results returned by the 118 <code>get(A2.class)</code> method depending on the renderers 119 added to the map. 120 121 <p><table border="1"> 122 <tr><th>Added renderers</th><th>Value returned by <code>get(A2.class)</code></th> 123 124 <tr><td><code>A0Renderer</code> 125 <td align="center"><code>A0Renderer</code> 126 127 <tr><td><code>A0Renderer, A1Renderer</code> 128 <td align="center"><code>A1Renderer</code> 129 130 <tr><td><code>X0Renderer</code> 131 <td align="center"><code>X0Renderer</code> 132 133 <tr><td><code>A1Renderer, X0Renderer</code> 134 <td align="center"><code>X0Renderer</code> 135 136 </table> 137 138 <p>This search algorithm is not the most natural, although it is 139 particularly easy to implement. Future log4j versions 140 <em>may</em> implement a more intuitive search 141 algorithm. However, the present algorithm should be acceptable in 142 the vast majority of circumstances. 143 144 */ 145 public 146 ObjectRenderer get(Class clazz) { 147 //System.out.println("\nget: "+clazz); 148 ObjectRenderer r = null; 149 for(Class c = clazz; c != null; c = c.getSuperclass()) { 150 //System.out.println("Searching for class: "+c); 151 r = (ObjectRenderer) map.get(c); 152 if(r != null) { 153 return r; 154 } 155 r = searchInterfaces(c); 156 if(r != null) 157 return r; 158 } 159 return defaultRenderer; 160 } 161 162 ObjectRenderer searchInterfaces(Class c) { 163 //System.out.println("Searching interfaces of class: "+c); 164 165 ObjectRenderer r = (ObjectRenderer) map.get(c); 166 if(r != null) { 167 return r; 168 } else { 169 Class[] ia = c.getInterfaces(); 170 for(int i = 0; i < ia.length; i++) { 171 r = searchInterfaces(ia[i]); 172 if(r != null) 173 return r; 174 } 175 } 176 return null; 177 } 178 179 180 public 181 ObjectRenderer getDefaultRenderer() { 182 return defaultRenderer; 183 } 184 185 186 public 187 void clear() { 188 map.clear(); 189 } 190 191 /** 192 Register an {@link ObjectRenderer} for <code>clazz</code>. 193 */ 194 public 195 void put(Class clazz, ObjectRenderer or) { 196 map.put(clazz, or); 197 } 198 }