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org.apache.commons.jelly.impl.DefaultTagLibraryResolver |
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1 | /* |
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2 | * Copyright 2002,2004 The Apache Software Foundation. |
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3 | * |
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4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
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5 | * you may not use this file except in compliance with the License. |
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6 | * You may obtain a copy of the License at |
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7 | * |
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8 | * http://www.apache.org/licenses/LICENSE-2.0 |
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9 | * |
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10 | * Unless required by applicable law or agreed to in writing, software |
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11 | * distributed under the License is distributed on an "AS IS" BASIS, |
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12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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13 | * See the License for the specific language governing permissions and |
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14 | * limitations under the License. |
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15 | */ |
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16 | package org.apache.commons.jelly.impl; |
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17 | ||
18 | import org.apache.commons.discovery.ResourceClass; |
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19 | import org.apache.commons.discovery.ResourceClassIterator; |
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20 | import org.apache.commons.discovery.resource.ClassLoaders; |
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21 | import org.apache.commons.discovery.resource.classes.DiscoverClasses; |
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22 | import org.apache.commons.jelly.TagLibrary; |
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23 | import org.apache.commons.jelly.util.ClassLoaderUtils; |
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24 | import org.apache.commons.logging.Log; |
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25 | import org.apache.commons.logging.LogFactory; |
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26 | ||
27 | ||
28 | /** |
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29 | * <p><code>DefaultTagLibraryResolver</code> is a default implemenation |
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30 | * which attempts to interpret the URI as a String called 'jelly:className' |
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31 | * and class load the given Java class. Otherwise META-INF/services/jelly/uri |
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32 | * is searched for on the thread context's class path and, if found, that |
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33 | * class will be loaded.</p> |
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34 | * |
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35 | * @author <a href="mailto:jstrachan@apache.org">James Strachan</a> |
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36 | * @version $Revision: 155420 $ |
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37 | */ |
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38 | public class DefaultTagLibraryResolver implements TagLibraryResolver { |
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39 | ||
40 | /** The Log to which logging calls will be made. */ |
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41 | 0 | private static final Log log = LogFactory.getLog(DefaultTagLibraryResolver.class); |
42 | ||
43 | private DiscoverClasses discovery; |
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44 | ||
45 | /** |
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46 | * The class loader to use for instantiating application objects. |
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47 | * If not specified, the context class loader, or the class loader |
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48 | * used to load this class itself, is used, based on the value of the |
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49 | * <code>useContextClassLoader</code> variable. |
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50 | */ |
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51 | private ClassLoader classLoader; |
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52 | ||
53 | /** |
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54 | * Do we want to use the Context ClassLoader when loading classes |
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55 | * for instantiating new objects? Default is <code>false</code>. |
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56 | */ |
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57 | 0 | private boolean useContextClassLoader = false; |
58 | ||
59 | ||
60 | 0 | public DefaultTagLibraryResolver() { |
61 | 0 | } |
62 | ||
63 | ||
64 | // TagLibraryResolver interface |
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65 | //------------------------------------------------------------------------- |
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66 | ||
67 | /** |
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68 | * Attempts to resolve the given URI to be associated with a TagLibrary |
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69 | * otherwise null is returned to indicate no tag library could be found |
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70 | * so that the namespace URI should be treated as just vanilla XML. |
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71 | */ |
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72 | public TagLibrary resolveTagLibrary(String uri) { |
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73 | 0 | DiscoverClasses discovery = getDiscoverClasses(); |
74 | 0 | String name = uri; |
75 | 0 | if ( uri.startsWith( "jelly:" ) ) { |
76 | 0 | name = "jelly." + uri.substring(6); |
77 | } |
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78 | ||
79 | 0 | log.info( "Looking up service name: " + name ); |
80 | ||
81 | /* |
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82 | ClassLoaders loaders = ClassLoaders.getAppLoaders(TagLibrary.class, getClass(), false); |
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83 | ||
84 | DiscoverClass discover = new DiscoverClass(loaders); |
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85 | Class implClass = discover.find(TestInterface2.class); |
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86 | ||
87 | ||
88 | ||
89 | TagLibrary answer = null; |
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90 | try { |
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91 | answer = (TagLibrary) DiscoverSingleton.find(TagLibrary.class, name); |
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92 | } |
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93 | catch (Exception e) { |
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94 | log.error( "Could not load service: " + name ); |
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95 | } |
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96 | return answer; |
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97 | */ |
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98 | 0 | ResourceClassIterator iter = discovery.findResourceClasses(name); |
99 | 0 | while (iter.hasNext()) { |
100 | 0 | ResourceClass resource = iter.nextResourceClass(); |
101 | try { |
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102 | 0 | Class typeClass = resource.loadClass(); |
103 | 0 | if ( typeClass != null ) { |
104 | 0 | return newInstance(uri, typeClass); |
105 | } |
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106 | } |
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107 | 0 | catch (Exception e) { |
108 | 0 | log.error( "Could not load service: " + resource ); |
109 | 0 | } |
110 | 0 | } |
111 | 0 | log.info( "Could not find any services for name: " + name ); |
112 | 0 | return null; |
113 | } |
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114 | ||
115 | // Properties |
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116 | //------------------------------------------------------------------------- |
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117 | ||
118 | /** |
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119 | * Return the class loader to be used for instantiating application objects |
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120 | * when required. This is determined based upon the following rules: |
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121 | * <ul> |
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122 | * <li>The class loader set by <code>setClassLoader()</code>, if any</li> |
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123 | * <li>The thread context class loader, if it exists and the |
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124 | * <code>useContextClassLoader</code> property is set to true</li> |
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125 | * <li>The class loader used to load the XMLParser class itself. |
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126 | * </ul> |
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127 | */ |
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128 | public ClassLoader getClassLoader() { |
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129 | 0 | return ClassLoaderUtils.getClassLoader(classLoader, useContextClassLoader, getClass()); |
130 | } |
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131 | ||
132 | /** |
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133 | * Set the class loader to be used for instantiating application objects |
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134 | * when required. |
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135 | * |
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136 | * @param classLoader The new class loader to use, or <code>null</code> |
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137 | * to revert to the standard rules |
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138 | */ |
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139 | public void setClassLoader(ClassLoader classLoader) { |
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140 | 0 | this.classLoader = classLoader; |
141 | 0 | } |
142 | ||
143 | /** |
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144 | * Return the boolean as to whether the context classloader should be used. |
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145 | */ |
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146 | public boolean getUseContextClassLoader() { |
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147 | 0 | return useContextClassLoader; |
148 | } |
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149 | ||
150 | /** |
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151 | * Determine whether to use the Context ClassLoader (the one found by |
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152 | * calling <code>Thread.currentThread().getContextClassLoader()</code>) |
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153 | * to resolve/load classes. If not |
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154 | * using Context ClassLoader, then the class-loading defaults to |
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155 | * using the calling-class' ClassLoader. |
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156 | * |
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157 | * @param boolean determines whether to use JellyContext ClassLoader. |
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158 | */ |
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159 | public void setUseContextClassLoader(boolean use) { |
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160 | 0 | useContextClassLoader = use; |
161 | 0 | } |
162 | ||
163 | /** |
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164 | * @return the DiscoverClasses instance to use to locate services. |
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165 | * This object is lazily created if it has not been configured. |
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166 | */ |
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167 | public DiscoverClasses getDiscoverClasses() { |
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168 | 0 | if ( discovery == null ) { |
169 | 0 | ClassLoaders loaders = ClassLoaders.getAppLoaders(TagLibrary.class, getClass(), false); |
170 | 0 | discovery = new DiscoverClasses(loaders); |
171 | } |
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172 | 0 | return discovery; |
173 | } |
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174 | ||
175 | /** |
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176 | * Sets the fully configured DiscoverClasses instance to be used to |
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177 | * lookup services |
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178 | */ |
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179 | public void setDiscoverClasses(DiscoverClasses discovery) { |
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180 | 0 | this.discovery = discovery; |
181 | 0 | } |
182 | ||
183 | // Implementation methods |
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184 | //------------------------------------------------------------------------- |
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185 | ||
186 | /** |
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187 | * Instantiates the given class name. Otherwise an exception is logged |
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188 | * and null is returned |
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189 | */ |
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190 | protected TagLibrary loadClass(String uri, String className) { |
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191 | try { |
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192 | 0 | Class theClass = getClassLoader().loadClass(className); |
193 | 0 | if ( theClass != null ) { |
194 | 0 | return newInstance(uri, theClass); |
195 | } |
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196 | } |
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197 | 0 | catch (ClassNotFoundException e) { |
198 | 0 | log.error("Could not find the class: " + className + " when trying to resolve URI: " + uri, e); |
199 | 0 | } |
200 | 0 | return null; |
201 | } |
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202 | ||
203 | ||
204 | /** |
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205 | * Creates a new instance of the given TagLibrary class or |
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206 | * return null if it could not be instantiated. |
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207 | */ |
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208 | protected TagLibrary newInstance(String uri, Class theClass) { |
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209 | try { |
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210 | 0 | Object object = theClass.newInstance(); |
211 | 0 | if (object instanceof TagLibrary) { |
212 | 0 | return (TagLibrary) object; |
213 | } |
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214 | else { |
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215 | 0 | log.error( |
216 | "The tag library object mapped to: " |
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217 | + uri |
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218 | + " is not a TagLibrary. Object = " |
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219 | + object); |
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220 | } |
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221 | } |
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222 | 0 | catch (Exception e) { |
223 | 0 | log.error( |
224 | "Could not instantiate instance of class: " + theClass.getName() + ". Reason: " + e, |
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225 | e); |
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226 | 0 | } |
227 | 0 | return null; |
228 | } |
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229 | ||
230 | } |
This report is generated by jcoverage, Maven and Maven JCoverage Plugin. |