1 package org.apache.commons.digester3.plugins.strategies; 2 3 /* 4 * Licensed to the Apache Software Foundation (ASF) under one 5 * or more contributor license agreements. See the NOTICE file 6 * distributed with this work for additional information 7 * regarding copyright ownership. The ASF licenses this file 8 * to you under the Apache License, Version 2.0 (the 9 * "License"); you may not use this file except in compliance 10 * with the License. You may obtain a copy of the License at 11 * 12 * http://www.apache.org/licenses/LICENSE-2.0 13 * 14 * Unless required by applicable law or agreed to in writing, 15 * software distributed under the License is distributed on an 16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 17 * KIND, either express or implied. See the License for the 18 * specific language governing permissions and limitations 19 * under the License. 20 */ 21 22 import java.io.IOException; 23 import java.io.InputStream; 24 import java.util.Properties; 25 26 import org.apache.commons.digester3.Digester; 27 import org.apache.commons.digester3.plugins.PluginException; 28 import org.apache.commons.digester3.plugins.RuleFinder; 29 import org.apache.commons.digester3.plugins.RuleLoader; 30 31 /** 32 * A rule-finding algorithm which expects the user to specify a resource name (ie a file in the classpath). The file is 33 * expected to contain Digester rules in xmlrules format. 34 * 35 * @since 1.6 36 */ 37 public class FinderFromResource 38 extends RuleFinder 39 { 40 41 /** 42 * Default name of xml attribute on the plugin declaration which is used to configure rule-loading 43 * for that declaration. 44 */ 45 private static final String DFLT_RESOURCE_ATTR = "resource"; 46 47 /** See {@link #findLoader}. */ 48 private final String resourceAttr; 49 50 /** Constructor. */ 51 public FinderFromResource() 52 { 53 this( DFLT_RESOURCE_ATTR ); 54 } 55 56 /** 57 * See {@link #findLoader}. 58 * 59 * @param resourceAttr Name of xml attribute on the plugin declaration which is used to configure rule-loading 60 * for that declaration 61 */ 62 public FinderFromResource( String resourceAttr ) 63 { 64 this.resourceAttr = resourceAttr; 65 } 66 67 /** 68 * If there exists a property with the name matching constructor param resourceAttr, then load that file, run it 69 * through the xmlrules module and return an object encapsulating those rules. 70 * <p> 71 * If there is no matching property provided, then just return null. 72 * <p> 73 * The returned object (when non-null) will add the selected rules to the digester whenever its addRules method is 74 * invoked. 75 * 76 * @param d The digester instance where locating plugin classes 77 * @param pluginClass The plugin Java class 78 * @param p The properties object that holds any xml attributes the user may have specified on the plugin 79 * declaration in order to indicate how to locate the plugin rules. 80 * @return a source of digester rules for the specified plugin class. 81 * @throws PluginException if the algorithm finds a source of rules, but there is something invalid 82 * about that source. 83 */ 84 @Override 85 public RuleLoader findLoader( Digester d, Class<?> pluginClass, Properties p ) 86 throws PluginException 87 { 88 String resourceName = p.getProperty( resourceAttr ); 89 if ( resourceName == null ) 90 { 91 // nope, user hasn't requested dynamic rules to be loaded 92 // from a specific file. 93 return null; 94 } 95 96 InputStream is = pluginClass.getClassLoader().getResourceAsStream( resourceName ); 97 98 if ( is == null ) 99 { 100 throw new PluginException( "Resource " + resourceName + " not found." ); 101 } 102 103 return loadRules( d, pluginClass, is, resourceName ); 104 } 105 106 /** 107 * Open the specified resource file (ie a file in the classpath, including being within a jar in the classpath), run 108 * it through the xmlrules module and return an object encapsulating those rules. 109 * 110 * @param d is the digester into which rules will eventually be loaded. 111 * @param pluginClass is the class whose xml params the rules are parsing. 112 * @param is is where the xmlrules will be read from, and must be non-null. 113 * @param resourceName is a string describing the source of the xmlrules, for use in generating error messages. 114 * @return a source of digester rules for the specified plugin class. 115 * @throws PluginException if any error occurs 116 */ 117 public static RuleLoader loadRules( Digester d, Class<?> pluginClass, InputStream is, String resourceName ) 118 throws PluginException 119 { 120 try 121 { 122 RuleLoader loader = new LoaderFromStream( is ); 123 return loader; 124 } 125 catch ( Exception e ) 126 { 127 throw new PluginException( "Unable to load xmlrules from resource [" + resourceName + "]", e ); 128 } 129 finally 130 { 131 try 132 { 133 is.close(); 134 } 135 catch ( IOException ioe ) 136 { 137 throw new PluginException( "Unable to close stream for resource [" + resourceName + "]", ioe ); 138 } 139 } 140 } 141 142 }