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.FileInputStream; 23 import java.io.IOException; 24 import java.io.InputStream; 25 import java.util.Properties; 26 27 import org.apache.commons.digester3.Digester; 28 import org.apache.commons.digester3.plugins.PluginException; 29 import org.apache.commons.digester3.plugins.RuleFinder; 30 import org.apache.commons.digester3.plugins.RuleLoader; 31 32 /** 33 * A rule-finding algorithm which expects the user to specify an absolute or relative path in the plugin declaration. 34 * <p> 35 * The file is expected to contain Digester rules in xmlrules format. 36 * 37 * @since 1.6 38 */ 39 public class FinderFromFile 40 extends RuleFinder 41 { 42 43 /** 44 * The default XML attribute that needs to be present on a plugin declaration in order to specify the file to 45 * load rules from. 46 */ 47 private static final String DFLT_FILENAME_ATTR = "file"; 48 49 /** See {@link #findLoader}. */ 50 private final String filenameAttr; 51 52 /** See {@link #findLoader}. */ 53 public FinderFromFile() 54 { 55 this( DFLT_FILENAME_ATTR ); 56 } 57 58 /** 59 * See {@link #findLoader}. 60 * 61 * @param filenameAttr the XML attribute that needs to be present on a plugin declaration in order to specify the 62 * file to load rules from. 63 */ 64 public FinderFromFile( String filenameAttr ) 65 { 66 this.filenameAttr = filenameAttr; 67 } 68 69 /** 70 * If there exists a property with the name specified in the constructor, then load that file, run it through the 71 * xmlrules module and return an object encapsulating those rules. 72 * <p> 73 * If there is no matching property provided, then just return null. 74 * <p> 75 * The returned object (when non-null) will add the selected rules to the digester whenever its addRules method is 76 * invoked. 77 * 78 * @param d The digester instance where locating plugin classes 79 * @param pluginClass The plugin Java class 80 * @param p The properties object that holds any xml attributes the user may have specified on the plugin 81 * declaration in order to indicate how to locate the plugin rules. 82 * @return a source of digester rules for the specified plugin class. 83 * @throws PluginException if the algorithm finds a source of rules, but there is something invalid 84 * about that source. 85 */ 86 @Override 87 public RuleLoader findLoader( Digester d, Class<?> pluginClass, Properties p ) 88 throws PluginException 89 { 90 91 String rulesFileName = p.getProperty( filenameAttr ); 92 if ( rulesFileName == null ) 93 { 94 // nope, user hasn't requested dynamic rules to be loaded 95 // from a specific file. 96 return null; 97 } 98 99 InputStream is = null; 100 try 101 { 102 is = new FileInputStream( rulesFileName ); 103 } 104 catch ( IOException ioe ) 105 { 106 throw new PluginException( "Unable to process file [" + rulesFileName + "]", ioe ); 107 } 108 109 try 110 { 111 RuleLoader loader = new LoaderFromStream( is ); 112 return loader; 113 } 114 catch ( Exception e ) 115 { 116 throw new PluginException( "Unable to load xmlrules from file [" + rulesFileName + "]", e ); 117 } 118 finally 119 { 120 try 121 { 122 is.close(); 123 } 124 catch ( IOException ioe ) 125 { 126 throw new PluginException( "Unable to close stream for file [" + rulesFileName + "]", ioe ); 127 } 128 } 129 } 130 131 }