001 /* $Id: PluginDeclarationRule.java 992060 2010-09-02 19:09:47Z simonetripodi $
002 *
003 * Licensed to the Apache Software Foundation (ASF) under one or more
004 * contributor license agreements. See the NOTICE file distributed with
005 * this work for additional information regarding copyright ownership.
006 * The ASF licenses this file to You under the Apache License, Version 2.0
007 * (the "License"); you may not use this file except in compliance with
008 * the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019 package org.apache.commons.digester.plugins;
020
021 import java.util.Properties;
022
023 import org.apache.commons.digester.Digester;
024 import org.apache.commons.digester.Rule;
025
026 /**
027 * A Digester rule which allows the user to pre-declare a class which is to
028 * be referenced later at a plugin point by a PluginCreateRule.
029 * <p>
030 * Normally, a PluginDeclarationRule is added to a Digester instance with
031 * the pattern "{root}/plugin" or "* /plugin" where {root} is the name of
032 * the root tag in the input document.
033 *
034 * @since 1.6
035 */
036
037 public class PluginDeclarationRule extends Rule {
038
039 //------------------- constructors ---------------------------------------
040
041 /** constructor */
042 public PluginDeclarationRule() {
043 super();
044 }
045
046 //------------------- methods --------------------------------------------
047
048 /**
049 * Invoked upon reading a tag defining a plugin declaration. The tag
050 * must have the following mandatory attributes:
051 * <ul>
052 * <li> id </li>
053 * <li> class </li>
054 * </ul>
055 *
056 *@param namespace The xml namespace in which the xml element which
057 * triggered this rule resides.
058 *@param name The name of the xml element which triggered this rule.
059 *@param attributes The set of attributes on the xml element which
060 * triggered this rule.
061 *@exception java.lang.Exception
062 */
063
064 @Override
065 public void begin(String namespace, String name,
066 org.xml.sax.Attributes attributes)
067 throws java.lang.Exception {
068
069 int nAttrs = attributes.getLength();
070 Properties props = new Properties();
071 for(int i=0; i<nAttrs; ++i) {
072 String key = attributes.getLocalName(i);
073 if ((key == null) || (key.length() == 0)) {
074 key = attributes.getQName(i);
075 }
076 String value = attributes.getValue(i);
077 props.setProperty(key, value);
078 }
079
080 try {
081 declarePlugin(digester, props);
082 } catch(PluginInvalidInputException ex) {
083 throw new PluginInvalidInputException(
084 "Error on element [" + digester.getMatch() +
085 "]: " + ex.getMessage());
086 }
087 }
088
089 public static void declarePlugin(Digester digester, Properties props)
090 throws PluginException {
091
092 String id = props.getProperty("id");
093 String pluginClassName = props.getProperty("class");
094
095 if (id == null) {
096 throw new PluginInvalidInputException(
097 "mandatory attribute id not present on plugin declaration");
098 }
099
100 if (pluginClassName == null) {
101 throw new PluginInvalidInputException(
102 "mandatory attribute class not present on plugin declaration");
103 }
104
105 Declaration newDecl = new Declaration(pluginClassName);
106 newDecl.setId(id);
107 newDecl.setProperties(props);
108
109 PluginRules rc = (PluginRules) digester.getRules();
110 PluginManager pm = rc.getPluginManager();
111
112 newDecl.init(digester, pm);
113 pm.addDeclaration(newDecl);
114
115 // Note that it is perfectly safe to redeclare a plugin, because
116 // the declaration doesn't add any rules to digester; all it does
117 // is create a RuleLoader instance whch is *capable* of adding the
118 // rules to the digester.
119 }
120 }
121