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 package org.apache.commons.chain.config;
18
19 import org.apache.commons.digester.Rule;
20 import org.xml.sax.Attributes;
21
22 /**
23 * Digester rule that will dynamically register a new set of rules
24 * for a specified element name and default implementation class. This
25 * allows "alias" elements to be created for {@link org.apache.commons.chain.Chain}
26 * and {@link org.apache.commons.chain.Command}
27 * implementation classes that are commonly used. Besides factoring out
28 * the class names to make changes easier, this also makes configuration
29 * files <strong>much</strong> easier to read and write.
30 *
31 * @version $Revision$ $Date$
32 */
33 class ConfigDefineRule extends Rule {
34
35 // ----------------------------------------------------- Instance Variables
36
37 /**
38 * The name of the attribute under which we can retrieve the
39 * fully qualified class name of the implementation class for this
40 * new element.
41 */
42 private final String classAttribute;
43
44 /**
45 * The name of the attribute under which we can retrieve the name
46 * this element for which rules should be created.
47 */
48 private final String nameAttribute;
49
50 // ----------------------------------------------------------- Constructors
51
52 /**
53 * Construct a new instance of this rule that will in turn
54 * dynamically register appropriate rules for a new alias element.
55 *
56 * @param nameAttribute Name of the attribute containing the name
57 * of the new element for which rules should generated
58 * @param classAttribute Name of the attribute containing the
59 * implementation class for the new chain or command
60 */
61 ConfigDefineRule(String nameAttribute, String classAttribute) {
62 this.nameAttribute = nameAttribute;
63 this.classAttribute = classAttribute;
64 }
65
66 // --------------------------------------------------------- Public Methods
67
68 /**
69 * Register new rules for the specified name and class.
70 *
71 * @param namespace the namespace URI of the matching element, or an
72 * empty string if the parser is not namespace aware or the
73 * element has no namespace
74 * @param name the local name if the parser is namespace aware, or
75 * just the element name otherwise
76 * @param attributes The attribute list of this element
77 */
78 @Override
79 public void begin(String namespace, String name, Attributes attributes)
80 throws Exception {
81
82 // Extract the actual name and implementation class to use
83 String nameValue = attributes.getValue(nameAttribute);
84 String classValue = attributes.getValue(classAttribute);
85
86 // Add rules for this new element
87 digester.addObjectCreate("*/" + nameValue, classValue);
88 digester.addSetProperties("*/" + nameValue);
89 digester.addRule("*/" + nameValue,
90 new ConfigRegisterRule(nameAttribute));
91 }
92 }