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Java > Open Source Codes > org > apache > commons > chain > config > ConfigRegisterRule


1 /*
2  * Copyright 1999-2004 The Apache Software Foundation
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package org.apache.commons.chain.config;
17
18
19 import org.apache.commons.chain.Catalog;
20 import org.apache.commons.chain.Chain;
21 import org.apache.commons.chain.Command;
22 import org.apache.commons.digester.Rule;
23 import org.xml.sax.Attributes JavaDoc;
24
25
26 /**
27  * <p>Digester rule that will cause the top-most element on the Digester
28  * stack (if it is a {@link Command} to be registered with the next-to-top
29  * element on the Digester stack (if it is a {@link Catalog} or {@link Chain}).
30  * To be registered with a {@link Catalog}, the top-most element must contain
31  * a value for the specified attribute that contains the name under which
32  * it should be registered.</p>
33  *
34  * @author Craig R. McClanahan
35  * @version $Revision: 1.5 $ $Date: 2004/11/30 05:52:23 $
36  */
37 class ConfigRegisterRule extends Rule {
38
39
40     // ----------------------------------------------------------- Constructors
41
42
43     /**
44      * <p>Construct a new instance of this rule that looks for an attribute
45      * with the specified name.</p>
46      *
47      * @param nameAttribute Name of the attribute containing the name under
48      * which this command should be registered
49      */
50     public ConfigRegisterRule(String JavaDoc nameAttribute) {
51         super();
52         this.nameAttribute = nameAttribute;
53     }
54
55
56     // ----------------------------------------------------- Instance Variables
57
58
59     /**
60      * <p>The name of the attribute under which we can retrieve the name
61      * this command should be registered with.</p>
62      */
63     private String JavaDoc nameAttribute = null;
64
65
66     // --------------------------------------------------------- Public Methods
67
68
69     /**
70      * <p>Register the top {@link Command} if appropriate.</p>
71      *
72      * @param namespace the namespace URI of the matching element, or an
73      * empty string if the parser is not namespace aware or the element has
74      * no namespace
75      * @param name the local name if the parser is namespace aware, or just
76      * the element name otherwise
77      * @param attributes The attribute list of this element
78      */
79     public void begin(String JavaDoc namespace, String JavaDoc name, Attributes JavaDoc attributes)
80         throws Exception JavaDoc {
81
82         // Is the top object a Command?
83 Object JavaDoc top = digester.peek(0);
84         if ((top == null)
85             || !(top instanceof Command)) {
86             return;
87         }
88         Command command = (Command) top;
89
90         // Is the next object a Catalog or a Chain?
91 Object JavaDoc next = digester.peek(1);
92         if (next == null) {
93             return;
94         }
95
96         // Register the top element appropriately
97 if (next instanceof Catalog) {
98             Catalog catalog = (Catalog) next;
99             String JavaDoc nameValue = attributes.getValue(nameAttribute);
100             if (nameValue != null) {
101                 ((Catalog) next).addCommand(nameValue, command);
102             }
103         } else if (next instanceof Chain) {
104             ((Chain) next).addCommand(command);
105         }
106
107     }
108
109
110 }
111
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