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.chain.Catalog;
20 import org.apache.commons.chain.Chain;
21 import org.apache.commons.chain.Command;
22 import org.apache.commons.chain.Context;
23 import org.apache.commons.digester.Rule;
24 import org.xml.sax.Attributes;
25
26 /**
27 * 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.
33 *
34 * @author Craig R. McClanahan
35 * @version $Revision$ $Date$
36 */
37 class ConfigRegisterRule extends Rule {
38
39 // ----------------------------------------------------- Instance Variables
40
41 /**
42 * The name of the attribute under which we can retrieve the name
43 * this command should be registered with.
44 */
45 private final String nameAttribute;
46
47 // ----------------------------------------------------------- Constructors
48
49 /**
50 * Construct a new instance of this rule that looks for an attribute
51 * with the specified name.
52 *
53 * @param nameAttribute Name of the attribute containing the name under
54 * which this command should be registered
55 */
56 ConfigRegisterRule(String nameAttribute) {
57 this.nameAttribute = nameAttribute;
58 }
59
60 // --------------------------------------------------------- Public Methods
61
62 /**
63 * Register the top {@link Command} if appropriate.
64 *
65 * @param namespace the namespace URI of the matching element, or an
66 * empty string if the parser is not namespace aware or the
67 * element has no namespace
68 * @param name the local name if the parser is namespace aware, or
69 * just the element name otherwise
70 * @param attributes The attribute list of this element
71 */
72 @Override
73 public void begin(String namespace, String name, Attributes attributes)
74 throws Exception {
75
76 // Is the top object a Command?
77 Object top = digester.peek(0);
78 if (!(top instanceof Command)) {
79 return;
80 }
81
82 /* All commands can consume a generic context. Here we depend on
83 * the configuration being correct because the rule binding is
84 * dynamic. */
85 @SuppressWarnings("unchecked")
86 Command<Context> command = (Command<Context>) top;
87
88 // Is the next object a Catalog or a Chain?
89 Object next = digester.peek(1);
90 if (next == null) {
91 return;
92 }
93
94 // Register the top element appropriately
95 if (next instanceof Catalog) {
96 String nameValue = attributes.getValue(nameAttribute);
97 if (nameValue != null) {
98 /* We are dynamically building a catalog and assigning
99 * generics to the most base types possible. */
100 @SuppressWarnings("unchecked")
101 Catalog<Context> catalog = (Catalog<Context>) next;
102 catalog.addCommand(nameValue, command);
103 }
104 } else if (next instanceof Chain) {
105 /* Like above - the chain is being dynamically generated,
106 * so we can add a generic context signature at compile-time. */
107 @SuppressWarnings("unchecked")
108 Chain<Context> chain = (Chain<Context>) next;
109 chain.addCommand(command);
110 }
111 }
112 }