1 /*
2 * $Id$
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 package org.apache.struts.dispatcher;
22
23 import org.apache.struts.chain.contexts.ActionContext;
24
25 /**
26 * This abstract class is a template for choosing the target method that is
27 * identified by a submission parameter.
28 *
29 * @version $Rev$
30 * @since Struts 1.4
31 */
32 public abstract class AbstractParameterDispatcher extends AbstractDispatcher {
33 private static final long serialVersionUID = -9048942314641198669L;
34
35 /**
36 * The default parameter name if no parameter is set.
37 *
38 * @see #getDefaultParameterName()
39 */
40 protected static final String DEFAULT_PARAMETER_NAME = "method";
41
42 /**
43 * Constructs a new dispatcher with the specified method resolver.
44 *
45 * @param methodResolver the method resolver
46 */
47 public AbstractParameterDispatcher(MethodResolver methodResolver) {
48 super(methodResolver);
49 }
50
51 /**
52 * Retrieves the name of the parameter to fallback upon if the action
53 * configuration did not set the <code>parameter</code> attribute. The
54 * default implementation returns {@link #DEFAULT_PARAMETER_NAME}.
55 *
56 * @return the fallback parameter name; can be <code>null</code>
57 * @see #DEFAULT_PARAMETER_NAME
58 * @see #getParameter(ActionContext)
59 */
60 protected String getDefaultParameterName() {
61 return DEFAULT_PARAMETER_NAME;
62 }
63
64 /**
65 * Retrieves the parameter name whose value will identity the intended
66 * method to dispatch. The value is not necessarily a method name, but a key
67 * that can resolve to one. The default implementation returns the mapping's
68 * <code>parameter</code> attribute; otherwise fallback to the default
69 * parameter name.
70 *
71 * @param context the current action context
72 * @return the mapping's parameter name
73 * @see #getDefaultParameterName()
74 */
75 protected String getParameter(ActionContext context) {
76 String parameter = context.getActionConfig().getParameter();
77 if ((parameter != null) && (parameter.trim().length() > 0)) {
78 return parameter;
79 }
80 return getDefaultParameterName();
81 }
82
83 protected final String resolveMethodName(ActionContext context) {
84 String parameter = getParameter(context);
85 if ("".equals(parameter)) {
86 parameter = null;
87 }
88
89 if (parameter != null) {
90 return resolveParameterValue(context, parameter);
91 }
92
93 return null;
94 }
95
96 /**
97 * Extracts the value that is keyed by the specified parameter.
98 *
99 * @param context the current action context
100 * @param parameter the parameter name
101 * @return the parameter value
102 */
103 protected abstract String resolveParameterValue(ActionContext context, String parameter);
104
105 }