1 package org.apache.turbine.modules;
2
3 /* ====================================================================
4 * The Apache Software License, Version 1.1
5 *
6 * Copyright (c) 2001 The Apache Software Foundation. All rights
7 * reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 *
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 *
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in
18 * the documentation and/or other materials provided with the
19 * distribution.
20 *
21 * 3. The end-user documentation included with the redistribution,
22 * if any, must include the following acknowledgment:
23 * "This product includes software developed by the
24 * Apache Software Foundation (http://www.apache.org/)."
25 * Alternately, this acknowledgment may appear in the software itself,
26 * if and wherever such third-party acknowledgments normally appear.
27 *
28 * 4. The names "Apache" and "Apache Software Foundation" and
29 * "Apache Turbine" must not be used to endorse or promote products
30 * derived from this software without prior written permission. For
31 * written permission, please contact apache@apache.org.
32 *
33 * 5. Products derived from this software may not be called "Apache",
34 * "Apache Turbine", nor may "Apache" appear in their name, without
35 * prior written permission of the Apache Software Foundation.
36 *
37 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
38 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
39 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
40 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
41 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
42 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
43 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
44 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
45 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
46 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
47 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
48 * SUCH DAMAGE.
49 * ====================================================================
50 *
51 * This software consists of voluntary contributions made by many
52 * individuals on behalf of the Apache Software Foundation. For more
53 * information on the Apache Software Foundation, please see
54 * <http://www.apache.org/>.
55 */
56
57 // Java Core Classes
58 import java.util.Vector;
59
60 // Turbine Utility Classes
61 import org.apache.turbine.TurbineConstants;
62 import org.apache.turbine.services.TurbineServices;
63 import org.apache.turbine.services.assemblerbroker.AssemblerBrokerService;
64 import org.apache.turbine.services.resources.TurbineResources;
65 import org.apache.turbine.util.ObjectUtils;
66 import org.apache.turbine.util.RunData;
67
68 /***
69 * The purpose of this class is to allow one to load and execute
70 * Action modules.
71 *
72 * @author <a href="mailto:mbryson@mont.mindspring.com">Dave Bryson</a>
73 * @version $Id: ActionLoader.java,v 1.1.1.1 2001/08/16 05:08:29 jvanzyl Exp $
74 */
75 public class ActionLoader extends GenericLoader
76 {
77 /*** The single instance of this class. */
78 private static ActionLoader instance = new ActionLoader(
79 TurbineResources.getInt(TurbineConstants.ACTION_CACHE_SIZE, 20));
80
81 /***
82 * These ctor's are private to force clients to use getInstance()
83 * to access this class.
84 */
85 private ActionLoader()
86 {
87 super();
88 }
89
90 /***
91 * These ctor's are private to force clients to use getInstance()
92 * to access this class.
93 */
94 private ActionLoader(int i)
95 {
96 super(i);
97 }
98
99 /***
100 * Adds an instance of an object into the hashtable.
101 *
102 * @param name Name of object.
103 * @param action Action to be associated with name.
104 */
105 private void addInstance( String name, Action action )
106 {
107 if ( cache() )
108 this.put( name, (Action) action );
109 }
110
111 /***
112 * Attempts to load and execute the external action.
113 *
114 * @param data Turbine information.
115 * @param name Name of object that will execute the action.
116 * @exception Exception a generic exception.
117 */
118 public void exec( RunData data, String name )
119 throws Exception
120 {
121 // Execute action
122 getInstance(name).perform(data);
123 }
124
125 /***
126 * Pulls out an instance of the object by name. Name is just the
127 * single name of the object.
128 *
129 * @param name Name of object instance.
130 * @return An Action with the specified name, or null.
131 * @exception Exception a generic exception.
132 */
133 public Action getInstance(String name)
134 throws Exception
135 {
136 Action action = null;
137
138 if ( cache() && this.containsKey( name ) )
139 {
140 action = (Action) this.get( name );
141 }
142 else
143 {
144 // We get the broker service
145 AssemblerBrokerService ab =
146 (AssemblerBrokerService)TurbineServices.getInstance()
147 .getService(AssemblerBrokerService.SERVICE_NAME);
148
149 try
150 {
151 // Attempt to load the screen
152 action = (Action) ab.getAssembler(
153 AssemblerBrokerService.ACTION_TYPE,name);
154 }
155 catch (ClassCastException cce)
156 {
157 // This can alternatively let this exception be thrown
158 // So that the ClassCastException is shown in the
159 // browser window. Like this it shows "Screen not Found"
160 action = null;
161 }
162
163 if (action == null)
164 {
165 // If we did not find a screen we should try and give
166 // the user a reason for that...
167 // FIX ME: The AssemblerFactories should each add it's own
168 // string here...
169 Vector packages = TurbineResources.getVector(
170 TurbineConstants.MODULE_PACKAGES);
171 ObjectUtils.addOnce( packages,
172 GenericLoader.getBasePackage() );
173
174 throw new ClassNotFoundException(
175 "\n\n\tRequested Action not found: " + name + "\n" +
176 "\tTurbine looked in the following modules.packages " +
177 "path: \n\t" + packages.toString() + "\n");
178 }
179 else if ( cache() )
180 {
181 // The new instance is added to the cache
182 addInstance( name, action );
183 }
184 }
185 return action;
186 }
187
188 /***
189 * The method through which this class is accessed.
190 *
191 * @return The single instance of this class.
192 */
193 public static ActionLoader getInstance()
194 {
195 return instance;
196 }
197 }
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