1 package org.apache.turbine.modules;
2
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
22 import java.util.ArrayList;
23 import java.util.List;
24
25 import org.apache.turbine.Turbine;
26 import org.apache.turbine.TurbineConstants;
27 import org.apache.turbine.pipeline.PipelineData;
28 import org.apache.turbine.services.assemblerbroker.AssemblerBrokerService;
29 import org.apache.turbine.services.assemblerbroker.TurbineAssemblerBroker;
30
31 /**
32 * This is the base class for the loaders. It contains code that is
33 * used across all of the loaders. It also specifies the interface
34 * that is required to be called a Loader.
35 *
36 * @author <a href="mailto:mbryson@mont.mindspring.com">Dave Bryson</a>
37 * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
38 * @author <a href="mailto:peter@courcoux.biz">Peter Courcoux</a>
39 * @param <T> the specialized assembler type
40 */
41 public abstract class GenericLoader<T extends Assembler>
42 {
43 /** The Assembler Broker Service */
44 protected AssemblerBrokerService ab = TurbineAssemblerBroker.getService();
45
46 /** @serial This can be serialized */
47 private boolean reload = false;
48
49 /** Base packages path for Turbine */
50 private static final String TURBINE_PACKAGE = "org.apache.turbine.modules";
51
52 /** Packages paths for Turbine */
53 private static List<String> TURBINE_PACKAGES = null;
54
55 /**
56 * Basic constructor for creating a loader.
57 */
58 public GenericLoader()
59 {
60 super();
61 }
62
63 /**
64 * Attempts to load and execute the external action that has been
65 * set.
66 * @param pipelineData the Turbine request
67 * @param name the name of the assembler module
68 * @exception Exception a generic exception.
69 */
70 public abstract void exec(PipelineData pipelineData, String name)
71 throws Exception;
72
73 /**
74 * Returns whether or not this external action is reload itself.
75 * This is in cases where the Next button would be clicked, but
76 * since we are checking for that, we would go into an endless
77 * loop.
78 *
79 * @return True if the action is reload.
80 */
81 public boolean reload()
82 {
83 return this.reload;
84 }
85
86 /**
87 * Sets whether or not this external action is reload itself.
88 * This is in cases where the Next button would be clicked, but
89 * since we are checking for that, we would go into an endless
90 * loop.
91 *
92 * @param reload True if the action must be marked as reload.
93 * @return Itself.
94 */
95 public GenericLoader<T> setReload(boolean reload)
96 {
97 this.reload = reload;
98 return this;
99 }
100
101 /**
102 * Gets the base package where Turbine should find its default
103 * modules.
104 *
105 * @return A String with the base package name.
106 */
107 public static String getBasePackage()
108 {
109 return TURBINE_PACKAGE;
110 }
111
112 /**
113 * Gets the package list where Turbine should find its
114 * modules.
115 *
116 * @return A List with the package names (including the base package).
117 */
118 public static List<String> getPackages()
119 {
120 if (TURBINE_PACKAGES == null)
121 {
122 List<String> turbinePackages = new ArrayList<String>();
123 List<Object> configTurbinePackages =
124 Turbine.getConfiguration()
125 .getList(TurbineConstants.MODULE_PACKAGES);
126 for (Object o : configTurbinePackages)
127 {
128 turbinePackages.add((String)o);
129 }
130
131 TURBINE_PACKAGES = turbinePackages;
132 }
133
134 List<String> packages = TURBINE_PACKAGES;
135
136 if (!packages.contains(TURBINE_PACKAGE))
137 {
138 packages.add(TURBINE_PACKAGE);
139 }
140
141 return packages;
142 }
143
144 /**
145 * Pulls out an instance of the object by name. Name is just the
146 * single name of the object.
147 *
148 * @param type Type of the assembler.
149 * @param name Name of object instance.
150 * @return A Screen with the specified name, or null.
151 * @exception Exception a generic exception.
152 */
153 protected T getAssembler(Class<T> type, String name)
154 throws Exception
155 {
156 T asm = null;
157
158 try
159 {
160 if (ab != null)
161 {
162 // Attempt to load the assembler
163 asm = ab.getAssembler(type, name);
164 }
165 }
166 catch (ClassCastException cce)
167 {
168 // This can alternatively let this exception be thrown
169 // So that the ClassCastException is shown in the
170 // browser window. Like this it shows "Screen not Found"
171 asm = null;
172 }
173
174 if (asm == null)
175 {
176 // If we did not find a screen we should try and give
177 // the user a reason for that...
178 // FIX ME: The AssemblerFactories should each add it's
179 // own string here...
180 List<String> packages = GenericLoader.getPackages();
181
182 throw new ClassNotFoundException(
183 "\n\n\tRequested " + type + " not found: " + name +
184 "\n\tTurbine looked in the following " +
185 "modules.packages path: \n\t" + packages.toString() + "\n");
186 }
187
188 return asm;
189 }
190 }