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.TurbineServices;
29 import org.apache.turbine.services.assemblerbroker.AssemblerBrokerService;
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;
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 ab = (AssemblerBrokerService)TurbineServices.getInstance().getService(AssemblerBrokerService.SERVICE_NAME);
62 }
63
64 /**
65 * Attempts to load and execute the external action that has been
66 * set.
67 * @param pipelineData the Turbine request
68 * @param name the name of the assembler module
69 * @throws Exception a generic exception.
70 */
71 public abstract void exec(PipelineData pipelineData, String name)
72 throws Exception;
73
74 /**
75 * Returns whether or not this external action is reload itself.
76 * This is in cases where the Next button would be clicked, but
77 * since we are checking for that, we would go into an endless
78 * loop.
79 *
80 * @return True if the action is reload.
81 */
82 public boolean reload()
83 {
84 return this.reload;
85 }
86
87 /**
88 * Sets whether or not this external action is reload itself.
89 * This is in cases where the Next button would be clicked, but
90 * since we are checking for that, we would go into an endless
91 * loop.
92 *
93 * @param reload True if the action must be marked as reload.
94 * @return Itself.
95 */
96 public GenericLoader<T> setReload(boolean reload)
97 {
98 this.reload = reload;
99 return this;
100 }
101
102 /**
103 * Gets the base package where Turbine should find its default
104 * modules.
105 *
106 * @return A String with the base package name.
107 */
108 public static String getBasePackage()
109 {
110 return TURBINE_PACKAGE;
111 }
112
113 /**
114 * Gets the package list where Turbine should find its
115 * modules.
116 *
117 * @return A List with the package names (including the base package).
118 */
119 public static List<String> getPackages()
120 {
121 if (TURBINE_PACKAGES == null)
122 {
123 List<String> turbinePackages = new ArrayList<String>();
124 List<Object> configTurbinePackages =
125 Turbine.getConfiguration()
126 .getList(TurbineConstants.MODULE_PACKAGES);
127 for (Object o : configTurbinePackages)
128 {
129 turbinePackages.add((String)o);
130 }
131
132 TURBINE_PACKAGES = turbinePackages;
133 }
134
135 List<String> packages = TURBINE_PACKAGES;
136
137 if (!packages.contains(TURBINE_PACKAGE))
138 {
139 packages.add(TURBINE_PACKAGE);
140 }
141
142 return packages;
143 }
144
145 /**
146 * Pulls out an instance of the object by name. Name is just the
147 * single name of the object.
148 *
149 * @param type Type of the assembler.
150 * @param name Name of object instance.
151 * @return A Screen with the specified name, or null.
152 * @throws Exception a generic exception.
153 */
154 protected T getAssembler(Class<T> type, String name)
155 throws Exception
156 {
157 T asm = null;
158
159 try
160 {
161 if (ab != null)
162 {
163 // Attempt to load the assembler
164 asm = ab.getAssembler(type, name);
165 }
166 }
167 catch (ClassCastException cce)
168 {
169 // This can alternatively let this exception be thrown
170 // So that the ClassCastException is shown in the
171 // browser window. Like this it shows "Screen not Found"
172 asm = null;
173 }
174
175 if (asm == null)
176 {
177 // If we did not find a screen we should try and give
178 // the user a reason for that...
179 // FIX ME: The AssemblerFactories should each add it's
180 // own string here...
181 List<String> packages = GenericLoader.getPackages();
182
183 throw new ClassNotFoundException(
184 "\n\n\tRequested " + type + " not found: " + name +
185 "\n\tTurbine looked in the following " +
186 "modules.packages path: \n\t" + packages.toString() + "\n");
187 }
188
189 return asm;
190 }
191 }