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org.apache.turbine.modules.ActionLoader |
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1 | package org.apache.turbine.modules; |
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2 | ||
3 | /* |
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4 | * Copyright 2001-2004 The Apache Software Foundation. |
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5 | * |
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6 | * Licensed under the Apache License, Version 2.0 (the "License") |
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7 | * you may not use this file except in compliance with the License. |
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8 | * You may obtain a copy of the License at |
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9 | * |
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10 | * http://www.apache.org/licenses/LICENSE-2.0 |
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11 | * |
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12 | * Unless required by applicable law or agreed to in writing, software |
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13 | * distributed under the License is distributed on an "AS IS" BASIS, |
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14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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15 | * See the License for the specific language governing permissions and |
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16 | * limitations under the License. |
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17 | */ |
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18 | ||
19 | import java.util.List; |
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20 | ||
21 | import org.apache.commons.logging.Log; |
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22 | import org.apache.commons.logging.LogFactory; |
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23 | ||
24 | import org.apache.turbine.Turbine; |
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25 | import org.apache.turbine.TurbineConstants; |
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26 | import org.apache.turbine.services.assemblerbroker.AssemblerBrokerService; |
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27 | import org.apache.turbine.services.assemblerbroker.TurbineAssemblerBroker; |
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28 | import org.apache.turbine.util.ObjectUtils; |
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29 | import org.apache.turbine.util.RunData; |
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30 | ||
31 | /** |
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32 | * The purpose of this class is to allow one to load and execute |
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33 | * Action modules. |
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34 | * |
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35 | * @author <a href="mailto:mbryson@mont.mindspring.com">Dave Bryson</a> |
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36 | * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a> |
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37 | * @version $Id: ActionLoader.java,v 1.9.2.3 2004/08/16 22:57:50 henning Exp $ |
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38 | */ |
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39 | public class ActionLoader |
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40 | extends GenericLoader |
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41 | { |
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42 | /** Logging */ |
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43 | 0 | private static Log log = LogFactory.getLog(ActionLoader.class); |
44 | ||
45 | /** The single instance of this class. */ |
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46 | 0 | private static ActionLoader instance = new ActionLoader( |
47 | Turbine.getConfiguration().getInt(TurbineConstants.ACTION_CACHE_SIZE_KEY, |
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48 | TurbineConstants.ACTION_CACHE_SIZE_DEFAULT)); |
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49 | ||
50 | /** The Assembler Broker Service */ |
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51 | 0 | private static AssemblerBrokerService ab = TurbineAssemblerBroker.getService(); |
52 | ||
53 | /** |
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54 | * These ctor's are private to force clients to use getInstance() |
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55 | * to access this class. |
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56 | */ |
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57 | private ActionLoader() |
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58 | { |
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59 | 0 | super(); |
60 | 0 | } |
61 | ||
62 | /** |
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63 | * These ctor's are private to force clients to use getInstance() |
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64 | * to access this class. |
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65 | */ |
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66 | private ActionLoader(int i) |
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67 | { |
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68 | 0 | super(i); |
69 | 0 | } |
70 | ||
71 | /** |
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72 | * Adds an instance of an object into the hashtable. |
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73 | * |
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74 | * @param name Name of object. |
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75 | * @param action Action to be associated with name. |
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76 | */ |
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77 | private void addInstance(String name, Action action) |
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78 | { |
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79 | 0 | if (cache()) |
80 | { |
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81 | 0 | this.put(name, (Action) action); |
82 | } |
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83 | 0 | } |
84 | ||
85 | /** |
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86 | * Attempts to load and execute the external action. |
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87 | * |
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88 | * @param data Turbine information. |
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89 | * @param name Name of object that will execute the action. |
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90 | * @exception Exception a generic exception. |
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91 | */ |
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92 | public void exec(RunData data, String name) |
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93 | throws Exception |
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94 | { |
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95 | // Execute action |
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96 | 0 | getInstance(name).perform(data); |
97 | 0 | } |
98 | ||
99 | /** |
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100 | * Pulls out an instance of the object by name. Name is just the |
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101 | * single name of the object. |
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102 | * |
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103 | * @param name Name of object instance. |
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104 | * @return An Action with the specified name, or null. |
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105 | * @exception Exception a generic exception. |
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106 | */ |
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107 | public Action getInstance(String name) |
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108 | throws Exception |
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109 | { |
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110 | 0 | Action action = null; |
111 | ||
112 | // Check if the action is already in the cache |
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113 | 0 | if (cache() && this.containsKey(name)) |
114 | { |
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115 | 0 | action = (Action) this.get(name); |
116 | 0 | log.debug("Found Action " + name + " in the cache!"); |
117 | } |
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118 | else |
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119 | { |
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120 | 0 | log.debug("Loading Action " + name + " from the Assembler Broker"); |
121 | ||
122 | try |
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123 | { |
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124 | // Attempt to load the screen |
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125 | 0 | action = (Action) ab.getAssembler( |
126 | AssemblerBrokerService.ACTION_TYPE, name); |
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127 | } |
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128 | 0 | catch (ClassCastException cce) |
129 | { |
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130 | // This can alternatively let this exception be thrown |
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131 | // So that the ClassCastException is shown in the |
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132 | // browser window. Like this it shows "Screen not Found" |
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133 | 0 | action = null; |
134 | 0 | } |
135 | ||
136 | 0 | if (action == null) |
137 | { |
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138 | // If we did not find a screen we should try and give |
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139 | // the user a reason for that... |
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140 | // FIX ME: The AssemblerFactories should each add it's |
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141 | // own string here... |
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142 | 0 | List packages = Turbine.getConfiguration() |
143 | .getList(TurbineConstants.MODULE_PACKAGES); |
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144 | ||
145 | 0 | ObjectUtils.addOnce(packages, |
146 | GenericLoader.getBasePackage()); |
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147 | ||
148 | 0 | throw new ClassNotFoundException( |
149 | "\n\n\tRequested Action not found: " + name + |
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150 | "\n\tTurbine looked in the following " + |
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151 | "modules.packages path: \n\t" + packages.toString() + "\n"); |
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152 | } |
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153 | 0 | else if (cache()) |
154 | { |
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155 | // The new instance is added to the cache |
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156 | 0 | addInstance(name, action); |
157 | } |
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158 | } |
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159 | 0 | return action; |
160 | } |
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161 | ||
162 | /** |
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163 | * The method through which this class is accessed. |
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164 | * |
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165 | * @return The single instance of this class. |
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166 | */ |
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167 | public static ActionLoader getInstance() |
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168 | { |
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169 | 0 | return instance; |
170 | } |
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171 | } |
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