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org.apache.turbine.modules.PageLoader |
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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 Page |
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33 | * 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: PageLoader.java,v 1.8.2.3 2004/08/16 22:57:50 henning Exp $ |
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38 | */ |
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39 | public class PageLoader |
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40 | extends GenericLoader |
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41 | implements Loader |
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42 | { |
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43 | /** Logging */ |
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44 | 34 | private static Log log = LogFactory.getLog(PageLoader.class); |
45 | ||
46 | /** The single instance of this class. */ |
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47 | 17 | private static PageLoader instance = |
48 | new PageLoader(Turbine.getConfiguration() |
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49 | .getInt(TurbineConstants.PAGE_CACHE_SIZE_KEY, |
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50 | TurbineConstants.PAGE_CACHE_SIZE_DEFAULT)); |
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51 | ||
52 | /** The Assembler Broker Service */ |
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53 | 17 | private static AssemblerBrokerService ab = TurbineAssemblerBroker.getService(); |
54 | ||
55 | /** |
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56 | * These ctor's are private to force clients to use getInstance() |
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57 | * to access this class. |
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58 | */ |
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59 | private PageLoader() |
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60 | { |
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61 | 0 | super(); |
62 | 0 | } |
63 | ||
64 | /** |
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65 | * These ctor's are private to force clients to use getInstance() |
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66 | * to access this class. |
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67 | */ |
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68 | private PageLoader(int i) |
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69 | { |
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70 | 17 | super(i); |
71 | 17 | } |
72 | ||
73 | /** |
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74 | * Adds an instance of an object into the hashtable. |
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75 | * |
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76 | * @param name Name of object. |
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77 | * @param page Page to be associated with name. |
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78 | */ |
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79 | private void addInstance(String name, Page page) |
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80 | { |
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81 | 0 | if (cache()) |
82 | { |
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83 | 0 | this.put(name, (Page) page); |
84 | } |
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85 | 0 | } |
86 | ||
87 | /** |
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88 | * Attempts to load and execute the external page. |
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89 | * |
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90 | * @param data Turbine information. |
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91 | * @param name Name of object that will execute the page. |
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92 | * @exception Exception a generic exception. |
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93 | */ |
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94 | public void exec(RunData data, String name) |
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95 | throws Exception |
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96 | { |
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97 | // Execute page |
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98 | 0 | getInstance(name).build(data); |
99 | 0 | } |
100 | ||
101 | /** |
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102 | * Pulls out an instance of the object by name. Name is just the |
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103 | * single name of the object. This is equal to getInstance but |
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104 | * returns an Assembler object and is needed to fulfil the Loader |
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105 | * interface. |
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106 | * |
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107 | * @param name Name of object instance. |
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108 | * @return A Screen with the specified name, or null. |
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109 | * @exception Exception a generic exception. |
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110 | */ |
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111 | public Assembler getAssembler(String name) |
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112 | throws Exception |
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113 | { |
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114 | 0 | return getInstance(name); |
115 | } |
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116 | ||
117 | /** |
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118 | * Pulls out an instance of the page by name. Name is just the |
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119 | * single name of the page. |
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120 | * |
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121 | * @param name Name of object instance. |
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122 | * @return A Page with the specified name, or null. |
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123 | * @exception Exception a generic exception. |
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124 | */ |
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125 | public Page getInstance(String name) |
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126 | throws Exception |
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127 | { |
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128 | 0 | Page page = null; |
129 | ||
130 | // Check if the screen is already in the cache |
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131 | 0 | if (cache() && this.containsKey(name)) |
132 | { |
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133 | 0 | page = (Page) this.get(name); |
134 | 0 | log.debug("Found Page " + name + " in the cache!"); |
135 | } |
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136 | else |
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137 | { |
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138 | 0 | log.debug("Loading Page " + name + " from the Assembler Broker"); |
139 | ||
140 | try |
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141 | { |
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142 | 0 | if (ab != null) |
143 | { |
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144 | // Attempt to load the screen |
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145 | 0 | page = (Page) ab.getAssembler( |
146 | AssemblerBrokerService.PAGE_TYPE, name); |
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147 | } |
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148 | } |
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149 | 0 | catch (ClassCastException cce) |
150 | { |
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151 | // This can alternatively let this exception be thrown |
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152 | // So that the ClassCastException is shown in the |
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153 | // browser window. Like this it shows "Screen not Found" |
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154 | 0 | page = null; |
155 | 0 | } |
156 | ||
157 | 0 | if (page == null) |
158 | { |
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159 | // If we did not find a screen we should try and give |
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160 | // the user a reason for that... |
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161 | // FIX ME: The AssemblerFactories should each add it's |
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162 | // own string here... |
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163 | 0 | List packages = Turbine.getConfiguration() |
164 | .getList(TurbineConstants.MODULE_PACKAGES); |
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165 | ||
166 | 0 | ObjectUtils.addOnce(packages, |
167 | GenericLoader.getBasePackage()); |
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168 | ||
169 | 0 | throw new ClassNotFoundException( |
170 | "\n\n\tRequested Page not found: " + name + |
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171 | "\n\tTurbine looked in the following " + |
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172 | "modules.packages path: \n\t" + packages.toString() + "\n"); |
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173 | } |
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174 | 0 | else if (cache()) |
175 | { |
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176 | // The new instance is added to the cache |
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177 | 0 | addInstance(name, page); |
178 | } |
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179 | } |
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180 | 0 | return page; |
181 | } |
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182 | ||
183 | /** |
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184 | * The method through which this class is accessed. |
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185 | * |
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186 | * @return The single instance of this class. |
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187 | */ |
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188 | public static PageLoader getInstance() |
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189 | { |
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190 | 18 | return instance; |
191 | } |
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192 | } |
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