1 | package de.ugoe.cs.quest.plugin; |
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2 | |
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3 | import java.io.File; |
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4 | import java.io.FileInputStream; |
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5 | import java.io.FileNotFoundException; |
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6 | import java.io.FilenameFilter; |
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7 | import java.io.IOException; |
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8 | import java.lang.reflect.InvocationTargetException; |
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9 | import java.lang.reflect.Method; |
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10 | import java.net.MalformedURLException; |
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11 | import java.net.URL; |
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12 | import java.net.URLClassLoader; |
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13 | import java.security.InvalidParameterException; |
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14 | import java.util.Collection; |
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15 | import java.util.Collections; |
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16 | import java.util.LinkedList; |
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17 | import java.util.jar.JarInputStream; |
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18 | import java.util.jar.Manifest; |
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19 | |
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20 | /** |
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21 | * <p> |
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22 | * This class provides the functionality to load QUEST plug-ins from a |
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23 | * pre-defined folder. |
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24 | * </p> |
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25 | * |
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26 | * @author Steffen Herbold |
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27 | * @version 1.0 |
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28 | */ |
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29 | public class PluginLoader { |
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30 | |
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31 | /** |
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32 | * <p> |
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33 | * Handle of the plug-in directory. |
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34 | * </p> |
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35 | */ |
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36 | private final File pluginDir; |
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37 | |
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38 | /** |
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39 | * <p> |
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40 | * Collection of the loaded plug-ins. |
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41 | * </p> |
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42 | */ |
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43 | private final Collection<QuestPlugin> plugins; |
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44 | |
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45 | /** |
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46 | * <p> |
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47 | * Constructor. Creates a new PluginLoader that can load plug-ins the |
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48 | * defined directory. |
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49 | * </p> |
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50 | * |
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51 | * @param pluginDir |
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52 | * handle of the directory; in case the handle is |
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53 | * <code>null</code> or does not describe a directory, an |
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54 | * {@link InvalidParameterException} is thrown |
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55 | */ |
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56 | public PluginLoader(File pluginDir) { |
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57 | if (pluginDir == null) { |
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58 | throw new InvalidParameterException( |
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59 | "Parameter pluginDir must not be null!"); |
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60 | } |
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61 | if (!pluginDir.isDirectory()) { |
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62 | throw new InvalidParameterException("File " + pluginDir.getPath() |
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63 | + " is not a directory"); |
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64 | } |
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65 | this.pluginDir = pluginDir; |
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66 | plugins = new LinkedList<QuestPlugin>(); |
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67 | } |
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68 | |
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69 | /** |
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70 | * <p> |
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71 | * Loads plug-ins from {@link #pluginDir}. |
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72 | * </p> |
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73 | * |
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74 | * @throws PluginLoaderException |
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75 | * thrown if there is a problem loading a plug-in or updating |
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76 | * the classpath |
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77 | */ |
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78 | public void load() throws PluginLoaderException { |
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79 | File[] jarFiles = pluginDir.listFiles(new FilenameFilter() { |
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80 | @Override |
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81 | public boolean accept(File dir, String name) { |
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82 | return checkNameConformity(name); |
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83 | } |
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84 | }); |
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85 | |
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86 | for (File jarFile : jarFiles) { |
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87 | updateClassLoader(jarFile); |
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88 | |
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89 | String pluginName = jarFile.getName().split("-")[2]; |
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90 | String pluginClassName = "de.ugoe.cs.quest.plugin." + pluginName |
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91 | + "." + pluginName.toUpperCase() + "Plugin"; |
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92 | |
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93 | Class<?> pluginClass = null; |
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94 | try { |
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95 | pluginClass = Class.forName(pluginClassName); |
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96 | } catch (ClassNotFoundException e) { |
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97 | throw new PluginLoaderException("No class '" + pluginClassName |
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98 | + "' found in " + pluginDir + "/" + jarFile.getName()); |
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99 | } |
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100 | try { |
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101 | QuestPlugin pluginObject = (QuestPlugin) pluginClass |
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102 | .newInstance(); |
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103 | plugins.add(pluginObject); |
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104 | } catch (InstantiationException e) { |
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105 | throw new PluginLoaderException("Could not instantiate " |
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106 | + pluginClassName); |
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107 | } catch (IllegalAccessException e) { |
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108 | throw new PluginLoaderException("Could not access " |
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109 | + pluginClassName); |
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110 | } catch (ClassCastException e) { |
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111 | throw new PluginLoaderException("Class " + pluginClassName |
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112 | + " not instance of QuestPlugin"); |
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113 | } |
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114 | } |
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115 | } |
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116 | |
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117 | /** |
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118 | * <p> |
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119 | * Retrieves the classpath from a Jar file's MANIFEST. |
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120 | * </p> |
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121 | * |
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122 | * @throws IOException |
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123 | * @throws FileNotFoundException |
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124 | */ |
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125 | protected String[] getClassPathFromJar(File jarFile) { |
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126 | String[] classPath; |
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127 | |
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128 | JarInputStream jarInputStream = null; |
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129 | try { |
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130 | jarInputStream = new JarInputStream(new FileInputStream(jarFile)); |
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131 | } catch (FileNotFoundException e) { |
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132 | throw new AssertionError( |
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133 | "FileNotFoundException should be impossible!"); |
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134 | } catch (IOException e) { |
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135 | throw new PluginLoaderException(e); |
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136 | } |
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137 | |
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138 | Manifest manifest = jarInputStream.getManifest(); |
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139 | |
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140 | String jarClassPath = manifest.getMainAttributes().getValue( |
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141 | "Class-Path"); |
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142 | |
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143 | if (jarClassPath != null) { |
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144 | String[] jarClassPathElements = jarClassPath.split(" "); |
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145 | classPath = new String[jarClassPathElements.length]; |
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146 | for (int i = 0; i < jarClassPathElements.length; i++) { |
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147 | classPath[i] = "file:" |
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148 | + jarFile.getParentFile().getAbsolutePath() + "/" |
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149 | + jarClassPathElements[i]; |
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150 | } |
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151 | try { |
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152 | jarInputStream.close(); |
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153 | } catch (IOException e) { |
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154 | throw new PluginLoaderException(e); |
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155 | } |
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156 | } else { |
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157 | classPath = new String[] {}; |
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158 | } |
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159 | return classPath; |
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160 | } |
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161 | |
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162 | /** |
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163 | * <p> |
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164 | * Updates the classpath of the {@link ClassLoader} to include the plug-in |
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165 | * jar as well as further libraries required by the plug-in jar as defined |
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166 | * in the <code>Class-Path</code> section of its manifest. |
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167 | * </p> |
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168 | * |
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169 | * @param jarFile |
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170 | * handle of the plug-in jar file |
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171 | * @throws PluginLoaderException |
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172 | * thrown if there is a problem updating the class loader or |
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173 | * loading the plug-in jar |
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174 | */ |
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175 | private void updateClassLoader(File jarFile) throws PluginLoaderException { |
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176 | String[] classPath = getClassPathFromJar(jarFile); |
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177 | URLClassLoader classLoader = (URLClassLoader) ClassLoader |
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178 | .getSystemClassLoader(); |
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179 | Method method; |
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180 | |
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181 | try { |
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182 | method = URLClassLoader.class.getDeclaredMethod("addURL", |
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183 | new Class[] { URL.class }); |
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184 | } catch (SecurityException e) { |
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185 | throw new PluginLoaderException( |
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186 | "addURL method of URLClassLoader not accessible via reflection."); |
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187 | } catch (NoSuchMethodException e) { |
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188 | throw new AssertionError( |
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189 | "URLClassLoader does not have addURL method. Should be impossible!!"); |
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190 | } |
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191 | method.setAccessible(true); |
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192 | |
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193 | try { |
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194 | method.invoke( |
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195 | classLoader, |
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196 | new Object[] { new URL("file:" + jarFile.getAbsoluteFile()) }); |
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197 | for (String element : classPath) { |
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198 | method.invoke(classLoader, new Object[] { new URL(element) }); |
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199 | } |
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200 | } catch (IllegalArgumentException e) { |
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201 | throw new AssertionError( |
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202 | "Illegal arguments for addURL method. Should be impossible!!"); |
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203 | } catch (MalformedURLException e) { |
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204 | throw new PluginLoaderException(e); |
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205 | } catch (IllegalAccessException e) { |
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206 | throw new PluginLoaderException( |
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207 | "addURL method of URLClassLoader not accessible via reflection."); |
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208 | } catch (InvocationTargetException e) { |
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209 | throw new PluginLoaderException(e); |
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210 | } |
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211 | } |
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212 | |
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213 | /** |
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214 | * <p> |
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215 | * Checks if the name of a file indicates that it defines a QUEST plug-in. |
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216 | * The structure of valid plug-in filenames is |
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217 | * <code>quest-plugin-%PLUGIN_NAME%-version.jar</code>, where |
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218 | * <code>%PLUGIN_NAME%</code> is replaced by the name of the plug-in. Note |
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219 | * that plug-in names must not contain any dashes. |
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220 | * </p> |
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221 | * |
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222 | * @param filename |
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223 | * filename that is checked |
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224 | * @return true if filename matches pattern of QUEST plug-in; false |
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225 | * otherwise |
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226 | */ |
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227 | protected boolean checkNameConformity(String filename) { |
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228 | if (filename == null) { |
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229 | return false; |
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230 | } |
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231 | return filename.startsWith("quest-plugin-") |
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232 | && filename.endsWith(".jar") && filename.split("-").length == 4; |
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233 | } |
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234 | |
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235 | public Collection<QuestPlugin> getPlugins() { |
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236 | return Collections.unmodifiableCollection(plugins); |
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237 | } |
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238 | } |
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