1 | // Copyright 2012 Georg-August-Universität Göttingen, Germany
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2 | //
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3 | // Licensed under the Apache License, Version 2.0 (the "License");
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4 | // you may not use this file except in compliance with the License.
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5 | // You may obtain a copy of the License at
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6 | //
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7 | // http://www.apache.org/licenses/LICENSE-2.0
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8 | //
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9 | // Unless required by applicable law or agreed to in writing, software
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10 | // distributed under the License is distributed on an "AS IS" BASIS,
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11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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12 | // See the License for the specific language governing permissions and
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13 | // limitations under the License.
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14 |
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15 | package de.ugoe.cs.autoquest.jfcmonitor;
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16 |
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17 | import java.io.FileInputStream;
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18 | import java.io.FileNotFoundException;
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19 | import java.io.IOException;
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20 | import java.lang.reflect.InvocationTargetException;
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21 | import java.lang.reflect.Method;
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22 | import java.net.MalformedURLException;
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23 | import java.net.URL;
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24 | import java.net.URLClassLoader;
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25 | import java.util.Arrays;
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26 | import java.util.jar.JarInputStream;
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27 | import java.util.jar.Manifest;
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28 |
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29 | /**
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30 | * <p>
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31 | * Class that launches an executable Jar-file in the same thread and VM where the JarLauncher
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32 | * instance is created. The requirements on the Jar file are:
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33 | * <li>Must contain a MANIFEST.</li>
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34 | * <li>The MANIFEST must define the main-class of the application ("Main-Class" entry).</li>
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35 | * <li>The MANIFEST must define the classpath of the application ("Class-Path" entry).</li>
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36 | * </p>
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37 | *
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38 | * @author Steffen Herbold
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39 | * @version 1.0
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40 | */
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41 | public class JarLauncher {
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42 |
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43 | /**
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44 | * <p>
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45 | * Name of the Jar file to be executed.
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46 | * </p>
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47 | */
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48 | private String jarfile;
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49 |
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50 | /**
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51 | * <p>
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52 | * Arguments for launching the Jar file.
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53 | * </p>
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54 | */
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55 | private String[] args;
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56 |
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57 | /**
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58 | * <p>
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59 | * Helper variable with the path to the working directory.
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60 | * </p>
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61 | */
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62 | final String workingDir = System.getProperty("user.dir") + "/";
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63 |
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64 | /**
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65 | * <p>
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66 | * Internal variable used to store the classpath extracted from the Jar file's MANIFEST.
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67 | * </p>
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68 | */
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69 | private String[] classPath = new String[] { };
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70 |
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71 | /**
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72 | * <p>
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73 | * Internal variable used to store the name (including package information) of the Jar file's
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74 | * main function extracted from the Jar file's MANIFEST.
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75 | * </p>
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76 | */
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77 | private String mainClassName = "";
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78 |
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79 | /**
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80 | * <p>
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81 | * Inner class that defines an exception that is thrown if launching the application in the Jar
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82 | * file fails.
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83 | * </p>
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84 | *
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85 | * @author Steffen Herbold
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86 | * @version 1.0
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87 | */
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88 | private static class JarLaunchException extends Exception {
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89 |
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90 | /**
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91 | * <p>
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92 | * Id for object serialization.
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93 | * </p>
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94 | */
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95 | private static final long serialVersionUID = 1L;
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96 |
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97 | /**
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98 | * <p>
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99 | * Constructor. Creates a new JarLaunchException.
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100 | * </p>
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101 | *
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102 | * @param string
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103 | * error message of the exception
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104 | */
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105 | public JarLaunchException(String string) {
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106 | super(string);
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107 | }
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108 |
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109 | /**
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110 | * <p>
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111 | * Constructor. Creates a new JarLaunchException as a copy of an existing exception.
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112 | * </p>
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113 | *
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114 | * @param e
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115 | * exception that is copied
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116 | */
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117 | public JarLaunchException(Exception e) {
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118 | super(e);
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119 | }
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120 |
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121 | }
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122 |
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123 | /**
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124 | * <p>
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125 | * Constructor. Creates a new JarLauncher.
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126 | * </p>
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127 | *
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128 | * @param jarfile
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129 | * file to be launched; must not be complete path but in relation to the current
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130 | * working directory
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131 | * @param args
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132 | * arguments with which the main function of the Jar file is called
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133 | */
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134 | public JarLauncher(String jarfile, String[] args) {
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135 | this.jarfile = jarfile;
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136 | this.args = Arrays.copyOf(args, args.length);
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137 | }
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138 |
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139 | /**
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140 | * <p>
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141 | * Executes the main function of the Jar file associated with this launcher.
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142 | * </p>
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143 | */
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144 | public void exec() {
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145 | try {
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146 | getInfoFromJar();
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147 | initClassLoader();
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148 | runMain();
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149 | }
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150 | catch (JarLaunchException e) {
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151 | System.err.println("Failure to launch application.");
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152 | System.err.println(e.getMessage());
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153 | }
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154 | }
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155 |
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156 | /**
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157 | * <p>
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158 | * Retrieves the classpath and main function from the Jar file's MANIFEST.
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159 | * </p>
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160 | *
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161 | * @throws JarLaunchException
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162 | * thrown if reading of Jar file or MANIFEST fails
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163 | */
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164 | private void getInfoFromJar() throws JarLaunchException {
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165 | JarInputStream jarInputStream;
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166 | try {
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167 | jarInputStream = new JarInputStream(new FileInputStream(workingDir + jarfile));
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168 | }
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169 | catch (FileNotFoundException e) {
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170 | throw new JarLaunchException(e);
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171 | }
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172 | catch (IOException e) {
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173 | throw new JarLaunchException(e);
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174 | }
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175 | Manifest manifest = jarInputStream.getManifest();
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176 | mainClassName = manifest.getMainAttributes().getValue("Main-Class");
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177 | String jarClassPath = manifest.getMainAttributes().getValue("Class-Path");
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178 | String[] jarClassPathElements = jarClassPath.split(" ");
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179 | classPath = new String[jarClassPathElements.length];
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180 | for (int i = 0; i < jarClassPathElements.length; i++) {
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181 | classPath[i] = "file:" + workingDir + jarClassPathElements[i];
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182 | }
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183 | try {
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184 | jarInputStream.close();
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185 | }
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186 | catch (IOException e) {
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187 | e.printStackTrace();
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188 | }
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189 | }
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190 |
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191 | /**
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192 | * <p>
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193 | * Modifies the {@link ClassLoader} of the current VM such that it includes the class path
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194 | * defined in the Jar file's MANIFEST.
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195 | * </p>
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196 | *
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197 | * @throws JarLaunchException
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198 | * thrown if modification of {@link ClassLoader} fails.
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199 | */
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200 | private void initClassLoader() throws JarLaunchException {
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201 | URLClassLoader classLoader = (URLClassLoader) ClassLoader.getSystemClassLoader();
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202 | Method method;
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203 | try {
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204 | method = URLClassLoader.class.getDeclaredMethod("addURL", new Class[]
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205 | { URL.class });
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206 | }
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207 | catch (SecurityException e) {
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208 | throw new JarLaunchException(
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209 | "addURL method of URLClassLoader not accessible via reflection.");
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210 | }
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211 | catch (NoSuchMethodException e) {
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212 | throw new JarLaunchException(
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213 | "URLClassLoader does not have addURL method. Should be impossible!!");
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214 | }
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215 | method.setAccessible(true);
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216 |
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217 | try {
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218 | method.invoke(classLoader, new Object[]
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219 | { new URL("file:" + workingDir + jarfile) });
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220 | for (String element : classPath) {
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221 | method.invoke(classLoader, new Object[]
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222 | { new URL(element) });
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223 | }
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224 | }
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225 | catch (IllegalArgumentException e) {
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226 | throw new JarLaunchException(
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227 | "Illegal arguments for addURL method. Should be impossible!!");
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228 | }
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229 | catch (MalformedURLException e) {
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230 | throw new JarLaunchException(e);
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231 | }
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232 | catch (IllegalAccessException e) {
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233 | throw new JarLaunchException(
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234 | "addURL method of URLClassLoader not accessible via reflection.");
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235 | }
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236 | catch (InvocationTargetException e) {
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237 | e.printStackTrace();
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238 | }
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239 | }
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240 |
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241 | /**
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242 | * <p>
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243 | * Executes the main function.
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244 | * </p>
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245 | *
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246 | * @throws JarLaunchException
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247 | * thrown if execution of main function fails or the main function itself throws an
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248 | * exception
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249 | */
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250 | private void runMain() throws JarLaunchException {
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251 | Class<?> mainClass;
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252 | try {
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253 | mainClass = Class.forName(mainClassName);
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254 | }
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255 | catch (ClassNotFoundException e) {
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256 | throw new JarLaunchException("Main class not found: " + mainClassName);
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257 | }
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258 | Method mainMethod;
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259 | try {
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260 | mainMethod = mainClass.getMethod("main", new Class[]
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261 | { String[].class });
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262 | }
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263 | catch (SecurityException e) {
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264 | throw new JarLaunchException("Main method not accessible.");
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265 | }
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266 | catch (NoSuchMethodException e) {
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267 | throw new JarLaunchException("Main method not found.");
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268 | }
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269 | try {
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270 | mainMethod.invoke(null, new Object[]
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271 | { args });
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272 | }
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273 | catch (IllegalArgumentException e) {
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274 | throw new JarLaunchException(
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275 | "Illegal arguments for main method. Should be impossible!!");
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276 | }
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277 | catch (IllegalAccessException e) {
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278 | throw new JarLaunchException("Main method not accessible.");
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279 | }
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280 | catch (InvocationTargetException e) {
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281 | throw new JarLaunchException(e);
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282 | }
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283 | }
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284 | }
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