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1
16 import java.io.File  ;
17
18 import java.net.MalformedURLException ;
19 import java.net.URL ;
20 import java.net.URLClassLoader ;
21
22 import java.lang.reflect.InvocationTargetException ;
23 import java.lang.reflect.Method ;
24
25 import java.util.StringTokenizer ;
26
27
31 public class Loader {
32
33 static final boolean VERBOSE = true;
34
35 static final String REPOSITORIES = "loader.jar.repositories";
36 static final String MAIN_CLASS = "loader.main.class";
37
38 class RepositoryClassLoader extends URLClassLoader {
39
40 public RepositoryClassLoader(ClassLoader parent) {
41 super(new URL [0], parent);
42 }
43
44 public void addRepository(File repository) {
45 if (VERBOSE) System.out.println("Processing repository: " + repository);
46
47 if (repository.exists() && repository.isDirectory()) {
48 File [] jars = repository.listFiles();
49
50 for (int i = 0; i < jars.length; i++) {
51 if (jars[i].getAbsolutePath().endsWith(".jar")) {
52 try {
53 URL url = jars[i].toURL();
54 if (VERBOSE) System.out.println("Adding jar: " + jars[i]);
55 super.addURL(url);
56 } catch (MalformedURLException e) {
57 throw new IllegalArgumentException (e.toString());
58 }
59 }
60 }
61 }
62 }
63 }
64
65 public static void main(String [] args) throws Exception {
66 new Loader ().run(args);
67 }
68
69 void run(String [] args) throws Exception
70 {
71 String repositories = System.getProperty(REPOSITORIES);
72 if (repositories == null) {
73 System.out.println("Loader requires the '" + REPOSITORIES + "' property to be set");
74 System.exit(1);
75 }
76
77 String mainClass = System.getProperty(MAIN_CLASS);
78 if (mainClass == null) {
79 System.out.println("Loader requires the '" + MAIN_CLASS + "' property to be set");
80 System.exit(1);
81 }
82
83 if (VERBOSE) System.out.println("-------------------- Loading --------------------");
84
85 RepositoryClassLoader classLoader = new RepositoryClassLoader(this.getClass().getClassLoader());
86
87 StringTokenizer st = new StringTokenizer (repositories, File.pathSeparator);
88 while (st.hasMoreTokens()) {
89 classLoader.addRepository(new File (st.nextToken()));
90 }
91
92 Thread.currentThread().setContextClassLoader(classLoader);
93
94 if (VERBOSE) System.out.println("-------------------- Executing -----------------");
95 if (VERBOSE) System.out.println("Main Class: " + mainClass);
96
97 invokeMain(classLoader, mainClass, args);
98 }
99
100 void invokeMain(ClassLoader classloader, String classname, String [] args)
101 throws IllegalAccessException , InvocationTargetException , NoSuchMethodException , ClassNotFoundException
102 {
103 Class invokedClass = classloader.loadClass(classname);
104
105 Class [] methodParamTypes = new Class [1];
106 methodParamTypes[0] = args.getClass();
107
108 Method main = invokedClass.getDeclaredMethod("main", methodParamTypes);
109
110 Object [] methodParams = new Object [1];
111 methodParams[0] = args;
112
113 main.invoke(null, methodParams);
114 }
115 }
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Java API By Example, From Geeks To Geeks.