[HADOOP-10063] RunJar ClassLoader cached the class can't release

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.0.3, 2.2.0
• Component/s: util
• Assignee: Unassigned
• Reporter: Joe Au
• Created: 22/Oct/13 09:52
• Updated: 28/Oct/13 08:06

Description

At the end of method main()

RunJar.java

    ClassLoader loader =
      new URLClassLoader(classPath.toArray(new URL[0]));

    Thread.currentThread().setContextClassLoader(loader);
    Class<?> mainClass = Class.forName(mainClassName, true, loader);
    Method main = mainClass.getMethod("main", new Class[] {
      Array.newInstance(String.class, 0).getClass()
    });
    String[] newArgs = Arrays.asList(args)
      .subList(firstArg, args.length).toArray(new String[0]);
    try {
      main.invoke(null, new Object[] { newArgs });
    } catch (InvocationTargetException e) {
      throw e.getTargetException();
    }

The ClassLoader cached the class can't release.Because the development time class code will often changes, so will be very inconvenient.

Rewrite as follows:

RunJar.java

		ClassLoader prevCl = Thread.currentThread().getContextClassLoader();
		ClassLoader loader = new URLClassLoader(classPath.toArray(new URL[0]), prevCl);

		try {
			Thread.currentThread().setContextClassLoader(loader);

			Class<?> mainClass = Class.forName(mainClassName, true, loader);
			Method main = mainClass.getMethod("main", new Class[] { Array
					.newInstance(String.class, 0).getClass() });
			String[] newArgs = Arrays.asList(args).subList(firstArg, args.length)
					.toArray(new String[0]);
			
			main.invoke(null, new Object[] { newArgs });
		} catch (InvocationTargetException e) {
			throw e.getTargetException();
		} finally {
			// Restore
			Thread.currentThread().setContextClassLoader(prevCl);
		}