覆盖rt.jar中的单个类

Question

I'm looking for a neat way to override a class from the bootstrap class path, rt.jar . The reason is OpenJDK7 bug http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7104625

The fix for this bug is a trivial (see linked mailing list post) change to sun.awt.X11.XComponentPeer . So I was wondering if there is an easy way to override just this one affected class on my classpath, without having to repack/rebuild rt.jar (so the fix isn't lost on the next automatic update of OpenJDK).

Ideally, it would also affect Eclipse...

I assume that java -Djava.system.class.loader=myClassLoader would work? Is there any other way to override a single class with such a "hotfix"? (Note: not used in my own code, but deep in Java AWT code)

Answer 1

您可以使用VM参数-Xbootclasspath/p将带有修补类的自己的JAR文件添加到引导类路径。

Answer 2

I believe the only supported way of doing this is to "patch" rt.jar by replacing the desired *.class file. 7-Zip can help you easily do this.

This is exactly how Oracle supplied their double-parsing bug fix with their FPUpdater tool, which was essentially a script that did just this. ( Some history .)

Answer 3

我认为您可以尝试使用javaagent当JVM加载系统类并将其交换到您的系统类时，您必须拦截事件

Answer 4

I think @ziesemer is correct, but you may be able to use the classloader to replace the offending class when your app is bootstrapping. This may be cleaner if you don't want to worry about the JDK updating underneath you, though you'd have to stick this bootstrapping classloader code into every app you are working on.