如何在Java运行时重载类

Question

It's possible to add modified classes to a jar file manually, but to make it simple I want to do it on runtime.

Lets put it this way:

JAR_A.jar - contains A.class and B.class

JAR_B.jar - contains modified version of B.class

Instead of adding the modified B.class manually with an archive manager I want to accomplish the same on runtime.

Answer 1

http://www.java2s.com/Code/Java/File-Input-Output/CreateJarfile.htm

 FileOutputStream fout = new FileOutputStream("c:/tmp/foo.jar");
 JarOutputStream jarOut = new JarOutputStream(fout);
 jarOut.putNextEntry(new ZipEntry("com/foo/")); // Folders must end with "/".
 jarOut.putNextEntry(new ZipEntry("com/foo/Foo.class"));
 jarOut.write(getBytes("com/foo/Foo.class"));
 jarOut.closeEntry();
 jarOut.putNextEntry(new ZipEntry("com/foo/Bar.class"));
 jarOut.write(getBytes("com/foo/Bar.class"));
 jarOut.closeEntry();
 jarOut.close();
 fout.close();