从Eclipse导出的JAR文件与可运行的JAR文件中的行为不同

Question

I'm getting different results from the code below depending upon whether I select JAR file or Runnable JAR file from Eclipse's File|Export dialog:

public static void main(String[] args) throws IOException {
    Enumeration<URL> dirs = Thread.currentThread().getContextClassLoader().getResources(
                "com/test/pojo");
    System.out.println(dirs.hasMoreElements());
}

If I choose:

• JAR file - the code above prints false
• Runnable JAR file - the code above prints true

I compared the contents of JARs exported both ways, and the files in them are exactly the same!

Can anyone explain what's going on here?

Answer 1

I'm not sure of my answer, but I'll try : your files are maybe the same, but it's doesn't imply that the meta-data of the files are the same, ie you can have to different files (eg in different format) but containing the same data. So maybe the meta-data of Runnable JAR and JAR are different (and it wouldn't be surprising).

Answer 2

Problem solved!ClassLoader.getResources() will load the classes in my jar, but none-runnable jar didn't maintain the correct directory enties.

Runnable-JAR:

jar tf hall1.jar
META-INF/MANIFEST.MF
  com/
  com/test/
  com/test/Main.class
  com/test/pojo/
  com/test/pojo/Pojo.class

None-Runnable JAR:

jar tf hall1.jar
  META-INF/MANIFEST.MF
  com/test/Main.class
  com/test/pojo/Pojo.class

So all I have to do is selecting "Options-Add directory entries" in JAR-Export pannel