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Get a class from a jar gievn the className

Posted on 2011-09-20
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Last Modified: 2012-05-12
Hi Experts,
I need to create a method that  returns a class<?>  from a jarFile given a className :
Class<?>  getClassFromJar (JarFile jar, className){
      Return the Class / Null if not found
}
e.g.
Class<?> clazz = getClassFromJAr ( MyBundle.jar, “org.kal.os.factory.class”);
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Question by:bachra04
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9 Comments
 
LVL 47

Expert Comment

by:for_yan
ID: 36569215
You mean that this jar is not in your classpath ?

Otherwise you could use Class.forName(...)
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LVL 47

Expert Comment

by:for_yan
ID: 36569280
0
 
LVL 2

Author Comment

by:bachra04
ID: 36569281
Sorry not to be clear, the jar contains multiple classes including className

So the method will extract all classes and if the class

matches the given className, it returns it.
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LVL 47

Expert Comment

by:for_yan
ID: 36569285
This is how you can do it with JCL:

JarClassLoader jcl = new JarClassLoader();

  //Loading classes from different sources
  jcl.add("myjar.jar");
  jcl.add(new URL("http://myserver.com/myjar.jar"));
  jcl.add(new FileInputStream("myotherjar.jar"));
  jcl.add("myclassfolder/");

  //Recursively load all jar files in the folder/sub-folder(s)
  jcl.add("myjarlib/");

  JclObjectFactory factory = JclObjectFactory.getInstance();

  //Create object of loaded class
  Object obj = factory.create(jcl, "mypack.MyClass");

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LVL 47

Expert Comment

by:for_yan
ID: 36569295


So do you need this class for using it in the same code after you extract it?
Or you just need to extract it as a file?
0
 
LVL 47

Expert Comment

by:for_yan
ID: 36569303
If you need to use it in your code then
the above snippet from JCL shows how to create instance of such class
0
 
LVL 2

Author Comment

by:bachra04
ID: 36569318
I need to extract it as a file
0
 
LVL 47

Expert Comment

by:for_yan
ID: 36569393
To extract as a file - jar is just a zip file - so
the same way you extract it from zip file should work
0
 
LVL 47

Accepted Solution

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for_yan earned 2000 total points
ID: 36569400
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