How to retrieve constants value from compiled code in jar file?
Hi everyone,
I've been looking for a way to solve this for a week now, without any much success... and I've finally decided to ask the Java gurus for a solution! :-)
Here's what I am basically trying to do:
I have several jar files in which there are only compiled code (.class).
In every class, there are 2 constants (declared as static final String) that I would like to retrieve (one is the version and the other the date of the last modification).
My goal is to print a list of all the classes in the jar files with the values of these 2 constants for each class.
The solution that I have right now to do this does not work properly: for now, I read all the elements of the classpath, check if these are jar files, and if so, I look into each one and load all the classes one by one and print the results.
The problem with this is that it uses the method Class.forName(className) and as some classes are unfortunately present in many jar files (2 or 3 copies), once the classes have been loaded, then it won't be "reloaded".
Without the possibility to "reload" these classes, I cannot see inconsistencies in the versions of the classes present in the jar files.
I have read many articles, and I thought that I could then use a custom classloader and create a new instance of this classloader for each jar file.
2 problems with this:
- according to many posts in the different forums I have read, the jar files should not appear in the CLASSPATH (but this would be easier for me if I could use it...)
- some classes will not be loaded if some classes (present in other jar files) are not loaded... and this makes things really really complicated to implement...
So, I thought that I was maybe doing this the wrong way, and that there might be an easy way out of this...
In fact, I do not need to load the classes... all I need to do, is take a sneak peek at the constants and print their values... and that's it!
Somehow, I think that this is possible to retrieve the values of compile time constants (declared as static final String) as I can see that with Eclipse (when opening a jar file).
So, my question is: how can I do that within my java application?
Or maybe there is another easier solution to do what I need?
Thanks in advance for your help!