RE: [Plplot-devel] How can java be told permanently about where to find libplplot(d)?

[Geoffrey F. <fu...@ga...>]

Alan W. Irwin writes:
 > On Mon, 12 Nov 2001, Geoffrey Furnish wrote:
 > 
 > > Alan W. Irwin writes:
 > >  > I agree there is nothing we can do with libplplot.  What I am asking is
 > >  > whether there is a mechanism *under java* (some additional command in
 > >  > PLStream.java or some javac option) which allows java to find libplplot (or
 > >  > any other C extension library) when it is installed in a non-standard place.
 > >  > I would be surprised and disappointed if java relied solely on
 > >  > LD_LIBRARY_PATH to solve this problem.
 > >
 > > Well, it's not anything special to java.  We're just talking about the
 > > semantics of dlopen(), which all programs use to load .so's.
 > 
 > >From what you have found out about dlopen, it looks like you can do anything
 > with it.  Thus, looking at this from the java level, java is free to do
 > anything before the low-level call to dlopen.  So it really becomes a
 > question of how java integrates the specification of library names using
 > System.loadLibrary with their treatment (if any) of the library path.
 > 
 > I did try your suggestion of using an absolute path as part of the library
 > name. (That is quite easy to do in a configurable way by making the
 > appropriate modification to config.java which in turn is accessed by the
 > System.loadLibrary call in PLStream.java.) Alas, this idea did not work. The
 > run time error was as follows:
 > 
 > Exception in thread "main" java.lang.UnsatisfiedLinkError: Directory
 > separator should not appear in library name:
 > /home/software/plplot_cvs/HEAD/plplot/tmp/plplotd

Yikes.

 > So apparently there is some name interpretation going on before the dlopen
 > call, and as part of that interpretation java insists the path must not be
 > part of the name specified to System.loadLibrary.

Well, that's pretty much a death knell (sp?) for your goal.

 > Of course, this still leaves wide open the question about whether there
 > might be some alternative mechanism in java to specify the path part of the
 > name since java can do anything it likes before the dlopen call. Thus, what
 > I am looking for is the java analog of the python sys.path.insert() function
 > that we use in pythondemos.py to manipulate the path where python looks for

I don't know of anything like that.

 > plmodules.so. Unfortunately, I am now stuck because I don't know how to
 > search for such functionality in the enormous number of java functions that
 > are available. Geoffrey, are you aware of a general site where I could
 > specify say "library path" as a search string and it would find all the java
 > functions that have something to do with the library path?  The java

All I have used is the java.sun.com site, which I suppose is the one
you're referring to.

 > tutorial does have a search engine so I tried that, but all it came up with
 > was the LD_LIBRARY_PATH idea.  I suppose it is possible that java has no way
 > to specify the library path other than LD_LIBRARY_PATH, but that is quite
 > limited compared to the sys.path.insert() function available for python.

I think this is where we say, "Welcome to the wonderful world of
Java."