Re: Installing Extensions to JREs properly
Dave Smith wrote:
I am trying to find the proper method for installing an extension into
a system's JRE for deploying an application I have written. The
The correct method to install extensions is: don't.
extension (RXTX, if it is relevant) contains one .jar file that needs
to be put into /lib/ext and two .dll files that need to be put into /
bin.
I can bundle the .jar file with my application to ensure that the
class files are always there, but how do I tell Java to keep the
two .dll files in the /bin/ directory every time it updates? Or, am I
trying to solve this problem the wrong way?
Steve W. Jackson wrote:
In my opinion, you are indeed going about it the wrong way. The jar an=
d
DLL files you want to use are part of your application, so you should
take full responsibility for their placement and then take proper steps
to ensure their use by your application.
Toward that end, there are a couple things that might be helpful.
First, look into the ways you can make the Java Extensions mechanism
work for you and what your options might be for putting files into
appropriate locations, or for perhaps telling the JVM to supplement
those locations with additional ones of your own choosing.
Secondly, the DLL files don't necessarily have to be put in the JRE's
own bin directory.
They necessarily have to be put somewhere other than the JRE's own bin
directory.
Consider installation of a regular .exe that requires its own DLLs.
If you are installing product Foo, would you put its DLLs in product
Bar's bin directory? Of course not; that would be silly.
The rules for locating JNI library files, assuming
that's what they are, vary by platform. But for Windows it's pretty
much the same as searching the PATH for executables. You can use that
knowledge to your advantage, but you could also simply load them from a
specific location using your own code rather than letting the system
find them for you. That is, rather than using System.loadLibrary and
letting it use the platform's own search method, you can use System.load
and force the loading of a DLL from a spot you specify.
Placing JAEs in the JRE extension directory is akin to placing DLLs in
the Windows System directory. It is the latter practice that gave
rise to the term "DLL hell".
Best practice is to restrict all application-specific artifacts to a
subdirectory of the application's own directory.
--
Lew