Set env var Java

flyz

I have a servlet on Solaris using JNI and I need to set the LD_LIBRARY_PATH for it to work.

What I want to do is set that variable from the servlet on startup.

I already set the java.library.path using :

System.getProperties().put("java.library.path","/usr/lib");

I've tried to use the same syntax to set the LD_LIBRARY_PATH :

System.getProperties().put("LD_LIBRARY_PATH", "/usr/lib");

which doesn't work.

I reckon I need to be able to export it as well which is where I'm having the problem.
From the command Line I do the following :

LD_LIBRARY_PATH=/usr/lib
export LD_LIBRARY_PATH

I've tried to do it this way :

Runtime.getRuntime().exec(new String [] {"export" , "LD_LIBRARY_PATH=/usr/lib"});

which gives me the following error :

java.io.IOException: export: not found
at java.lang.UNIXProcess.forkAndExec(Native Method)
at java.lang.UNIXProcess.<init>(UNIXProcess.java:54)
at java.lang.Runtime.execInternal(Native Method)
at java.lang.Runtime.exec(Runtime.java:550)
at java.lang.Runtime.exec(Runtime.java:475)
at java.lang.Runtime.exec(Runtime.java:441)

I've used the same syntax for deleting a folder before ( e.g. rm -rf folder)

grrrrr:(

deadl0ck

Why don't you set it before you start the servlet engine ?

I mean, why do you specifically neded to set it from the Java Code ?

flyz

Originally posted by deadl0ck
Why don't you set it before you start the servlet engine ?

I mean, why do you specifically neded to set it from the Java Code ?

I do that at the moment. But we ship the servlet to customers and I'm trying to make it as user friendly as possible.

deadl0ck

I don't think you need to go to that level of detail.

What you could do is get the current location that LD_LIBRARY_PATH points to and then look for a specific library (using File.exists()), that you know you need. If the library does not exist on any of the paths, the print an error message and exit. That way you can tell the user to set the library path - and you're not touching the enviornment

flyz

Originally posted by deadl0ck
I don't think you need to go to that level of detail.

What you could do is get the current location that LD_LIBRARY_PATH points to and then look for a specific library (using File.exists()), that you know you need. If the library does not exist on any of the paths, the print an error message and exit. That way you can tell the user to set the library path - and you're not touching the enviornment

Ah but I want to
The servlet is a background process. The customer should not have to so anything to configure it other than starting the server , tomcat in my case. There is no frontend to the servlet so I have nowhere to print out the error message, other than the log files.

I have a client application that connects to the server, that's the frontend. and I can't tell from there if the LD_LIBRARY_PATH is set or not.

Plus I'm using JNI remember so I install the library to '/usr/lib' .
So what I want to do is append the LD_LIBRARY_PATH.

Kev

export is a bash shell command not an executable program.

flyz

Originally posted by Kev
export is a bash shell command not an executable program.

Yeah I know , rm works if I do the following though:

Process ps = Runtime.getRuntime().exec(new String [] {"rm" , "-rf", ""+path+"data"});

deadl0ck

If it's the JNI libs you need, how do you know the customer will even have them ?

Shouldn't this be a pre-install step by the customer, to make sure he has the JNI stuff and sets LD_LIBRARY_PATH ?

I mean, it's a servlet on Tomcat, so will the JNI stuff be even guaranteed to be there ? Does it come with Tomcat ?
If so, you shouldn't have to export the LD_LIBRARY_PATH. If it doesn't come with tomcat then the customer needs JRE (or JDK) in the first place, so when they install that they should set the LD_LIBRARY_PATH

That being said, I still don't now how you do it .....

flyz

Originally posted by deadl0ck
If it's the JNI libs you need, how do you know the customer will even have them ?

That being said, I still don't now how you do it .....

I use Installanywhere to create my installation package.
I initiate the installation of the JDK followed by Tomcat followed by my servlet and my library.
It's as user friendly as I can get it.
The only thing that's missing is to automate setting the LD_LIBRARY_PATH to point to the library I install.

The library I'm referring to is my own library not a system library.

deadl0ck

Why not put the library file in the same location as the class that uses it.

./ is ususally on the LD_LIBRARY_PATH, any anyway, it should look in the same directory as where that class that loads it is...

flyz

Originally posted by deadl0ck
Why not put the library file in the same location as the class that uses it.

./ is ususally on the LD_LIBRARY_PATH, any anyway, it should look in the same directory as where that class that loads it is...

Well for one thing I can't guarantee that the LD_LIBRARY_PATH will be set. I'm presuming that the library path is to do with having an development environment. Which the customer isn't guaranteed to have.

I have never seen the LD_LIBRARY_PATH set on Solaris, I've always had to set it myself. And I have a development environment on my Solaris.

deadl0ck

Would it be possible to write a shell script to set the LD_LIBRARY_PATH, and then call that shell script with exec() ?

Kev

the environment variable would only exist for the shell that is run and any child processes that it spawns, so as soon as it exits the variable would disappear.

if your java program is executed from a shell script you could set the variable there, or for any exec() calls you make in java you can pass in any environment variables you want but i don't know any way of setting environment variables for jni.

davej

AFAIK there is no way for a java application to change it's own environment variables. This is a design decision by Sun. When you execute your servlet, it inherits the environment of the parent process. Even if you could get the export command to work using Runtime.getRuntime().exec (which by the way is possible) it would simply start a new child process and then terminate it again.

I suggest you wrap your servlet startup inside a script that sets the env variable first.

davej

flyz

Originally posted by davej
I suggest you wrap your servlet startup inside a script that sets the env variable first.

davej

Righteo that would solve my problems

thanks

Kev

Originally posted by davej
Even if you could get the export command to work using Runtime.getRuntime().exec (which by the way is possible)

how is it possible ?

davej

how is it possible ?

You need to use the exec (String [] cmdarray) method instead of the exec(String command) method.

This allows you to execute a command (first element of array) along with it's arguments (subsequent elements).

If you look at man bash you will see that there is a "-c string" option. Thus you can create a String array with 3 elements: "bash", "-c", "built-in-Command blah" and pass this to the exec method.


davej

Kev

but that won't have any effect so its not the same thing.