How to convert a jar into so file and use it ?

[Andrew Haley]

David Michel wrote:
>
> I have a very simple java test code that uses a public method called
> 'coucou' of a external jar called 'Hello.jar' which contains the
> package 'hello' and the public class 'Hello'. Here is the test code
> Tool.java:
> 
> import hello.Hello;
> 
> public class Tool
> {
>    public static void main(String[] args)
>    {
>      System.out.println("main program running");
>      Hello.coucou();
>    }
> }
> 
> which I would usually compile, with the following commands:
> 
> $ gcj -O0 -g0  -C Tool.java --classpath=./:extern/Hello.jar
> $ gij -cp .:extern/Hello.jar Tool
> 
> Now if I want to compile Tool.java natively with gcj, what do I need to do ?
> 
> I can create the shared library from the jar like this:
> $ gcj -O0 -g0  -shared -findirect-dispatch -fjni -fPIC
> extern/Hello.jar -o extern/Hello.jar.so
> 
> 
> I can then compile Tool.java into Tool.o with:
> $ gcj -O0 -g0  --classpath=./:extern/Hello.jar  -c Tool.java -o Tool.o
> 
> (altough this is using the jar and not the so ??)
> 
> But then, I'm stuck with creating the final executable, i.e. Tool.out

You didn't provide the source code for hello.Hello.  However, I'm
guessing it's

public class Hello
{
  public static void coucou()
  {
    System.out.println("coucou");
  }
}


 $ gcj -C hello/Hello.java
 $ jar cf Hello.jar hello/Hello.class
 $ gcj -shared hello/Hello.class -o libhello.so -fpic
 $ gcj Tool.java -L. -lhello --classpath=.:hello/Hello.jar --main=Tool
 $ LD_LIBRARY_PATH=. ./a.out
main program running
coucou


Or, with -findirect-dispatch

 $ gcj -shared hello/Hello.java -o libhello.so -fpic -findirect-dispatch
 $ gcj Tool.java -L. -lhello --classpath=.:hello/Hello.jar --main=Tool -findirect-dispatch

Andrew.