Java api in .Net (JavaIntrop)

In my previous blog I have said something about using a java library in .Net . My case demanded me to use a java library in .Net . Many times we find  a decent and clean library to use but its a java library and some time we find a java library that is impossible to ignore , in that case we hope for a way to use java api in .Net . I roamed the net and tried the fit and that fit happened to fit my case.  That is IKVM.Net by Jeroen Frijters .

http://www.ikvm.net/index.html

IKVM.net is a open source  java implementation , that comes with the OpenJdk  implementation  in .Net and various tools to interop between  java and .Net  . Whole JVM is implemented in  .Net and its very easy to convert java jar files to .Net assemblies and .Net assemblies to java  jars (interface and stub classes ).

Taking on my case to convert java jar files to .Net assemblies , there comes a command line utility with IKVM called ikvmc.exe . To generate the .Net assembly for a jar file we first specify the command line switch [-target:library] for generating  a dll .  Without this command line switch ikvmc.exe will generate a exe for a jar file if it encounters a main method in a class.  On command prompt we change directory to IKVM binaries folder and specify command :

C:\IKVM>ikvmc.exe –target:library  hapi-base-1.2.jar

The jar file is in same directory as ikvm binaries , this will generate the hapi-base-1.2.dll . There will be many warnings by ikvmc.exe of noclassdeffound  , this is because we haven’t specified the dependency dll’s. IKVM comes with the OpenJdk implementation in .Net and they are in form of dll’s. Now we have to specify the OpenJdk dll’s that our jar file depends upon to rectify the warnings.

C:\IKVM>ikvmc.exe –target:library  hapi-base-1.2.jar –reference:IKVM.OpenJDK.Core.dll  -reference:IKVM.OpenJDK.Util.dll

In example I have only referenced some of OpenJdk dll’s , but we have to reference all the dll’s that our jar file depends upon.  Upon completion of the command a hapi-base-1.2.dll will be generated . Now moving on to next jar file (hapi-structures-v21-1.2.jar).

C:\IKVM>ikvmc.exe –target:library  hapi-structures-v21-1.2.jar –reference:IKVM.OpenJDK.Core.dll  -reference:IKVM.OpenJDK.Util.dll

As this new jar file have dependency on previous jar file , we have to reference the dll of previous jar file to make a successful porting of this jar file to a dll.

C:\IKVM>ikvmc.exe –target:library  hapi-structures-v21-1.2.jar –reference:hapi-base-1.2.dll  –reference:IKVM.OpenJDK.Core.dll  -reference:IKVM.OpenJDK.Util.dll

And so on we can create dll’s from jar files resolving the dependency using the [-reference:<dllname>] .Now these dll’s are ready to be used in your .Net project . We have to at least add reference of IKVM.Runtime.dll in our project and other OpenJdk dll’s that out converted jar dll’s depend upon.  Keep on porting .