Hi,

I would like to know if it is possible to invoke a C# program using the .NET libraries from a Java application via JNI?
We have an exisiting Java application deployed over the web to client desktops (we bundle the jre along with the application). We have issues with the Java printing as it crashes the application when printing to certain printers. I would like to know if it would be possile to write a C# application that would be able to print - invoked from JNI. Would we have to bundle the .NET CLR along with the application to implement this?? As I do not have much exp with the .NET framework any help/suggestions would be highly appreciated.

thanks

 

 

Why C#???
Maybe you can make it in native code and then java app will call it, althougth you can call any app no matter the language

 

 

You may have trouble deploying a JNI solution over the web. e.g. applets

 

 

If is a program (not a library) then why do you just not run it via Runtime.exec()?

Anyways, the magazine "C/C++ Users Journal" has a commercial product advertised that provides a bridge between languages.

No idea if it works but you might want to look at it.

 

 

I would like to know the answer too.
In my case, I would like to use MSMQ from Java without using any commerical bridge.
I know there is C/C++ MSMQ API, but if JNI can use the .NET classes, the coding would be much much simpler to call the MSMQ .NET classes than calling the C/C++ MSMQ API.

 

 

I found the C# code much easier to use along with the .NET libraries - do not have much exposure to Win 32 api - programming :-( Anyways thanks for all your responses - I think I have found a work around to my problem by using SWT/JFace.

 

 

Here is an illustration of using JNI with MSMQ:
http://blogs.msdn.com/dotnetinterop/archive/2005/02/28/381735.aspx

 

 

Sure, you can do this. Writing the JNI code to bridge between Java and .NET can be pretty ugly, but there are third-party bridges like JNBridge (www.jnbridge.com) that encapsulate this and take care of it in a clean manner. Check it out and see if it does what you want.

 

 

Hi,

You should take a look at the J-Integra Interoperability suite.

http://j-integra.intrinsyc.com

They have several different products that would meet your needs in bridging java to .NET.

Cheers,
Adam

 

 

You can use the following API to run your .NET application via JNI.
Note, JVM and CLR co-existance in the same process is introduced in Java 6.0. I did not try to run it on the lower versions.

#include "windows.h"
#include "Oleauto.h"
#include "stdio.h"
#include "mscoree.h"
#import <mscorlib.tlb> raw_interfaces_only high_property_prefixes("_get","_put","_putref")

using namespace mscorlib;

WCHAR* createWCHAR( const char* szString ){
int nLength = strlen(szString)+1;
WCHAR* wszString = new WCHAR[nLength];
mbstowcs(wszString, szString, nLength);
return wszString;
}

...

char* szApplication="path"; // your .NET application
char* szVersion="v1.1.4322";// installed .NET version
char* szBuildFlavor="wks"; // "wks" or "svr"
char* szConfig=""; // path to the config file (if necessary)

WCHAR* wszApplication = createWCHAR(szApplication);
WCHAR* wszVersion = createWCHAR(szVersion);
WCHAR* wszBuildFlavor = createWCHAR(szBuildFlavor);
WCHAR* wszConfig = createWCHAR(szConfig);

CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);

ICorRuntimeHost* pHost = NULL;
IUnknown* pAppDomainThunk = NULL;
_AppDomain* pAppDomain = NULL;

HRESULT hr = CorBindToRuntimeHost( wszVersion, wszBuildFlavor, wszConfig, NULL,0,CLSID_CorRuntimeHost,IID_ICorRuntimeHost,(VOID**)&pHost);
if (FAILED(hr)) {
printf("CorBindToRuntimeHost error=%x\n", hr);
return -1;
}

hr = pHost->Start();
if (FAILED(hr)) {
printf("ICorRuntimeHost->Start error=%x\n", hr);
return -2;
}

hr = pHost->GetDefaultDomain(&pAppDomainThunk);
if (FAILED(hr)) {
printf("ICorRuntimeHost->GetDefaultDomain error=%x\n", hr);
return -3;
}

hr = pAppDomainThunk->QueryInterface(__uuidof(_AppDomain),(void**) &pAppDomain);
if (FAILED(hr)) {
printf("System::_AppDomain getting interface error=%x\n",hr);
return -4;
}

long lRet= 0;
// Execute the .NET assembly
hr = pAppDomain->ExecuteAssembly_2(_bstr_t(wszApplication), &lRet);
if (FAILED(hr)) {
printf("AppDomain::ExecuteAssembly_2 error=%x\n", hr);
ErrorDescription(hr);
return -5;
}

//lRet contains the exit code

CoUninitialize();

delete wszApplication;
delete wszVersion;
delete wszBuildFlavor;
delete wszConfig;


--Dmitry

 

 

It is not pretty, but you can also run your C# code in a Windows Service, and have it listen on a socket.

When the Java program wants to invoke the C# code, it opens a socket to localhost, writes the parameters as a String (or whatever format you want). The C# code reads the String from the socket, performs the operations, and sends a response over the socket connection, where the Java program receives it.

The advantage of this approach is that you don't need a third party package. The disadvantages are you need a Windows Service, you have to worry about security (e.g., the C# code should make sure the connection is from localhost), and performance (setting up a socket is probably slower than making a JNI call).