Question

I am trying to make a callback interface between C# and Java using JNA.

C# <–CLI–> Visual C++ 2010 <–JNA–> Java

Between Java and C++ I am using unmanaged structures to get callback functionality. In C++ I am trying to wrap structure, that has callback pointers, into managed object.

Between Java and C++ everything works until I’m trying to use gcroot for managed object generation in unmanaged code.

UPDATE it even fails without gcroot. Just with “Logger^ logger = gcnew Logger(logStruct);”

My current solution is as follows:

Java

LoggerStruct.java

package jnatest;

import com.sun.jna.Callback;
import com.sun.jna.Structure;
import java.util.logging.Logger;

public class LoggerStruct extends Structure {
    private Logger logger;

    public interface GetLevelCallback extends Callback {
        int callback();
    }

    public GetLevelCallback getLevel;

    public LoggerStruct(Logger log) {
        super();
        this.log = log;

        getLevel = new GetLevelCallback() {
            public int callback() {
                return logger.getLevel().intValue();
            }
        }

        setFieldOrder(new String[] {"getLevel"});
    }
}

ITestLib.java

package jnatest;

import com.sun.jna.Library;
import com.sun.jna.Native;

public interface ITestLib extends Library {
    ITestLib INSTANCE = (ITestLib) Native.loadLibrary("JNATestC", ITestLib.class);
    int callbackTest(LoggerStruct logStruct);
}

Main.java

package jnatest;

import com.sun.jna.NativeLibrary;
import java.util.logging.Logger;
import java.util.logging.FileHandler;

public class MainClass {
    public static void main(String[] args) throws Exception  {
        NativeLibrary.addSearchPath("JNATestC", "C:\\JNATest");

        Logger log = Logger.getLogger("Test");
        FileHandler fileTxt = new FileHandler("Logging.txt");
        log.addHandler(fileTxt);

        LoggerStruct logStruct = new LoggerStruct(log);

        ITestLib.INSTANCE.callbackTest(logStruct);
    }
}

C++

JNATestC.h

#pragma once

extern "C" {
    struct LoggerStruct {
        int (*getLevel)();
    }
    __declspec(dllexport) void callbackTest(LoggerStruct * logStruct);
}

namespace JnaWrapperTypes {
    public ref class Logger { // "public ref" because I have to use it in C# as well
        private:
            LoggerStruct * logStruct;
        public:
            Logger(LoggerStruct * logStruct);
            ~Logger() {} 
            int getLevel();
    };
}

JNATestC.cpp

#include "stdafx.h"
#include <vcclr.h>
#include "JNATestC.h"

namespace JnaWrapperTypes {
    Logger::Logger(LoggerStruct * logStruct) {
        this->logStruct = logStruct;
    }
    Logger::getLevel() {
        return logStruct->getLevel();
    }
}

using namespace JnaWrapperTypes;
using namespace StaticCSharpNamespace; // Just an example. Not existing C# lib.

extern "C" {
    __declspec(dllexport) void callbackTest(LoggerStruct * logStruct) {
        int level = logStruct->getLevel();

        gcroot<Logger^> logger = gcnew Logger(logStruct); // IF I ADD "gcroot" FOR "Logger" THEN WHOLE INVOKE FAILS
        level = logger->getLevel();

        StaticCSharpClass::staticMethod(logger); // I want to pass Managed object to C# later

        gcroot<System::String^> str = gcnew System::String(""); // This doesn't generate error
    }
}

I wrote these on the fly. I hope these validate as well.

What am I doing wrong? For example if I use…

gcroot<System::String^> str = gcnew System::String("");

…everything works just fine.

Is there another way to pass managed object to C#?

Log for this error LOG

UPDATE

It seems that anykind of my own Class usage will head me to failure.

UPDATE

Anykind of my own Managed object or function use heads me to failure.

UPDATE

StaticCSharpClass::staticMethod(); fails as well. Looks like all operations related to Managed objects fail.

UPDATE

If I invoke the same method from .NET, everything works fine.

just to make this problem more findable
Internal Error (0xe0434352)

Answer 1

Should have googled for error “Internal Error (0xe0434352)”.

http://jira.talendforge.org/browse/TDI-19427

It leads to point that I have to register the dll for GAC (Global Assembly Cache), because Java searches only GAC and Application Base directories for dll. And because Java.exe paths aren’t configurable.

== Solution ==

Use post build event to register assembly for GAC:

gacutil /i "$(TargetPath)"

Great monologue! =)