在Raspberry Pi上从C ++代码调用Java类

Question

I am doing a C++ program on my Raspberry Pi and I want to call a Java class from my C++ program.

I have my main program written in C++, which is the driver for my application, however, I am trying to interface with a device through my program and the communication API is written in Java. I don't want to rewrite the entire API, so my main objective is to call the API from my C++ main.

Does anyone know how this is possible?? I heard JNI is one way but I am uncertain how to accomplish this on RPI.

Answer 1

It can be done with JNI. As it happens I have a project on GitHub where I have been working on a C++ wrapper generator for Java.

https://github.com/wshackle/java4cpp

Even if you don't want to use it, some of the code or examples might be useful to take a look at.

To compile a JNI program on linux ( which I think should also work for Rasberry PI although I have never used a Rasberry PI) , I would use a command of the form:

export JAVA_HOME=/usr/local/jdk1.8.0_60
g++ -I ${JAVA_HOME}/include -I ${JAVA_HOME}/include/linux -L ${JAVA_HOME}/jre/lib/i386/server/  -Wl,--rpath ${JAVA_HOME}/jre/lib/i386/server/  cpplussource.cpp -ljvm -o newprogram

I am not sure which processor the Rasberry-PI uses. i386 might be replaced with something else. Your JDK might come with a client directory rather than a server directory.

There is more on the C++ compiler options at :

https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/design.html#compiling_loading_and_linking_native_methods

and more on invoking the virtual machine at:

https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/invocation.html#overview