calling java function from c using jni

Question

I'm writing a simple program to call a Java function from my C program.

Following is my code:

#include <jni.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <pthread.h>
#include <time.h>
#include <stdlib.h>

JNIEnv* create_vm() {
    JavaVM* jvm;
    JNIEnv *env;
    JavaVMInitArgs vm_args;

    JavaVMOption options[1];

    options[0].optionString - "-Djava.class.path=/home/chanders/workspace/Samples/src/ThreadPriorityTest";
    vm_args.version = JNI_VERSION_1_6;
    vm_args.nOptions = 1;
    vm_args.options = &options;
    vm_args.ignoreUnrecognized = JNI_FALSE;

    JNI_CreateJavaVM(&jvm, (void**)&env, &vm_args);
    return env;
}

void invoke_class(JNIEnv* env) {
    jclass helloWorldClass;
    jmethodID mainMethod;
    jobjectArray applicationArgs;
    jstring applicationArg0;

    helloWorldClass = (*env)->FindClass(env, "InvocationHelloWorld");
    mainMethod = (*env)->GetStaticMethodID(env, helloWorldClass, "main", "([Ljava/lang/String;)V");

    applicationArgs = (*env)->NewObjectArray(env, 1, (*env)->FindClass(env, "java/lang/String"), NULL);
    applicationArg0 = (*env)->NewStringUTF(env, "From-C-program");
    (*env)->SetObjectArrayElement(env, applicationArgs, 0, applicationArg0);
    (*env)->CallStaticVoidMethod(env, helloWorldClass, mainMethod, applicationArgs);
}

int main() {
    JNIEnv* env = create_vm();
    invoke_class(env);
}

I'm compiling the above program using: gcc -o invoke -I$JAVA_HOME/include/ -I$JAVA_HOME/include/linux -L$JAVA_HOME/jre/lib/amd64/server/ ThreadPriorityTest.c

and i'm getting the following error:

/tmp/ccllsK5O.o: In function `create_vm': ThreadPriorityTest.c:(.text+0x35): undefined reference to `JNI_CreateJavaVM' collect2: ld returned 1 exit status

I'm not really sure what is causing this problem

UPDATE 1

Included the -ljvm in the command line and then got a undefined reference to FUNCTION_NAME I'm running it on Rhel 6.2

Answer 1

You've got the path to the Java library (the -L option), but not the library itself. You need to include -ljvm on the link line as well.