Embed Java VM in Executables using Java Native Interface (JNI)

Here InvokeJVM.C which illustrates some calls in JNI. Please ensure that you are compiling in a multithreaded environment and with JDK117B or JDK12 Header files.

#include <jni.h>
#include <windows.h>

#define PATH_SEPARATOR ';' /* platform dependent */
#define USER_CLASSPATH "." /* directory where Sample.class is present */

typedef jint (*P_JNI_GetDefaultJavaVMInitArgs)(void *args);
typedef jint (*P_JNI_CreateJavaVM)(JavaVM **pvm, JNIEnv ** penv, void *args);

void __cdecl main(int argc, char **argv) {
    char classpath[1024];           /* Class Path */
    JNIEnv          *env = NULL;    /* Environment */
    JavaVM          *jvm = NULL;    /* Virtual Machine */
    JDK1_1InitArgs  vm_args;        /* Initializing arguments */
    jint            res = -1;
    jclass          cls;
    jmethodID       mid;
    jstring         jstr;
    jobjectArray    args;
    HANDLE          hLib = NULL; 

    /* Pointer to required functions */
    P_JNI_GetDefaultJavaVMInitArgs pfnGetDefaultJavaVMInitArgs = NULL;
    P_JNI_CreateJavaVM             pfnCreateJavaVM = NULL;

    if(argc < 3){
        printf("Usage : InvokeJVM <javai.dll> <Sample>\n");
        exit(-1);
    }

    /* Load the library */
    printf("Loading Library .... <%s>\n",argv[1]);
    hLib = LoadLibrary(argv[1]);

    if(hLib == NULL) {
        printf("Unable to Load Library.... exitting....");
        exit(-1);
    }

    /* Store the function pointer for getting default arguments */
    pfnGetDefaultJavaVMInitArgs = (P_JNI_GetDefaultJavaVMInitArgs) GetProcAddress(hLib, "JNI_GetDefaultJavaVMInitArgs");

    /* IMPORTANT: specify vm_args version # if you use JDK1.1.2 and beyond */
    vm_args.version = 0x00010001;

    /* Get the default arguments */
    if(pfnGetDefaultJavaVMInitArgs != NULL)
        (*pfnGetDefaultJavaVMInitArgs)(&vm_args);

    /* Append USER_CLASSPATH to the end of default system class path */
    if(vm_args.classpath != NULL)
        sprintf(classpath, "%s%c%s", vm_args.classpath, PATH_SEPARATOR, USER_CLASSPATH);
    else 
        sprintf(classpath, "%s", USER_CLASSPATH);
    
    vm_args.classpath = classpath;

    /* Store the function pointer for creating the VM */
    pfnCreateJavaVM = (P_JNI_CreateJavaVM) GetProcAddress(hLib, "JNI_CreateJavaVM");

    /* Create the Java VM */
    if(pfnCreateJavaVM != NULL)
        res = (*pfnCreateJavaVM)(&jvm,&env,&vm_args);
    if (res < 0) {
        fprintf(stderr, "Can't create Java VM\n");
        exit(1);
    }

    /* Find the class that we need to use */
    cls = (*env)->FindClass(env, argv[2]);
    if (cls == 0) {
        fprintf(stderr, "Can't find %s.class\n",argv[2]);
        exit(1);
    }
 
    /* get a id to the "main" method */
    mid = (*env)->GetStaticMethodID(env, cls, "main", "([Ljava/lang/String;)V");
    if (mid == 0) {
        fprintf(stderr, "Can't find main function in %s.class\n",argv[2]);
        exit(1);
    }

    /* create a new string to pass as parameter */
    jstr = (*env)->NewStringUTF(env, "Hello World!!!");
    if (jstr == 0) {
        fprintf(stderr, "Out of memory\n");
        exit(1);
    }

    /* create a new array */
    args = (*env)->NewObjectArray(env, 1, (*env)->FindClass(env, "java/lang/String"), jstr);
    if (args == 0) {
        fprintf(stderr, "Out of memory\n");
        exit(1);
    }
    
    /* Ready to rock'n'roll */
    (*env)->CallStaticVoidMethod(env, cls, mid, args);

    /* All's well that ends well */
    (*jvm)->DestroyJavaVM(jvm);
}

Here is a Sample.java file which has a main() function.

import java.lang.*;
import java.io.*;

/* Sample Class does nothing. It just prints its arguments */
public class Sample
{
    static public void main (String argv[])
    {
        System.out.println(">>>> Java Version : " + System.getProperty("java.version"));
        System.out.println(">>>> Java Vendor  : " + System.getProperty("java.vendor"));
        System.out.println(">>>> Sample.class started successfully with " + argv.length + " argument(s)");
        for(int i=0;i<argv.length;i++)
           System.out.println(">>>> args ["+i+"] : " + argv[i]);
    }
}

Set the PATH, CLASSPATH as follows and then use InvokeJVM

JDK12
SET PATH=D:\JDK1.2\BIN;D:\JDK1.2\JRE\BIN\CLASSIC;
SET CLASSPATH=.;
INVOKEJVM jvm Sample

JDK117B
SET PATH=D:\JDK1.1.7B\BIN;
SET CLASSPATH=D:\JDK1.1.7B\LIB\CLASSES.ZIP;.;
INVOKEJVM javai Sample

JDK116
SET PATH=D:\JDK1.1.6\BIN;
SET CLASSPATH=D:\JDK1.1.6\LIB\CLASSES.ZIP;.;
INVOKEJVM javai Sample

IE - If you have installed the latest Microsoft VM
SET PATH=C:\WINNT40\SYSTEM32;
SET CLASSPATH=.;
INVOKEJVM msjava Sample

Sample Output for JDK1.1.7B
Loading Library .... 
>>>> Java Version : 1.1.7B
>>>> Java Vendor  : Sun Microsystems Inc.
>>>> Sample.class started successfully with 1 argument(s)
>>>> args [0] : Hello World!!!

More Information

JDK 1.1 JNI - Java Native Interface Specification

Download demo project - 9 KB

Date Last Updated: April 3, 1999