JNI与Builder C ++

Question

I need to use the Java Native Interface (JNI) to communicate between my C++ application and my Java app.

I started with generating my JVM.Lib from my JVM.DLL . For that I used impdef and implib . I add my setting (Include path and Library path) in my project Builder C++.

However, my program generates

Error link JNI_CreateJavaVM.

How do I fix this error? How do I use JNI in my application Builder C++?

Answer 1

I succeed to fix this error.. I used Coff2Omf command to generate my lib

coff2omf jvm.lib jvm2.lib

After that, i added jvm2.lib and include path in my setting..

this is a sample C++ code to calling method java :

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

     #define PATH_SEPARATOR ';' /* define it to be ':' on Solaris */
     #define USER_CLASSPATH "." /* where Prog.class is */

     typedef /*_JNI_IMPORT_OR_EXPORT_*/ jint (JNICALL *JNI_CreateJavaVM_func)(JavaVM **pvm, void **penv, void *args);

     JNI_CreateJavaVM_func JNI_CreateJavaVM_ptr;

    JNIEnv* create_vm(JavaVM ** jvm)
    {
        JNIEnv *env;
        JavaVMInitArgs vm_args;
        JavaVMOption options;
        memset(&vm_args, 0, sizeof(vm_args));
        options.optionString = "-Djava.class.path=."; //Path to the java source code
        vm_args.version = JNI_VERSION_1_6; //JDK version. This indicates version 1.6
        vm_args.nOptions = 1;
        vm_args.options = &options;
        vm_args.ignoreUnrecognized = 0;

        HMODULE jvm_dll = LoadLibrary("C:\\Program Files (x86)\\Java\\jdk1.7.0_65\\jre\\bin\\server\\jvm.dll");

        /// You might check the GetLastError() here after the LoadLibrary()
        if(jvm_dll == NULL) 
        { 
            printf("can't load dll\n"); 
            exit(1); 
        }

        JNI_CreateJavaVM_ptr = (JNI_CreateJavaVM_func)GetProcAddress(jvm_dll, "JNI_CreateJavaVM");

        /// You might check the GetLastError() here
        if(JNI_CreateJavaVM_ptr == NULL) 
        { 
            printf("can't load function\n"); 
            exit(1); 
        }

        int ret = JNI_CreateJavaVM_ptr(jvm, (void**)&env, &vm_args);
        if(ret < 0) 
        { 
            printf("\nUnable to Launch JVM\n"); 
        }
        return env;
    }

    int main(int argc, char* argv[])
    {
        JNIEnv *env;
        JavaVM * jvm;
        env = create_vm(&jvm);

        if (env == NULL) { return 1; }
        jclass cls;
        jmethodID mid;
        jint square;
        jboolean not;
        cls = (*env).FindClass("Sample2");

        if(cls !=0)
          {   mid = (*env).GetStaticMethodID(cls, "intMethod", "(I)I");
                if(mid !=0)
                {  square = (*env).CallStaticIntMethod(cls, mid, 5);
                   printf("Result of intMethod: %d\n", square);
                }

                mid = (*env).GetStaticMethodID(cls, "booleanMethod", "(Z)Z");
                if(mid !=0)
                {  not = (*env).CallStaticBooleanMethod( cls, mid, 1);
                   printf("Result of booleanMethod: %d\n", not);
                }
          }

        int n = jvm->DestroyJavaVM();
        return 0;
    }