use JNI to start JVM Builder C++

Question

in this post How to use JNI to start JVM in builder C++ application i converted jvm.lib from Coff to Omf. i used it to link JNI_CreateJavaVM() function. But it crash .

I used another code to start JVM from Builder C++ application. When i load the jvm.dll. It work!! the JVM is created when i load jvm in java directory but not when i copy this file(jvm.dll) in another directory and call it from this directory.Can you explain why i can't use a copy of jvm.dll to creat my JVM?

This is my Code :

JNIEnv *env;
JavaVMInitArgs vm_args;
JavaVMOption options;
memset(&vm_args, 0, sizeof(vm_args));

options.optionString = "-Djava.class.path=.;tika-app-1.5.jar;";
jint ii = GetVersion();

vm_args.version = JNI_VERSION_1_6;
vm_args.nOptions = 1;
vm_args.options = &options;
vm_args.ignoreUnrecognized = 0;
//String strPath = "C:\\Users\\mhechkel\\Documents\\RAD Studio\\Projects\\TestJVM\\Win32\\Debug\\jvm.dll";  
// when i copy jvm.dll in my application folder: It dosn't work!!!
String strPath = "C:\\Program Files (x86)\\Java\\jdk1.7.0_65\\jre\\bin\\server\\jvm.dll";

HMODULE jvm_dll = LoadLibrary(strPath.c_str()); //here it work fine!!

/// You might check the GetLastError() here after the LoadLibrary()
if(jvm_dll == NULL) 
{    
    Label1->Caption = "can't load dll"; 
}

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

 /// You might check the GetLastError() here
 if(JNI_CreateJavaVM_ptr == NULL)
 {
      Label1->Caption = "can't load function";
 }

 int ret = JNI_CreateJavaVM_ptr(jvm, (void**)&env, &vm_args);
 if(ret < 0)
 {
    Label1->Caption = "Unable to Launch JVM\n";
 }
 return env;

in this post stackoverflow.com/questions/7989502/… and in the ansewer n°1 he say it sould be the jvm in the ProgramFile\java\ director.. 1- Add the place where jvm.dll lies (should be in the program files\java\jsdk_*\bin\server) to the PATH environment variable on your windows machine.. IS This RIGHT??!! — BestHumain

apangin apangin · Accepted Answer · 2014-08-28T14:18:23

You'll need the complete JRE in order to create Java VM.
JVM will not start if does not find matching JRE at the place relative to jvm.dll path.

On Windows you can override the path where JVM looks for JRE using _ALT_JAVA_HOME_DIR environment variable, though this is a HotSpot internal option and is not guaranteed to work.

use JNI to start JVM Builder C++

1 Answers