Java HotSpot Virtual Machine

Hi, i am a newbie to native methods. Previous method tries to take the javastring, converts to BSTR and passes it to a visual basic application. Encoding is important and it must support non UTF-8 characters. The problem is that it passes only first character of all string. I couldn't comment where the problem is. Thanks in advance...

BSTR _stdcall getMessageAsText(){
	jmethodID id = env->GetMethodID(testClass, "checkSendingTextMessage", "()Ljava/lang/String;");
	jstring strJava = (jstring) env->CallObjectMethod( testObject, id );
	
	BSTR retValue = NULL;
	env->ExceptionDescribe();
	
	if (strJava != NULL){
		jboolean isCopy = 0;
		const jchar *data = env->GetStringChars(strJava, &isCopy);
		int length = env->GetStringLength(strJava);
		char* rtn = (char *)malloc( length*2+1 );
		int size = 0;
		size = WideCharToMultiByte( CP_ACP, 0, (LPCWSTR)data, length, rtn, (length*2+1), NULL, NULL );
		if( size <= 0 )
			return NULL;
		retValue = ::SysAllocString((WCHAR *)data);
		if (!isCopy)
			env->ReleaseStringChars(strJava,data);
		
		return retValue;
	}

	return NULL;
}