Use JNI twice : Unable to create JVM
I want to use a java method to call an C++ method, and in that C++ method another java method is called. Then i use two types of JNI together and found this problem.
If i use the java method to call the C++ method, or use the C++ method to call the other java method , it is alright.
--
This is a simple test :
I use the native method "call()" in "Mosquito.java" to call method "Java_Mosquito_call" in main.cpp. In that method i use "myWindow()" to call the main method in WindowDemo.java.
Mosquito.java :
publicclass Mosquito{
publicnativevoid call();
static{
System.loadLibrary("mosquito");
}
publicstaticvoid main(String argsp[]){
new Mosquito().call();
}
}
main.cpp :
#include <iostream.h>
#include <string.h>
#include"Frog.h"
#include"Mosquito.h"
JNIEXPORTvoid JNICALL Java_Mosquito_call
(JNIEnv *env, jobject obj)
{
Frog f;
f.prt();
f.myWindow();
}
Frog.h :
#include <iostream.h>
#include <string.h>
#include <jni.h>
class Frog{
public :
void prt()
{
cout <<"This is class Frog !\n" << endl;
}
public :
void myWindow()
{
JNIEnv *env;
JavaVM *jvm;
JavaVMInitArgs vm_args;
JavaVMOption options[1];
jint java_error;
jclass java_class;
jmethodID java_method;
jstring jstr;
jobjectArray args;
options[0].optionString ="-Djava.class.path=.";
options[0].extraInfo = NULL;
memset (&vm_args,0,sizeof(vm_args));
vm_args.version = JNI_VERSION_1_4;
vm_args.nOptions = 1;
vm_args.options = options;
java_error = JNI_CreateJavaVM(&jvm, (void **) &env, &vm_args);
if(java_error < 0)
{
cout <<"ERROR: Unable to create JVM\n" << endl;
}
java_class = env->FindClass("WindowDemo");
if(java_class == NULL)
{
cout <<"ERROR: Unable to find class 'WindowDemo'\n" << endl;
}
java_method = env -> GetStaticMethodID(java_class,"main","([Ljava/lang/String;)V");
if (java_method == NULL)
{
cout <<"error finding 'main' method\n" << endl;
}
env -> CallStaticVoidMethod(java_class,java_method,NULL);
jvm -> DestroyJavaVM();
}
};
I also test to use "JNI_CreateJavaVM()" twice in one C++ file.And the seccond will failed.
