How to use JNI in a multithreaded environment_ CreateJavaVm(C)

I am working in JNI using C as my mother tongue I can create (c) shared libraries, and I can call Java functions with the help of shared libraries

Steps involved in my process:

1) Using JNI_ Createjavavm create VM [IN C]

2) Use the VM created for processing

3) Exit thread

If I will perform the same process again, JNI_ Createjavavm does not create any VMS, and it returns the JNI error code as - 1 (unknown error) Then I check that getcreatedjavavms returns 0, and I try to get env getenv. It crashes

I also tried the getjavavm function, but it is crashing with an error message,

#
# A Fatal error has been detected by the Java Runtime Environment:
#
#  SIGSEGV (0xb) at pc=0x00c1b3ed,pid=8645,tid=2961177456
#
# JRE version: 7.0_25-b15
# Java VM: Java HotSpot(TM) Server VM (23.25-b01 mixed mode linux-x86 )
# Problematic frame:
# C  [libVsphere.so+0x6a3ed]  _Jv_jnienv::GetJavaVM(_Jv_JavaVM**)+0xb

Why and how to solve this problem?

How to use JNI in a multithreaded environment_ CreateJavaVm,JNI_ Getcreatedvms and getjavavm

Solution

You should only create a JavaVM global instance at the beginning of the program in a thread:

/* Global instance */
JavaVM *jvm;

int main() {
/* ...call to JNI_CreateJavaVm ...*/
}

Then, on each thread, if you want to get the Java environment, you should use the global pointer (JVM) to the Java machine:

jnienv *env;
(*jvm)->AttachCurrentThread(jvm,(void **)&env,NULL);

Finall can access methods / classes, etc. using this environment:

jclass ex = (*env)->FindClass(env,"java/lang/NullPointerException");