An unexpected error has been detected by HotSpot Virtual Machine:

[Nandhini Venugopal]

Hi,
I'm new to JNI programs.. I'm trying to do a JNI program.. In that i'm getting "An unexpected error has been detected by HotSpot Virtual Machine:" error while running the code..
Can any one figure out the problem.?

My Jave code
FieldAccess.java

public class FieldAccess {

public static void main(String args[]) {

next[] Nxt;
next n=new next();
System.out.println(n.g);
Nxt=n.arrayFields();
System.out.println("In Java");
}

static {
System.out.println("Hello");
System.loadLibrary("FieldAccess");



}

}

next.java

public class next{
public String g;
public String h="hi";

public native next[] arrayFields();
static {
System.out.println("Hello");
System.loadLibrary("FieldAccess");



}

}


FieldAccess.c

#include <stdio.h>

#include <jni.h>

#include "next.h"
JNIEXPORT jobjectArray JNICALL Java_next_arrayFields
(JNIEnv *env, jobject jobj){

jobjectArray ret;
int i,j;
printf("Hello");
jclass cls = (*env)->FindClass(env,"/usr/jnieg/next");
printf("Hello");
ret= (jobjectArray)(*env)->NewObjectArray(env,10,cls,NULL);
printf("Hello");
if(ret==NULL){
ret=NULL;
}
for(i=0;i<10;i++)
{
jobject remoteNode = (*env)->AllocObject(env,cls);
if (remoteNode == NULL)
{
ret = NULL;
}
jfieldID fid;
fid = (*env)->GetFieldID(env,cls, "g", "Ljava/lang/String;");
if (fid == NULL)
{
ret = NULL;
}
(*env)->SetObjectField(env,remoteNode, fid, (*env)->NewStringUTF(env,"Hello"));
(*env)->SetObjectArrayElement(env,ret, i, remoteNode);
printf("%s",remoteNode);
}
printf("Hello");
return ret;


}

[fred rosenberger]

I put your source into code tags. See how it is much easier to read? Also, can you tell us the EXACT and COMPLETE error message you get? Most folks here are not going to be able to compile and debug the C code, so without that information we're only kind of guessing. (this assume you didn't - I have no idea what an error like this would actually look like).

FieldAccess.java

public class FieldAccess {

public static void main(String args[]) {

next[] Nxt;
next n=new next();
System.out.println(n.g);
Nxt=n.arrayFields();
System.out.println("In Java");
}

 static {
	System.out.println("Hello");
   System.loadLibrary("FieldAccess");

 

  }

}

next.java

public class next{
public String g;
public String h="hi";

public native next[] arrayFields();
static {
	System.out.println("Hello");
   System.loadLibrary("FieldAccess");

 

  }

}

FieldAccess.c

#include <stdio.h>

#include <jni.h>

#include "next.h"
JNIEXPORT jobjectArray JNICALL Java_next_arrayFields
  (JNIEnv *env, jobject jobj){

	jobjectArray ret;
	int i,j;
	printf("Hello");
	jclass cls = (*env)->FindClass(env,"/usr/jnieg/next");
	printf("Hello");
	ret= (jobjectArray)(*env)->NewObjectArray(env,10,cls,NULL);
	printf("Hello");
	if(ret==NULL){
	ret=NULL;
	}
        for(i=0;i<10;i++)
	{
	jobject remoteNode = (*env)->AllocObject(env,cls);
	if (remoteNode == NULL)
    	{
    		ret = NULL;
		}
        jfieldID fid;
	fid = (*env)->GetFieldID(env,cls, "g", "Ljava/lang/String;");
	if (fid == NULL)
    	{
    		ret = NULL;
		}
	(*env)->SetObjectField(env,remoteNode, fid, (*env)->NewStringUTF(env,"Hello"));
	(*env)->SetObjectArrayElement(env,ret, i, remoteNode);
	printf("%s",remoteNode);
	}
	printf("Hello");
	return ret;


}

[Rob Spoor]

Nandhini Venugopal wrote:

jclass cls = (*env)->FindClass(env,"/usr/jnieg/next");

First of all, the class literal should not have a leading /. Secondly, this value indicates the class name is usr.jnieg.next, but I don't see a package declaration. If the class is not in a package, just use "next". Otherwise use "usr/jnieg/next".

Also, I would never use AllocObject. It "Allocates a new Java object without invoking any of the constructors for the object." I doubt that's what you need. Even if no constructor does anything, I would still use one of the NewObject functions.


Oh, and the last printf doesn't do what you think it does. It does not call toString() on the object. It instead takes the pointer value and treats it as a pointer to a string (a char*). The result is garbage.

[Nandhini Venugopal]

Hi,
The problem is resolved after I changed Findclass as said.
Thanks for your help.

[Nandhini Venugopal]

Hi
Again i'm getting same error while trying out to get fieldid of an string array.
I modified the code as follows

FieldAccess.java

public class FieldAccess {

public static void main(String args[]) {

next[] Nxt;
next n=new next();
n.h=new String[100];
System.out.println(n.g);
Nxt=n.arrayFields();
for(int i=0;i<Nxt.length;i++){
System.out.println("In Java"+Nxt.length+Nxt[i].g);
}
}

 static {
	System.out.println("Hello");
   System.loadLibrary("FieldAccess");

 

  }

}

next.java

public class next{
public String g;
public String h[];

public static native next[] arrayFields();
static {
	System.out.println("Hello");
   System.loadLibrary("FieldAccess");

 

  }

}

FieldAccess.c

JNIEXPORT jobjectArray JNICALL Java_next_arrayFields
  (JNIEnv *env, jobject jobj){

	jobjectArray ret;
	int i,j;
	printf("Hello");
	jclass cls = (*env)->FindClass(env,"next");
	printf("Hello");
	ret= (jobjectArray)(*env)->NewObjectArray(env,10,cls,NULL);
	printf("Hello");
	if(ret==NULL){
	ret=NULL;
	}
	for(i=0;i<10;i++)
	{
	jobject remoteNode = (*env)->AllocObject(env,cls);
	if (remoteNode == NULL)
    	{
    		ret = NULL;
		}
	jfieldID fid,fid1;
	fid = (*env)->GetFieldID(env,cls, "g", "Ljava/lang/String;");
	fid1 = (*env)->GetFieldID(env,cls, "h", "Ljava/lang/String;");
	if (fid == NULL)
    	{
    		ret = NULL;
		}
	(*env)->SetObjectField(env,remoteNode, fid, (*env)->NewStringUTF(env,"Hello"));
	jstring str[2];
	for(j=0;j<2;j++)
	{
	char *k;
	k=malloc(strlen("Hello")+strlen("World")+1);
	strcpy(k,"Hello");
	strcat(k,"World");
	
        (*env)->SetObjectField(env,remoteNode, fid1, (*env)->NewStringUTF(env,k));
	
	}
	(*env)->SetObjectArrayElement(env,ret, i, remoteNode);
	(*env)->SetObjectArrayElement(env,ret, i, remoteNode);
	
	}
	printf("Hello");
	return ret;


}

[Rob Spoor]

Field h is not a String, it's a String[] (array of String). Your native code treats it as a String though.