JNI Error in passing array

[nandhu_venu]

I'm new to JNI programs. I'm doing one JNI code in which I need to pass array value from C to Java. While displaying in java the previous values are considered in array. As i'm new to JNI i couldn't solve this. This is the code:

FieldAccess.java

public class FieldAccess { 
  public static void main(String args[]) { 
    next[] Nxt; 
    next n=new next(); 
    n.h=new String[2]; 
    Nxt=n.arrayFields(); 
    for(int i=0;i<Nxt.length;i++) { 
      System.out.println("In Java i= "+i+" g Val= "+Nxt[i].g); 
      for(int j=0;j<2;j++) { 
        System.out.println("In Java i= "+i+" h Val= "+Nxt[i].h[j]); 
      } 
    } 
  } 
  static { 
    System.out.println("Hello"); 
    System.loadLibrary("FieldAccess"); 
  } 
}

next.java

public class next{ 
  public String g; 
  public String h[]; 
  public  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"); 
  ret= (jobjectArray)(*env)->NewObjectArray(env,50,cls,NULL); 
  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; 
    } 
    if (fid1 == NULL) { 
      ret = NULL; 
    } 
    jstring kk= (*env)->NewStringUTF(env,"Hi"); 
    (*env)->SetObjectField(env,remoteNode, fid,(jstring)kk);     
    jstring str[2]; 
    for(j=0;j<2;j++) { 
      str[0]=(*env)->NewStringUTF(env,"jj"); 
      str[1]=(*env)->NewStringUTF(env,"Hello"); 
    } 
    (*env)->SetObjectField(env,remoteNode, fid1, (jstring)str); 
    (*env)->SetObjectArrayElement(env,ret, i, remoteNode); 
  } 
  return ret; 
}

The output I'm getting is:

In Java i= 0 g Val= Hi 
In Java i= 0 h Val= Hi 
In Java i= 0 h Val= jj 
In Java i= 1 g Val= Hi 
In Java i= 1 h Val= Hi 
In Java i= 1 h Val= jj 
In Java i= 2 g Val= Hi 
In Java i= 2 h Val= Hi 
In Java i= 2 h Val= jj 
In Java i= 3 g Val= Hi 
In Java i= 3 h Val= Hi 
In Java i= 3 h Val= jj 
In Java i= 4 g Val= Hi 
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out                           
of range: -253510696 
at java.lang.String.getChars(String.java:724) 
at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:394) 
at java.lang.StringBuilder.append(StringBuilder.java:120) 
at FieldAccess.main(FieldAccess.java:94)

Please any one help

[keang]

It's a long time since I did any JNI so this advice may not be correct but it looks to me like you aren't setting the h array correctly. I think you need to assign a new object array of type string to h ie:

fid1 = (*env)->NewObjectArray(env, 2, env->FindClass("java/lang/String"), NULL);

and fill it from str ie

(*env)->SetObjectArrayRegion(env, fid1, 0, 2, str);

[nandhu_venu]

There is no functions in JNI like SetObjectArrayRegion. Give me any other option.

[keang]

Sorry, I did say it had been a long time since I did any of this.
I think the problem is with the line

 (*env)->SetObjectField(env,remoteNode, fid1, (jstring)str);

I'm just not sure what you need to do to sort it. Maybe try iterating over str and use SetObjectArrayElement to set each array element.