Problem while returning an object using JNI and accessing its fields and methods?

[manesh thomas]

I have to return an java object(IPDetails) from a java method using JNI.
I am using the following code for this.But the NULL value is getting.
Why this is becoming NULL.Is this the correct way of returning an Object
from a java function?
jobject ipDetails;
ipDetails = (*env)->CallObjectMethod(env,jobj,methodID,(*env)->NewStringUTF(env,userName));
The IPDetails class has 2 fields
a String field (ip) and a boolean field (accept)
.I want the 2 field values to be retrieved from the object
returned from the java method and be used in the C program.
For that,
jclass detailsClass = (*env)->FindClass(env,"com/test/IPDetails");
jfieldId ipID = (*env)->GetFieldID(env,detailsClass,"ip","Ljava/lang/String;");
jboolean acceptID = (*env)->GetFieldID(env,detailsClass,"accept","Z");
For getting the ip and accept fields of the ipDetails object which function
shall i use??
Can anyone suggest how can i call and get the above two fields
of the object returned.
Thanks

[Vijayakumar Arya]

Hi Manesh,
I did not get one thing, where are you instantiating the IPDetails object? Whether the instance of IPDetails is passed as a parameter in the native method.
I guess that you are trying to access the fields of the IPDetails instance,
For accessing the field of any instance you have to use

Get<type>Field Routines 
NativeType Get<type>Field(JNIEnv *env, jobject obj, 
jfieldID fieldID); 

Some examples:

Table 4-1 Get<type>Field Family of Accessor Routines  Get<type>Field Routine Name  Native Type  
GetObjectField()  jobject  
GetBooleanField()  jboolean  
GetByteField()  jbyte  
GetCharField()  jchar  
GetShortField()  jshort  
GetIntField()  jint  
GetLongField()  jlong  
GetFloatField()  jfloat  
GetDoubleField()  jdouble  

you have to pass the field id returned by the GetFieldId function. Also you can refer to the JNI documentation available within the Java API Documentation.
Hope this helps
[ February 21, 2003: Message edited by: Vijayakumar Arya ]