How to modify a parameter in C++ passed from java (structure Newbie)

Question

Hi,
I'm a brand new to Java (basically a C+ programmer). I have a C++ DLL that takes a structure as parameter from Java and I want to change (or populate) it in C++ DLL.
Here is what I'm trying...
// Java Code...
public class CSMSample
    public static class MyDetails
        String myName;
        long myAge;
        byte[] myBinaryData;
    public native static long SMGetMyDetails(MyDetails myDetails);
    public static void main(String[] args)
        MyDetails myDetails = new MyDetails();
        SMGetMyDetails(myDetails);
        System.out.println("My Name is " + myDetails.myName + " and I am " + myDetails.myAge + " years old");
    static
        try
            System.loadLibrary("SMSample"); //SMSample.DLL
        catch (Exception e)
            // Handle exception here ...
// C++ code
JNIEXPORT jlong JNICALL Java_CSMSample_SMGetMyDetails(
     JNIEnv* env, jclass, jobject jMyDetails)
    long error = 0;
    // I need to modify jMyDetails here and my Java program should be able to read the changes!
    return error;
}Can someone help me please!?
Thanks in advance,
John.

Answer 1

Hi
I'm doing the following:
// Java class...
public static class BYTE_ARRAY
     public long     Length;
     public byte[]     Data;
JNIEXPORT jlong JNICALL Java_CSMSample_SMGetCode(
     JNIEnv* env, jclass, jobject jByteArrayCode)
     BYTE_ARRAY Code;
     Code.Length = 8;
     Code.Data = new BYTE[Code.Length];
     Code.Data[0] = 'a'; Code.Data[1] = 'b'; Code.Data[2] = 'c'; Code.Data[3] = 'd';
     Code.Data[4] = 'e'; Code.Data[5] = 'f'; Code.Data[6] = 'g'; Code.Data[7] = '\0';
     jbyteArray code_data = env->NewByteArray (Code.Length);
     env->SetByteArrayRegion(code_data, 0, Code.Length, (const jbyte*) Code.Data);
     jclass cls = env->GetObjectClass(jByteArrayCode);
     jfieldID fid_Data = env->GetFieldID(cls, "Data", "[B");
     jfieldID fid_Length = env->GetFieldID(cls, "Length", "J");
     env->SetIntField(jByteArrayCode, fid_Length, Code.Length);
     env->SetObjectField(jByteArrayCode, fid_Data, code_data);
}Java application gets the Length properly but the data part is garbage (When I print, it gives [B@9304b1, same text even if I change the values of Code.Data). Am I missing something?
Thanks,
John.