Java as a Subscriber crash in receive data with IDL Nested #4660

hendraprawira · 2024-05-22T09:29:11Z

hendraprawira
May 22, 2024

i have an IDL like this :

module NTB2Data {
    
    struct DPTData {
        double depth;
        string source;
        unsigned short status;
    };

    @topic
    struct Message {
        unsigned long long time;
        DPTData DPT;
    };
};

but after i test with my publisher (java), it come crash in java, i didnt find the error line.
but after i check, the subscriber find the mh.value.DPT.status is null, i check again the publisher is already fill the value:

the Subscriber Class Listener is

public synchronized void on_data_available(DataReader reader) {
        MessageDataReader mdr = MessageDataReaderHelper.narrow(reader);
        if (mdr == null) {
            logging.error(String.valueOf(mdr),"on_data_available: narrow failed.");
            return;
        }

        MessageHolder mh = new MessageHolder(new Message());
        SampleInfoHolder sih = new SampleInfoHolder(new SampleInfo());
        sih.value.source_timestamp = new Time_t();
        NTB2StatusModel ntb2Data = new NTB2StatusModel();
        System.out.println(mh.value.time);
        while (true) {
            mdr.take_next_sample(mh, sih);
            int status = mdr.take_next_sample(mh, sih);
            if (status == RETCODE_OK.value) {
                if (sih.value.valid_data) {
                    System.out.println("LOL " mh.value.DPT);
                    ntb2Data.setAvailability(1);
                    try {
                        if(hasZeroValue(ntb2Data)){
                            //yellow
                            System.out.println("YELLOW ");
                            ntb2Data.setAvailability(3);
                        }else{
                            //green
                            System.out.println("GREEN ");
                            ntb2Data.setAvailability(1);
                        }
                    } catch (IllegalAccessException e) {
                        throw new RuntimeException(e);
                    }
                    ntb2Data.setCreatedTime(generateTimestamp());
                    SetResourceData.setResourceModel("ntb2", ntb2Data.getAvailability());
                    broadcastMessage("/ntb2-data", ntb2Data.toString());
                }
            } else if (status == RETCODE_NO_DATA.value) {
                return;
            } else {
                System.err.println("ERROR: take_next_sample_: "   status);
                return;
            }
        }
    }

anyone can help me? thanks
forgive me for bad english, thanks

Answered by mitza-oci

May 22, 2024

Some more specifics here:
struct Message in IDL turns in to public class Message in Java.
Message in IDL contains a member that's a DPT value. It's not a "pointer to" or a "reference to" a DPT value.
Java has no way to represent this data model, so it turns into a pointer which may be null. Since IDL doesn't have a concept of null here, values of Message which contain a null pointer may not be passed into IDL-generated code like this mdr.take_next_sample(mh, sih);

View full answer

mitza-oci · 2024-05-22T13:08:01Z

mitza-oci
May 22, 2024
Maintainer

OpenDDS/java/FAQ

Line 68 in 85561d5

- I'm seeing a null pointer exception or a JVM crash in an OpenDDS native

6 replies

mitza-oci May 22, 2024
Maintainer

Some more specifics here:
struct Message in IDL turns in to public class Message in Java.
Message in IDL contains a member that's a DPT value. It's not a "pointer to" or a "reference to" a DPT value.
Java has no way to represent this data model, so it turns into a pointer which may be null. Since IDL doesn't have a concept of null here, values of Message which contain a null pointer may not be passed into IDL-generated code like this mdr.take_next_sample(mh, sih);

Answer selected by hendraprawira

yuan-ge Jun 7, 2024

Dose this mean the custom data structure feature is not supported when used with Java?

mitza-oci Jun 7, 2024
Maintainer

It does not mean that.

yuan-ge Jun 8, 2024

So, what's the solution of the problem?🤔

hendraprawira Jun 8, 2024
Author

i'm already find the solution,
the solution is the struct of the message must be assign before calling take_next_sample(). like this:
` public synchronized void on_data_available(DataReader reader) {
MessageDataReader mdr = MessageDataReaderHelper.narrow(reader);
if (mdr == null) {
logging.error(String.valueOf(mdr),"on_data_available: narrow failed.");
return;
}
SampleInfoHolder sih = new SampleInfoHolder(new SampleInfo());
sih.value.source_timestamp = new Time_t();
NTB2StatusModel ntb2Data = new NTB2StatusModel();

    Message msg = new Message();

    msg.DPT = new DPTData();
    msg.HDT = new HDTData();
    msg.GLL = new GLLData();
    msg.MWV = new MWVData();
    msg.RMC = new RMCData();
    msg.VTG = new VTGData();
    msg.WIXDR = new WIXDRData();
    msg.ZDA = new ZDAData();
    msg.VHW = new VHWData();
    msg.PANZHRP = new PANZHRPData();
    MessageHolder mh = new MessageHolder(msg);

    while (true) {
        int status = mdr.take_next_sample(mh, sih);
        if (status == RETCODE_OK.value) {
            if (sih.value.valid_data) {
                System.out.println(mh.value);
            }
        } else if (status == RETCODE_NO_DATA.value) {
            return;
        } else {
            System.err.println("ERROR: take_next_sample_: "   status);
            return;
        }
    }
}`

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Java as a Subscriber crash in receive data with IDL Nested #4660

hendraprawira May 22, 2024

Replies: 1 comment · 6 replies

mitza-oci May 22, 2024 Maintainer

mitza-oci May 22, 2024 Maintainer

yuan-ge Jun 7, 2024

mitza-oci Jun 7, 2024 Maintainer

yuan-ge Jun 8, 2024

hendraprawira Jun 8, 2024 Author

hendraprawira
May 22, 2024

Replies: 1 comment 6 replies

mitza-oci
May 22, 2024
Maintainer

mitza-oci May 22, 2024
Maintainer

mitza-oci Jun 7, 2024
Maintainer

hendraprawira Jun 8, 2024
Author