How not to send message?

[Ru.Lazukov]

Hello all =)

I use Tcp from receiving massages from device. Sometimes device open Tcp connect and close without any payload.

I use deserializer in tcp-connection-factory.
deserializer tryes to read anything from Stream, if there is something - it return founded thing...
But when nothing are come - i return null, and Spring Integrations throws exception "can not send message: null".

How can i correctly say to Spring that NO MESSAGE EXIST, so no processing shold be done.

[oleg.zhurakousky]

Could you post your configuration?
The message is correct, we don't allow messages with the 'null' payload, however, i am curious to see why it even attempts to create a Message with 'null' payload. We may need to improve there.

[Gary Russell]

Which deserializer are you using?

If it's a custom one, you need to throw a SoftEndOfStreamException to signal a 'clean' close.

For example, in the ByteArrayCrLfSerializer...

if (bite < 0 && n == 0) {
	throw new SoftEndOfStreamException("Stream closed between payloads");
}

If you are using one of our deserializers, please attach a debug log showing the error.

[Ru.Lazukov]

2 Oleg:

<int-ip:tcp-connection-factory
id="tcpInFactory-Device"
type="server"
port="***"
using-nio="false"
serializer="byteArrayLfConverter"
deserializer="byteArrayLfConverter"

pool-size="200"
so-keep-alive="false"
so-timeout="10000"
/>

<int-ip:tcp-inbound-channel-adapter
id="tcpInAdapter-Device"
channel="inChannel-Device"
connection-factory="tcpInFactory-Device"
/>

<int:channel id="inChannel-Device" />

byteArrayLfConverter is similar to ByteArrayCrLfSerializer written by Spring.

[Ru.Lazukov]

"The message is correct, we don't allow messages with the 'null' payload, however, i am curious to see why it even attempts to create a Message with 'null' payload. We may need to improve there"

TCP channel is opened, but NO payload are come. And channel are closed. Whay should i do in deserializer?

SoftEndOfStreamException -is not correct solution. It's an exception and it will be written to logs and admins will receive email that "SOMETHING BAD APPEARED - WE GOT EXCEPTION".

[Ru.Lazukov]

2 Gary:

Hi, how are you? I use your code with modifications:

public byte[] deserialize(InputStream inputStream) throws IOException {
        try {
            byte[] buffer = new byte[this.maxMessageSize];
            int n = 0;
            int bite;
            if (LOG.isDebugEnabled()) {
                LOG.debug("Some data arrived");
            }
            while (true) {
                try {
                    bite = inputStream.read();
                    if (bite < 0 && n == 0) {
                        throw new SoftEndOfStreamException("Stream closed between payloads");
                    }
                    checkClosure(bite);
                    //if message has non zero elements - end of message
                    if (n > 0 && bite == '\n') {
                        break;
                    }
                    //skipping \n data, because some devices send \n as TCP connection "heat beats"
                    if (bite != '\n') {
                        buffer[n++] = (byte) bite;
                        if (n >= this.maxMessageSize) {
                            throw new IOException("CRLF not found before max message length: "
                                    + this.maxMessageSize);
                        }
                    }
                } catch (SocketTimeoutException timeoutException) {
                    break;      //on timeout we trying to continue with all already read data
                }
            }
            //if n is ZERO - mean socket closed without any payload
            if (n == 0) {
                // HERE IS PROBLEM!!! What should i do to correctly say to Spring - no message exist, continue work without Exceptions
                throw new SoftEndOfStreamException("No data are readed from channel");
            }
            byte[] assembledData = new byte[n];
            System.arraycopy(buffer, 0, assembledData, 0, n);
            LOG.debug("some data readed, size {}", n);
            return assembledData;
        } catch (RuntimeException re) {
            LOG.error("error during data reading", re);
            throw re;
        } catch (IOException e) {
            LOG.error("IOException during data reading", e);
            throw e;
        }
    }

[Cleric]

Hello,
I think, SoftEndOfStreamException - is the best solution.
Your can define on your tcp-adapter an error-channel. And in the end you must write simple ErrorUnwrapper. That one checks Exception from message via instanceof SoftEndOfStreamException and doesn't send outbound message to reply-channel.

Is it suitable?

Artem

[Ru.Lazukov]

2 Cleric:

AFAIK Exception is UBNORMAL situation. And no data in socket is normal for my application.
Also AFAIK Exception handling is much more consuming than work without Exception

for example

        if(obj == null) {
            doSomeStuff();
        }

will be much faster than

        try {
            obj.getSomething()
        } catch (NullPointerException ex) {
            doSomeStuff();
        }

is not it?

And in my case possible that for one piece of cake i will receive ten empty connections.

[Cleric]

if(obj == null) {
doSomeStuff();
}

But it's not logic of deserializer...

[Ru.Lazukov]

I mean that no sense to use Exception in logically normal situation.

readData() {
...
            //if n is ZERO - mean socket closed without any payload
            if (n == 0) {
                // HERE IS PROBLEM!!! What should i do to correctly say to Spring - no message exist, continue work without Exceptions
                throw new SoftEndOfStreamException("No data are readed from channel");
            }
...
}

try { 
    readData();
} catch (SoftEndOfStreamException ex) { 
    //just skip message
}