Re: [jgroups-users] v3->v4 move, problem with castMessage

Hi Bobby,

On 26/10/17 20:13, Questions/problems related to using JGroups wrote:
> Hi again,
> 
> Am having various problems with our v3->v4 change. Trying to focus on 
> them one at a time, I wanted to ask about the castMessage change. We 
> were doing this before to send a message out to every node, collect 
> responses, etc:
> 
>          RspList<MyOb> rspList = md.castMessage(null,
>              new Message(null, myString), ro);
> 
> ...where myString is actually a constant starting with "n" and MyOb is a 
> Serializable object with some primitive data in it and one Address 
> object (*).

I don't see a myObj instance getting passed to the call?

> Now trying in v4.0.7 with this:
> 
>          RspList<MyOb> rspList = md.castMessage(null, 
> Util.stringToBytes(myString),
>              0, myString.length(), ro);


That won't work; myString.length() doesn't return the size of the 
generated byte[] array, better do this:

byte[] buf=Util.stringToBytes(myString);
RspList<MyOb> rspList = md.castMessage(null, buf, 0, buf.length, ro);



> ...but my Rsp (only 1 node so far) comes back with an exception instead 
> of MyOb:
> "java.lang.IllegalArgumentException: type 110 is invalid" (110 is the 
> first byte in the array).

Perhaps caused by the incorrect length argument above?

> I see that my handle() method is being called at the receiving end, and 
> the exception happens when I call Message#getObject() -- that code 
> hasn't changed from 3.x:
> 
>      @Override
>      public Object handle(Message msg) throws Exception {
>          final Object payload = msg.getObject();
>      }

You pass in a byte[] array generated by Util.stringToBytes(), so you 
*cannot* use Message.getObject() to retrieve it, but have to use the 
equivalent to de-serialize the byte[] array: Util.bytesToString().

> The getObject eventually calls Util#objectFromByteBuffer, and that 
> method is treating the first byte of the message as the type of the 
> message, and it falls apart there.

Right. So either use Util.objectToByteBuffer() and 
Util.objectFromByteBuffer() to marshall / unmarshall the payload, or 
stringToBytes() / bytesToString(), but don't mix and match!

> Is there some other way I should be handling this?
> 
> (*) Related: am getting a lot of FindBugs warnings now because we have a 
> couple Serializable objects we pass around that include Address objects, 
> and that isn't marked Externalizable any more. Any advice there would 
> also be appreciated.

I removed Serializable / Externalizable from Address, so they cannot be 
serialized with Java serialization (which is a bad idea anyway!). Use 
Util.writeAddress()/readAddress() instead

> Thanks,
> Bobby
> 
> 
> 
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> 
> 
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-- 
Bela Ban | http://www.jgroups.org


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