| Description | The sender sends a message out of the application to the message system (like JMS, or an Enterprise Service Bus like Mule).
<p>
The underlying mechanism in GigaSpaces is a write to a space - this object is written as is to a space,
and it is picked up from there by the messaging system.
The advantage of using the space is that it is automatically backed up in a hot-backup deployment.
This means the message will be still be processed - possibly with a few seconds delay for the backup become primary,
but no other observable effect at the client.
</p><p>
There are normally multiple PUs in an application.
The object sent via the sender will be written to the PU containing the sender.
</p><p>
To be more exact in GigaSpaces, the sender is written into a space in the PU.
In general, GigaSpaces allows multiple spaces per PU - but in CloudTran v1, we only allow one space.
Therefore, you *can* specify a space on the sender model object.
In CloudTran v1, this will have no effect because the space is implied by the PU.
In future versions or different grid implementations of CloudTran, the 'space' property may mean something.
</p><p>
If the application that calls the sender does not specify a CloudTran transaction,
the output object is written immediately -
so it is possible for the ESB to action the output object immediately.
</p><p>
If the application specifies a non-null CloudTran transaction in the call to the sender,
then the output object is only written once the transaction successfully completes.
In other words, the send - and subsequent triggering of the ESB outbound endpoint - is part of the atomic transaction.
</p><p>
In theory, any object type can be sent to external systems.
However, note:
<ol>
<li>JavaBeans are marked as Serializable in the generated code, which may be acted on specially by the message transport.
</li>
</li>CloudTran generates classes specifically for representing in the in-memory data grid.
By default, these classes end in "Data".
You are asking for trouble if you send instances of these classes to external system.
</li>
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