Custom serialization in blazeds

Question

Hi,
I'm using blazeds along with flex on the client side.
I have to deal with custom serialization (typically, sending a java.util.Currency object to the client).
I found out about the PropertyProxy/PropertyProxyRegistry, and managed to serialize thing the way I want.
I still have a few questions, though:
- The PropertyProxy interface defines a clone() method. When and why is this method called?
- What is this "default instance" concept in properties proxy?
- Can I fairly assume that the subclassed BeanProxy I wrote and instantiated will be shared among all threads?
Phrased differently: should implementations of PropertyProxy be written to be thread safe?
Everything suggests that they should, but I'd just like to be totally sure about this one.
I also have a question on serialization on the flex client side, but I'm not quite sure this is the correct forum to be asking it:
- Is there any PropertyProxy/PropertyProxyRegistry mechanism in flex in order to handle custom (de)serialization? We might not always be able/want to be using IExternalizable in flex.
Thanks

Answer 1

Hey Olivier,
These are great questions.
PropertyProxy's play two roles - the first is to control how EVERY instance of a complex type should be described for serialization, the second is to control how just this ONE instance of a complex type should be described for serialization.
The PropertyProxyRegistry simply maps a type (class or interface) to an instance of some PropertyProxy implementation. This serves as a reusable "template" that can be used for EVERY instance of a complex type as they pass through the serializer. (This avoids the wasteful creation of new PropertyProxy's just to introspect an instance of a complex type).
However, perhaps you have a special requirement for just ONE instance of your complex type. In this scenario you look up the appropriate PropertyProxy for the complex type - but you need to make some specific adjustment say, excluding some property but just this once, for your value. In this scenario the PropertyProxy acts as a wrapper and the value serves as the default instance of the PropertyProxy. The serializer will see the value is wrapped in a PropertyProxy and will not consult the PropertyProxyRegistry.
Now, the problem is that you don't want to modify the template PropertyProxy instance in the registry as that would impact EVERY other instance. So, you can clone the PropertyProxy for your ONE instance and make the adjustment.
If you didn't care about the state of the template PropertyProxy in the registry, you could also simply construct your own PropertyProxy instance and use that to wrap your value.
Since the template PropertyProxy instances are shared across threads, then they should not be modified in an unsafe manner. Generally, however, it's not a concern as template PropertyProxy instances are not modified after construction and the value to be introspected is passed in as an argument to the utility methods (rather than being part of the PropertyProxy state).
Pete