Re: [Simple-support] stating the deserialization strategy on a class using annotation

[hatchetman82 <hat...@gm...>]

we have an enterprise system with a REST api. basically we're sending
and receiving XML over HTTP.
all of our methods send or receive Simple-xml-annotated classes that
represent either requests or responses. RESTeasy (the framework we use
to drive this API) provides a mechanism to derialize and deserialize
Objects into their string representation (XML in our case) via its
MessageBodyReader and MessageBodyWriter interfaces.
our use case revolves around the reader component. this is the
component that gets an input stream and a class type and is
responsible for deserializing an instance of this class type from the
input stream.

some of our simple-annotated classes require a strategy to deserialize
(this strategy needs to be provided as an argument to the Persister
constructor). since we know what type we intend to deserialize, we can
provide the appropriate strategy, but the resulting code is a giant
switchboard of if-elses and it not very pretty, fast or maintainable
as a result (this message body reader is a single point of entry to
the entire application).

since Persister receives the type to be serialized as the 1st argument
to its read() method, i was thinking it would have been nice to be
able to state the deserialization strategy on the simple-annotated
class somehow.

so, for instance, instead of doing this:

Strategy s = getStrategy(type); //ugly code hidden here
Persister p = new Persister(s);
Object result = s.read(type,inputStream);

i could have something like this on my class:

@DeserializationStrategy(MyStrategy.class)
@Root(name="myClass")
public class MyClass {
   //code here
}

and then i could create a Persister using the no-arg constructor, and
upon calling read() the persister could inspect the type (its getting
it as the 1st arg anyway) for @DeserializationStrategy, and if found
use that strategy to read the object from the input stream.
that would save us the need to find the strategy ourselves, and would
make the resulting code more elegant

On Mon, Feb 28, 2011 at 13:09, Niall Gallagher
<gal...@ya...> wrote:
> Hi,
>
> If you could provide more details that would be great! Not sure what your trying to achieve here. Have you tried the @Convert annotation or even a visitor?
>
> Niall
>
>
> --- On Sun, 27/2/11, hatchetman82 <hat...@gm...> wrote:
>
>> From: hatchetman82 <hat...@gm...>
>> Subject: [Simple-support] stating the deserialization strategy on a class using annotation
>> To: sim...@li...
>> Received: Sunday, 27 February, 2011, 10:47 PM
>> Hi.
>>
>> we use simple-xml to (de)serialize entity classes for out
>> application's REST api (using resteasy).
>> as part of the RESTeay api, there's an interface called
>> MessageBodyReader responsible for deserializing XML into a
>> java class
>> with the following signature:
>> public Object readFrom(Class type, /* stuff omitted */,
>> InputStream
>> inputStream);
>> deserializing some of our classes requires custom Strategy
>> implementations, which turns the implementation of the
>> above method
>> int a giant switchboard of if-elses according to the type
>> variable. it
>> would be very nice to be able to have some sort of
>> @DeserializationStrategy(value=[some strategy class])
>> annotation on
>> simple-xml-annotated classes to prevent this scenario.
>> is this possible?
>> if so, is it on the roadmap anywhere?
>>
>> thanks in advance for any assistance,
>>    radai.
>>
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