Glad to hear my ramblings were useful. :)
Also note that the "squeezers" are used (by default) in hidden form
components...
<input type="hidden" jwcid=..idden" value="ognl:myObject"/>
Using the custom squeeze adapter let's you do myObject and have your
form be happy,
instead of having to store the key and then implement a listener for the
hidden
field to restore the object manually.
Also, in tp4, the table, for, if and else components rely (by default;
this behavior can be changed) on squeezers to "do their thing" in
ensuring "safe" rewind, etc.
There may be others places, as well, but these are all the places I'm
aware of.
Robert
Gentry, Michael (Contractor) wrote:
>Robert,
>
>That's the clearest description of how/why to use a DataSqueezer I've
>seen so far. I don't currently use DirectLink for anything (I'm an
>ActionLink kind of guy), but if I ever do, I'll have to revisit this.
>
>Thanks!
>
>/dev/mrg
>
>
>-----Original Message-----
>From: Robert Zeigler [mailto:robert..uregumption.com]
>Sent: Tuesday, October 25, 2005 1:59 PM
>To: cayenne-use..bjectstyle.org
>Subject: Re: Tapestry integration
>
>
>Squeeze adapters just make life simpler when dealing with direct links,
>hidden form fields storing
>an object necessary for the form, etc.
>Consider, for example, the following:
>
><a href="#" jwcid=..irectLink" parameter="ognl:someDataObject">some
>link</a>,
>then w/out the squeeze adapter, you get the nasty serialized string
>storing the object, like:
>sp=zajwrk230jakzkeljk24j0jakljzlkjlkjlajk3wj0jzkjj2j1kjajajzkqweeraoiwr2
>412478997lksl2klaalkjoi4u389ull
>Or whatever. :) The url is ugly, but when you get your Object[] array
>in your listener, you have a nicely
>inflated object. Or... /mostly/ nicely. The issue here is that you
>wind up with a data object which isn't
>connected to any data context. So... ugly url /and/ problematic.
>
>To fix that, you could do (it's ugly all in ognl, but.... :)
><a href="#" jwcid=..irectLink"
>parameter="ognl..rg.objectstyle.cayenne.DataObjectUtils@intPKForObject(
>someDataObject">some
>link</a>
>Which gives you a "nice" url parameter like:
>sp=300
>
>Of course, then in your corresponding listener code, you're going to
>have to reverse that process... grab your object from your data context,
>based on the pk. So, clean url, no disconnected dataobject problems,
>but it's code that you essentially have to duplicate
>over and over again.
>
>Using the custom squeeze adapter, you would still do
>parameter="ognl:someDataObject".
>But then the generated url parameter would look something like:
>sp=Pnt/DataObject/300
>
>Still reasonably clean*, plus, you don't have to deal with the pk
>yourself, plus when you get your array of objects in your listener,
>you have a nicely "inflated" data object, /and/ it's connected to the
>data context**, to boot. :) You grab your object and go.
>
>It's certainly possible to /not/ use a squeeze adapter... tassel was
>written without one. But having now written it,
>I'd never go back to not using it. It's just one of those things which
>makes life that much nicer. :)
>
>Robert
>
>*caveat: if object.getObjEntity() returns null (which is the case if
>you used a newly created,
> unregistered data object, the object is squeezed
>according to the standard
> tapestry mechanism, so you still get something of an
>ugly url.
>
>**caveat: if the object was not registered with a data context when it
>was "squeezed", it won't be associated
> with a data context when unsqueezed. Eg: parameter="new
>org.me.SomeObject()"; said object
> wouldn't be associated with a datacontext on
>unsqueezing... and you wouldn't expect it to.
>
>
>
>Eric Schneider wrote:
>
>
>
>>Hi Robert,
>>
>>I probably haven't paid enough attention to the DataSqueezer posts on
>>the Cayenne/Tapestry mailing lists. I was under the assumption you
>>needed to implement a custom squeezer if you wanted bind a DataObject
>>as a DirectLink parameter. Are there other instances where the
>>standard Tapestry squeezing implementation with DataObjects jack me
>>
>>
>up?
>
>
>>I just haven't come across a problem (with a handful of apps), but
>>maybe I'm missing something?
>>
>>Thanks,
>>Eric
>>
>>On Oct 25, 2005, at 10:59 AM, Robert Zeigler wrote:
>>
>>
>>
>>>Sorry, I must've missed your e-mail on the tapestry list.
>>>Using the squeeze adapter is a matter of implementing the
>>>two interfaces it requires. One is ObjectIdStorageProvider.
>>>If you never use objects which are in state "NEW" in your pages,
>>>then this interface is unimportant and you can have a "dummy"
>>>implementation. Otherwise, what this interface is for is to
>>>store (in memory) the (temporary) ObjectId object or a data object in
>>>state NEW.
>>>
>>>The other interface is the "DataContextProvider" (single method:
>>>getValidDataContext()).
>>>The purpose is to provide the squeezer with a "valid" d.c. for the
>>>current
>>>thread.
>>>
>>>Once you've implemented the interfaces...
>>>
>>>If you're using tapestry 3.0.3, you'll have to subclass BaseEngine.
>>>In your subclass, override createSqueezeAdapter with something like:
>>>
>>> ISqueezeAdaptor[] adapters = {
>>> new DataObjectAdaptor(new DataContextProviderImp(),
>>>
>>>
>new
>
>
>>>ObjectIdStorageProviderImp())
>>> };
>>> return new DataSqueezer(getResourceResolver(), adapters);
>>>
>>>
>>>If you're using tapestry 4.0.beta-xxx, then you can skip the
>>>subclassing
>>>and just define the adapter in your hivemind config file.
>>>There are many examples of how to do this posted throughout
>>>the userlist archives, and I believe on the tapestry wiki, as well.
>>>
>>>Robert
>>>
>>>jaka lustek wrote:
>>>
>>>
>>>
>>>
>>>>Hi,
>>>>
>>>>I posted similar question on Tapestry list, but did not get the
>>>>
>>>>
>answer
>
>
>>>>so far. Can someone explain the steps to use CayenneDataSqueezer
>>>>
>>>>
>with
>
>
>>>>Tapestry. I downloaded the squeezer from Tassel. I don't want to go
>>>>statefull, is it possible to achieve this with CayenneSqueezer? I
>>>>hope I
>>>>am not asking silly questions.
>>>>
>>>>I have a tiny web app, just two pages, the first is collecting
>>>>
>>>>
>answers
>
>
>>>>with radio group buttons, and the second is collecting user data.
>>>>
>>>>
>The
>
>
>>>>model will use some three tables and some relationships. Simple
>>>>
>>>>
>model,
>
>
>>>>simple web app, but as I am new to Cayenne Tapestry world I need
>>>>
>>>>
>some
>
>
>>>>hints. I intend to present this app in my company as a proof of
>>>>concept
>>>>when will be ready (and this shold happen very soon).
>>>>
>>>>Thanks,
>>>>Borut
>>>>
>>>>____________________
>>>>http://www.email.si/
>>>>
>>>>
>>>>
>>>>
>>>>
>
>
>
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