I'm sorry in advance if this rather n00bish question actually has an answer in the documentation which I've just failed to find, but
I'm still relatively new to GWT, and try as I might I can't find an explanation of what the request.with(String...) method actually does which I can understand. Please can someone explain to me in words of one sylable what this method does and why you'd use it?
thanks very much
It indeed is in the doc: https://developers.google.com/web-toolkit/doc/latest/DevGuideRequestFactory#relationships
By default, entity proxies referenced from the entity proxy/ies you're fetching are not fetched (properties will simply be null on the client-side). You have to explicitly ask for them using with(), passing the name (can be a dotted path too) of the properties you want to fetch.
Related
I've been reading the documentation of existingObject(with:), and it states:
If there is a managed object with the given ID already registered in the context, that object is returned directly; otherwise the corresponding object is faulted into the context.
I tried to find out what does register mean here however I couldn't anywhere for the last 1 hour. Then I tried to check if there's any method that let you register the object, which may shed light on the confusion, again I couldn't find any. Then I tried to print out all "register objects" with registeredObjects, the result is also a mystery.
Can anyone please explain or point me to the right source where I can understand what is this registering mechanism for managed object? And if possible maybe also point me to the right direction of understanding how exactly does core data, especially managed context work? (Everytime I thought I finally understood it, there seems to be more mystery)
I want ask if there is way to get an instance of a component if a job (ex:tmap, tmysqlinput) in tjava code and then manipulate it manually using code?
Thank you
Very hazardous. Looking at the generated Java code will give you some answers (I think so).
In fact, accessing to some objects properties is possible (there is blogs and articles about this) but changing anything seems to be dangerous (IMHO).
TRF
The details of the Request's with() implementation of RequestFactory in GWT is a bit unclear to me. See here for the official documentation.
Question 1:
When querying the server, RequestFactory does not automatically
populate relations in the object graph. To do this, use the with()
method on a request and specify the related property name as a String.
Does this mean that if the Entity at the server uses Lazy Fetching, the returned EntityProxy will have all the requested objects specified in with()? It seems a bit odd to instantiate the whole object graph of the Object server side, to only send a small piece to the client.
Question 2:
Does req.with("foo").with("foo"); do the same as req.with("foo"); ?
Question 3:
Does req.with("foo").with("bar"); do the same as req.with("foo","bar"); ?
NOTE: I'm having a really hard time finding the implementation details of with() in the source code and the API doesn't help me either.
Question 1:
It probably depends on your server side implemenation.
The with invocation will only make sure that the corresponding getter (getFoo()) is called shortly before the RF call returns to the client.
That's the reason why you also have to make sure to use an OpenSessionInView pattern, otherwise you might run into NullPointeterExceptions.
Question 2:
I guess the Request<T> implements a builder pattern.
The end-result will be the same.
However I am not sure if the getter() will be called twice or if the with method will check if the getter is already requested.
Question 3:
Yes it's the same.
As a sidenote. You can use req.with("foo.bar").
On the backend this will lead to a getFoo().getBar() call.
Sorry if this sounds stupid but I'm really new to LiftWeb and just struggling with the basic stuff:)
So I have a parametrized site map entry in Lift's bootstrap. This should be for the view page of an object of type MyItem. The URL would be like: "/myitems/UUID".
Menu.param [UUID]("MyItemView", "MyItemView", p=>Full(UUID.fromString(p)), p=>p.toString) / "myitems"
This adds the sitemap entry correctly. If I go to "/myitems/NOT_AN_UUID", it will throw the "Invalid UUID" exception as expected. But if I go to "/myitems/UUID" I get 404.
I know that I need a view and a snippet class that takes UUID as parameter in order for this to work but I have no idea how to name these and where to place them.
Btw, how would one new to Lift learn something like this? From the hundreds of articles and samples out there I found many to mention more complex stuff but haven't seen any to mention a basic thing like this. Do you know any secret start-up documentation for human beings?
Update: To summarize in case all you see above is jibber-jabber :) HOW DOES LIFT LOCATE TEMPLATES/VIEWS/SNIPPETS FOR PARAMETRIZED MENU ENTRIES?
It was actually the obvious answer. The template name is obtained from the path and the snippet can be whatever you want as long as you call it from the template xml.
I need to get used to all this convention over configuration :) However it would be nice for someone to tell you what is the convention.
I have a fairly simple question to which I cannot seem to find the answer for. I have a silverlight app with Ria Services. In the DomainService class I have an update method like below:
public void UpdateConversationState(ConversationState currentConversationState)
{
var original = ChangeSet.GetOriginal(currentConversationState);
if (original != null)
ObjectContext.ConversationStatesRepository.AttachAsModified(currentConversationState, original);
else
ObjectContext.ConversationStatesRepository.Attach(currentConversationState);
currentConversationState.UpdDat = DateTime.Now;
if(original.Name != currentConversationState.Name)
//Do something extra
}
The problem is that the Name property is always empty. In fact every field except for the Id has default values. I've tried searching for how the GetOriginal method works, but cannot find any help. It seems to mee like it tries to rebuild the original object on the server, based on the changes that are sent back from client to server.
Or maybe anyone knows a better way to check if a certain property of an object has been changed during an update? I could off course compare it to the value in the database, but it seems like I should avoid this extra call to the database.
Any help is again much appreciated :-)
EDIT:
Just found out about the RoundTripOriginalAttribute. This seems to do the trick. Am I the only one by the way that think RIA could be documented a little bit better?
Well, I've been also looking for a way track entity changes with EF4 and after some googling I've found that you need to apply the "RoundTripOriginal" attribute to the properties of the entity you want to track, because RIA (by default) does not send the original values back to the server.
I still have some concerns on this and I asked some of the gurus:
http://forums.silverlight.net/forums/t/218332.aspx
This worked for me, but I still don´t think is the best way out of it.
Hope this helps.