Re: Where to set display group bindings i java-file
Re: Where to set display group bindings i java-file
- Subject: Re: Where to set display group bindings i java-file
- From: Micky Holdorf <email@hidden>
- Date: Sat, 3 Dec 2005 13:03:08 +0100
Hi Jean-Francois,
The method invoked when clicking the link now looks like this:
public WOComponent visEmne() {
topic = subjectItem.subjectText();
quoteDisplayGroup.queryBindings().takeValueForKey("emne",
topic);
quoteDisplayGroup.qualifyDataSource();
return null;
}
and the WORepetition now looks like this:
Repetition1: WORepetition {
list = quoteDisplayGroup.allObjects;
item = quoteItem;
}
This makes more sense. ;)
Now it displays all entries from the Quote entity. Somehow it does
not use quoteDisplayGroup.queryBindings.emne and I have configured
quoteDisplayGroup to use emne as fetch spec. topic is set when the
user clicks a link. This works fine when defining fetch spec
programitically.
/Micky
On 02/12/2005, at 21.58, Jean-François Veillette wrote:
Hi Micky,
I am new to Webobjects and have no knowledge of Java. I learned C+
+ many years ago and have done some C and a lot PHP since then. So
then I could not get the DisplayGroup binding to work I became
frustrated and searched the internet for another solution and
found some code that worked. I am not realy used to object
oriented programming or thinking to this degree. I guess I do not
care about what knows what... or I am not aware of it anyway... ;)
Your example makes sense though.
Well then, welcome to WebObjects and this wonderful world !
I do beleive you're a brave soul to enter a new world you do not
have a mentor to guide you in, Bravo !
I'll try to explain apropriatly.
However, I used the DisplayGroup binding code that Wolfram
suggested like this:
public void appendToResponse(WOResponse aResponse, WOContext
aContext) {
topic = subjectItem.subjectText();
quoteDisplayGroup.queryBindings().takeValueForKey("emne",
topic);
quoteDisplayGroup.qualifyDataSource();
super.appendToResponse(aResponse, aContext);
}
this assume :
- you have a proper quoteDisplayGroup instanciated
- topic is not null
But it says null pointer exception in the appendToResponse
function when it display the webpage. What is the (WOResponse
aResponse, WOContext aContext) part of the function?
In WO, to generate a page, it goes like this (not exactly, but
close enough for now) :
- the application object receive the request (the url that point to
your app)
- somewhere it's dispatched to the right session object
- first, WO try to takeValuesFromRequest(...) if the request was a
form submit, this is when values are extracted.
- second, WO try to take action from that request : invokeAction
(...), the result of the action is going to be the answer returned
for the http request
- third, most of the time, invokeAction(...) return a WOComponent
as the result of an action, so we have to transform this
WOComponent into an http response (WOResponse), WO does it by
invoking appendToResponse(...) to fill the response object before
returning it's content.
So to answer your exact question, appendToResponse is invoked by WO
to ask your component to generate a response stream in WOResponse,
that will be ultimately returned to the requested client.
I then tried using it like this:
public WOComponent visEmne() {
topic = subjectItem.subjectText();
quoteDisplayGroup.queryBindings().takeValueForKey ("emne", topic);
quoteDisplayGroup.qualifyDataSource();
return null;
}
visEmne() will be called as part of 'invokeAction(...)' (see
above), returning null, mean to WO that it should ask the same
component used to generate the page the last action was somewhere
part of.
WO will find that page (context().page()) and ask it to
appendToResponse(...)
I have made a binding from quoteDisplayGroup.queryBinding.emne to
a WORepetion with two strings in it:
Repetition1: WORepetition {
list = quoteDisplayGroup.queryBindings.emne;
item = quoteItem;
}
String1: WOString {
value = quoteItem.author.firstName;
}
String2: WOString {
value = quoteItem.quoteText;
}
When a user clicks a link it uses the function visEmne() as an
action. But no entries from the Quote table show up.
Hmmm ... this is where it doesn't match up !
pretty sure quoteDisplayGroup.queryBindings.emne won't return an
NSArray
I'm not sure what you try to do, but try that instead :
list = quoteDisplayGroup.allObjects();
at least you might be closer to what you are looking for.
- jfv
/Micky
On 02/12/2005, at 19.15, Jean-François Veillette wrote:
Hi Micky,
1 ---
I don't mean to be picky, or to argue about the color of the
wallpaper, but I see something here that leave me perplex ...
The code seem to be in a WOComponent subclasss, and in this «
display » layer, you seem to know a lot about the « persistent »
layer.
Such code snippets is commonly found on the net as code sample,
and I give it myself as well, but once you get that code and
integrate it in your own code, you shouldn't leave it that way.
Such code should be divided into proper class, depending on
responsibilities, etc. The « display » layer
(com.webobjects.appserver.*) shouldn't know and deal too much
with the logic layer. Well, the problem is not much that it's
knowing something about the logic layer, it's more about it know
more about the logic internals than the logic layer itself !
For example,
// in « display / view » layer (WOComponent subclass) :
public WOComponent visEmne() {
emne = subjectItem.subjectText();
NSArray qts = Quote.quoteWithSubject(session
().defaultEditingContext(), subjectItem);
quoteDisplayGroup.setObjectArray(qts);
return null;
}
// in the Quote class, part of the « logic / model / business »
layer
public static NSArray quoteWithSubject(EOEditingContext ec,
Subject subj) {
NSArray args = new NSArray(new Object[] { subj });
String qualifierString = "(subject=%@)";
EOQualifier qualifier = EOQualifier.qualifierWithQualifierFormat
(qualifierString, args);
EOFetchSpecification fetchSpec = new EOFetchSpecification
("Quote", qualifier, null);
return ec.objectsWithFetchSpecification(fetchSpec);
}
This hide the internals of the relation between a quote and a
subject.
This will gradually beef up your « logic » layer to a point where
you could rewrite the same app, using a different gui framework
(think console based tools, web-service front-end or rich java-
client), and use a rich model to drive it.
As you can see, I've also changed the qualifier string, to test
against the subject object, not the subject string it contain.
This allow EOF to do a primary key join instead of a search on a
text column that you might not want to index.
2 ---
If you are building a search page with a form to qualify against
some attributes, you get values in instance variables, and then
user push 'search' to see the results.
For such situation, instead of binding the form element to
instance variable, you could bind it directly to the
displaygroup.queryMatch attributes.
For the above example, you could use a WOToOneRelationship
component to qualify on the quote.subject relationship. I do not
have sample code to give you, but I'm pretty sure there is a lot
somewhere on the web (or maybe right on your disk as part of the
wo example code).
3 ---
there is not point 3 ;-)
- jfv
Le 05-12-02, à 10:49, Micky Holdorf a écrit :
On 01/12/2005, at 18.15, Jean-François Veillette wrote:
I have a display group quoteDisplayGroup in a webcomponent.
The question is where in the components Java file I set the
binding:
quoteDisplayGroup.queryBindings().takeValueForKey(value,
"attributeValue");
and how...
Another question... in my research I have come upon this one:
quoteDisplayGroup.queryBindings().setObjectForKey(value,
"attributeValue");
Which one should I use?
think of queryBindings() as a NSMutableDictionary
( NSKeyValueCoding ), thus you can use both interfaces.
you can do it almost anywhere you want ( as far as it make
sense ;-) ).
- jfv
Hi there...
I never got it to work but I found another way to show the data
from the database. I use this code instead. It generates a
qualifier and fetch specification programmiticaly and populate
my displaygroup with the fetched data.
public WOComponent visEmne() {
emne = subjectItem.subjectText();
NSArray args = new NSArray(new Object[] { emne });
String qualifierString = "(subject.subjectText=%s)";
EOQualifier qualifier =
EOQualifier.qualifierWithQualifierFormat(qualifierString, args);
EOFetchSpecification fetchSpec = new EOFetchSpecification
("Quote", qualifier, null);
EOEditingContext ec = session().defaultEditingContext();
NSArray tempResultsArray = ec.objectsWithFetchSpecification
(fetchSpec);
quoteDisplayGroup.setObjectArray(tempResultsArray);
return null;
}
/Micky Holdorf
http://www.freeiPods.com/?r=21419063
http://www.freeiPods.com/?r=21419063
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden