Re: How to Retrieve Session User?
Re: How to Retrieve Session User?
- Subject: Re: How to Retrieve Session User?
- From: Jean-François Veillette <email@hidden>
- Date: Wed, 4 Apr 2007 23:47:49 -0400
Fred, consider that having an EO access a Session objet can be seen
as a bad practice (by me at least).
That being said, an EO frequently need to access the current logged
in user, either for validation or for business processing.
Then you realize that the concept of a current logged in user is part
of your business model, not just a display helper object.
My first implementation at solving this problem was to subclass
EOEditingContext and add a currentUser access method (and ivar to
support it). This allowed all my business layer to have access to
it, and worked like a charm.
I was fortunate enough that my business layer was all in a single
framework, so it was easy to get control over all the business
objects and they where all aware of the 'special' subclass given by
the context() method.
At the application level, when a user logged in, I had to set the
defaultEditingContext.currentUser. When I needed a different editing
context (peer or child), I had a methods that copied the additional
information from a given context (the defaultEditingContext). That
way it was relatively painless to keep the EO's context customized to
the context of my business logic.
You can see that this approach worked only because I had control over
all the business layer within a single framework. This approach
would be harder to implement in a context where you have business
objects from different frameworks that all need to access the
'current user' without sharing a common eoeditingcontext subclass
implementation. So either you get a generic editingContext subclass
across all your business frameworks, or you get into trouble and
prefer another approach.
My second implementation at solving this problem was to set the
delegate of the EOEditingContext, that way I thought that It would be
easier to integrate with other business logic frameworks since we all
use the bare-default implementation of eof. It worked, I set the
delegate to a 'consultation' object, which is more or less the
equivalent of a what a WOSession is to the interface layer.
But I'm still unconvinced, mainly because, one logic framework might
impose a different delegate that implement real
eoeditingcontext.delegate methods. Abusing the delegate
responsibilities will bites me on the long run, I have to find
another solution.
My next implementation at solving this problem will turn around a
common 'context' class that will have static methods to return the
current 'consultation' object given an EO (internally using the
eo.editingContext() has a key to map a consultation object). Draft
implementation :
public class Context {
HashMap contextHashMap;
public static Object context(Object ec) { return contextHashMap.get
(ec); }
public static void setContextForKey(Object ctx, Object key)
{ contextHashMap.put(key, ctx); }
}
Then somewhere early in Session constructor ... and/or anywhere I
create a new EOEditingContext I would do the same :
Context.setContextForKey(new
ConsultationObjectThatHoldMyBusinessLayerContextInformation(),
defaultEditingContext);
This is crappy code (we need a memory friendly implementation in
order to ease garbage collection of our context and key objects), but
you get the idea.
These are 2 working solutions (see my 2 first attempts at solving
this problem), so it is possible to solve it.
With so many brilliant WO developer around you will get a solution
that fits your mindset and your needs.
ps: KVC is the wrong tools for what you want to achieve.
- jfv
Le 07-04-04 à 21:09, Ken Anderson a écrit :
Fred,
I would verify that the session your setting the user on is the
same session your asking for the user. As Chuck mentioned earlier,
it's possible that you're creating sessions without realizing it.
Ken
On Apr 4, 2007, at 8:41 PM, Fred Shurtleff wrote:
It's a typo - really 2 lines.
// set the session.user ((Session) session()).takeValueForKey
(user, "user");
Chuck Hill wrote:
On Apr 4, 2007, at 5:34 PM, Fred Shurtleff wrote:
Gino, Mark, Chuck, Mike,
I have tried all of your 'best practice' suggestions (not
Chuck's yet), and STILL have no luck. To recap, this is my setup:
Session.java (declare a user)-
protected EOEnterpriseObject user;
Main.java (fetch/authenticate, & set the user in session)-
// fetch the user
EOEnterpriseObject user = EOUtilities.objectMatchingKeyAndValue
(session().defaultEditingContext(), "User", "name", username);
// set the session.user ((Session) session()).takeValueForKey
(user, "user");
Typo or is it really commented out?
Post.java (get the user for inserting transaction)=
EOEnterpriseObject user = (EOEnterpriseObject) ((Session) session
()).valueForKey("user");
At this point (using the debug mode) the user is null!! This
seems so... basic, yet I cannot see the problem. So if you see
something awry, please shout again.
It is sort of like a magic show. If I put something in a box,
and then later open the box and the thing is not in there, how
did this happen? Answer: it is not the same box. Try this:
// fetch the user
EOEnterpriseObject user = EOUtilities.objectMatchingKeyAndValue
(session().defaultEditingContext(), "User", "name", username);
// set the session.user
((Session) session()).takeValueForKey(user, "user");
NSLog.out.appendln("Registered user in session " + session
().sessionID());
Post.java (get the user for inserting transaction)=
EOEnterpriseObject user = (EOEnterpriseObject) ((Session) session
()).valueForKey("user");
NSLog.out.appendln("Retrieved user from session " + session
().sessionID());
Now, are the IDs the same or not? If not, check your HTML for
malformed HTML. On Mac? Use the iCab browser for its easy HTML
validation.
Chuck
Now what I think Chuck & Mike is saying is the above approach is
'taking a short cut' so-to-speak(using built-in KVC settor/
gettors), and is lacking for reasons mentioned. A better
practice is to code explicit java methods to message (get/set)
objects - a la OO Programming style.
I appreciate all your help & suggestions - Fred
Chuck Hill wrote:
Adding onto Mark's comments... KVC is for when you can't use
statically compiled Java. Using KVC instead of statically
compiled Java:
- reduces the chance of having the compiler catch your mistakes
- makes the code harder to read
- makes it harder to make naming changes
- makes you a bad person ;-)
In your session you should have:
private User loggedInUser;
public void setUser(User user) {
loggedInUser = user;
}
public User user() {
return loggedInUser;
}
And your code sample should read:
// set the session user
((Session)session()).setUser(user);
...
EOEnterpriseObject user = ((Session)session()).user();
And if it still evaluates to null, then your code is probably
creating more sessions than you realize.
Chuck
On Apr 4, 2007, at 3:58 PM, Mark Morris wrote:
Hi Fred,
KVC is certainly an integral part of WO, but much of that is a
bit behind the scenes. For instance, if you create the user()
and setUser() methods in your Session class, WO's KVC
implementation is what lets you bind session.user to a
WOString in a component. So you get the advantages, while
still getting the benefits of proper methods that Mike was
mentioning (such as some compiler error checking, easier
maintainability/internal documentation, and the ability to put
some logic in the accessor methods).
Regards,
Mark
On Apr 4, 2007, at 5:22 PM, Fred Shurtleff wrote:
Chuck,
I would welcome your comments on my KVC usage.
I was actually surprised by Mike's statement re: KVC
'funnybusiness' as I was led to believe from my readings that
KVC was a very integral part of WO. And the KVC concept seems
very straight-forward to me - what can be simpler than
takeValueForKey( value, key)? Also this is the technique I
have learned from a number of tutorials.
But then I am unable to put/get a user into the session - so
there must be something I am missing. Actually I have tried
so many ways to retrieve the user, I now think I never got
the user into the session to begin with. :-)
Chuck Hill wrote:
Listen to Mike. I was just about to write and make the same
complaint of your code. Abusing KVC is NOT your friend.
Chuck
On Apr 4, 2007, at 1:45 PM, Mike Schrag wrote:
PERSONALLY, I'd stop all this KVC funnybusiness. It has
its place and it's really powerful, but you're making your
life way obnoxious. Let Java do its job and just call
methods on things -- there are LOTS of benefits of this.
Define a proper user field on your Session class and do
setUser(..) and user() to retrieve it.
On Apr 4, 2007, at 4:40 PM, Fred Shurtleff wrote:
Mark - I understand where you are coming from, and did try
your suggestion. But I still am NOT getting a user EO
instance (I get null per the debugger).
Actually I checked the WO docs and both valueForKeyPath
AND valueForKey are valid methods of the Session class.
Problem is what is the correct syntax. The docs say
object.valueForKey(string), and your suggestion provided
the object part (ie session()) (I also tried your input +
valueForKeyPath but Eclipse complained about 'no such key
= session')
So I still am at a loss on how to retrieve a user EO from
the session. :-(
But thanks for your help/input!
Mark Morris wrote:
Hi Fred,
On Apr 4, 2007, at 3:10 PM, Fred Shurtleff wrote:
Hello,
I have a basic question on how to access the logged in
user for later use in updates. After authenticating a
user I enter him into the session, but when I later try
to retrieve this user in another page, it fails(returns
null).
So in my main page I record the user as follows:
if (_password.equals(password))
{ EOEnterpriseObject user =
EOUtilities.objectMatchingKeyAndValue(session
().defaultEditingContext(), "User", "name", username);
// set the
session.user session
().takeValueForKey(user, "user");
And on another page to add a new transaction which needs
the user relation attribute(as a foreign key):
EOEnterpriseObject user = (EOEnterpriseObject)
valueForKeyPath("session.user"); // user evals to null???
Try changing this to:
EOEnterpriseObject user = (EOEnterpriseObject)session
().valueForKey("user");
valueForKeyPath is useful, but I don't think it can do
what you're asking of it here.
purchase.addObjectToBothSidesOfRelationshipWithKey(user,
"user");
The save fails because user is a required attribute. And
I'm not sure if I am not properly storing the user in
the session, or not properly retrieving the user from
the session.
Can anyone see what I am doing wrong or suggest another
approach?
TIA
Personally, I usually make currentUser an actual variable
in Session. (Private, with public accessor methods, of
course! ;-)
Regards,
Mark
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