what to store in session?
Consider following situation. User is logging into web application. What to store in session? 1. User object - it can be a large one (about 30 attributes, Strings, associated Objects). In this situation will be only one request to database (on user logon). Then all data will be taken from this object. 2. Put in session only user unique identifier (key) and then load neccessary data from database only when it's requested. Which one is better approach? md -- To unsubscribe, e-mail: mailto:[EMAIL PROTECTED] For additional commands, e-mail: mailto:[EMAIL PROTECTED]
RE: what to store in session?
I would say it depends. How expensive is a database hit and how many times do you find the need to hit the database to retrieve data? Is all the data used all the time or is just some of the data used? In your application is it acceptible to have a slight delay while loading the users profile? Is the users profile subject to change by other entities/system during their session? (can the data become stale?) These are some questions you need to ask yourself which will help determine your course of action. If it is acceptible to load all 30 attributes at logon AND the data does not have a chance of becoming stale AND you have the memory to accomodate it, then I would choose solution 1. Of course, if the user edits their profile, you will have to synchronize it with the database. If just some (a small portion) of the user's data is necessary, then I may choose a lazy loading scheme. robert -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Sent: Wednesday, June 26, 2002 9:20 AM To: [EMAIL PROTECTED] Subject: what to store in session? Consider following situation. User is logging into web application. What to store in session? 1. User object - it can be a large one (about 30 attributes, Strings, associated Objects). In this situation will be only one request to database (on user logon). Then all data will be taken from this object. 2. Put in session only user unique identifier (key) and then load neccessary data from database only when it's requested. Which one is better approach? md -- To unsubscribe, e-mail: mailto:[EMAIL PROTECTED] For additional commands, e-mail: mailto:[EMAIL PROTECTED] -- To unsubscribe, e-mail: mailto:[EMAIL PROTECTED] For additional commands, e-mail: mailto:[EMAIL PROTECTED]
RE: what to store in session?
Hi All, I'd add to Roberts very pertinent comments that Clustering as mentioned in an earlier post is also an issue here. If you intend to run your app in a cluster then session size becomes an issue; as your user object *may* be copied over the network to other machines. Also the projected number of concurrent users is an issue. Do you have enough memory (regardless of clustering issues) to hold all the user objects in memory? Jon Ridgway -Original Message- From: Robert Taylor [mailto:[EMAIL PROTECTED]] Sent: 26 June 2002 14:41 To: Struts Users Mailing List Subject: RE: what to store in session? I would say it depends. How expensive is a database hit and how many times do you find the need to hit the database to retrieve data? Is all the data used all the time or is just some of the data used? In your application is it acceptible to have a slight delay while loading the users profile? Is the users profile subject to change by other entities/system during their session? (can the data become stale?) These are some questions you need to ask yourself which will help determine your course of action. If it is acceptible to load all 30 attributes at logon AND the data does not have a chance of becoming stale AND you have the memory to accomodate it, then I would choose solution 1. Of course, if the user edits their profile, you will have to synchronize it with the database. If just some (a small portion) of the user's data is necessary, then I may choose a lazy loading scheme. robert -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Sent: Wednesday, June 26, 2002 9:20 AM To: [EMAIL PROTECTED] Subject: what to store in session? Consider following situation. User is logging into web application. What to store in session? 1. User object - it can be a large one (about 30 attributes, Strings, associated Objects). In this situation will be only one request to database (on user logon). Then all data will be taken from this object. 2. Put in session only user unique identifier (key) and then load neccessary data from database only when it's requested. Which one is better approach? md -- To unsubscribe, e-mail: mailto:[EMAIL PROTECTED] For additional commands, e-mail: mailto:[EMAIL PROTECTED] -- To unsubscribe, e-mail: mailto:[EMAIL PROTECTED] For additional commands, e-mail: mailto:[EMAIL PROTECTED] The contents of this email are intended only for the named addressees and may contain confidential and/or privileged material. If received in error please contact UPCO on +44 (0) 113 201 0600 and then delete the entire e-mail from your system. Unauthorised review, distribution, disclosure or other use of this information could constitute a breach of confidence. Your co-operation in this matter is greatly appreciated. -- To unsubscribe, e-mail: mailto:[EMAIL PROTECTED] For additional commands, e-mail: mailto:[EMAIL PROTECTED]
Re[2]: what to store in session?
On Wednesday, June 26, 2002, 12:31:11 PM, Craig wrote: CRM * Do not store complete data structures that are large and complex, CRM unless they really represent shared application data (in which case CRM they should probably be in the servlet context attributes instead). CRM * Hide the caching choice you are making inside the get methods of your CRM user object, so you can change your mind later without modifying all CRM the code that uses the data. I know this is probably a pretty newbie question, but... How is it different storing something in the servlet context vs having a static member in a class that is only loaded once when null? In other words I'm tending to use your second approach above, where say I need a list of StoreBeans I call a getStores() from a Commons class that first checks if the StoresList is null, and if it is null it loads them up. Am I correct in assuming that subsequent requests by ANY other session to the getStores() method will not load them up once any session has called the method? If that assumption is correct, is the only difference then in storing a List in the servlet context a matter of being able to use the List on any JSP page without having to set it there first in some action class (as you would have to do with a List you got from a getStores() method in some class)? Thanks for the help Rick -- To unsubscribe, e-mail: mailto:[EMAIL PROTECTED] For additional commands, e-mail: mailto:[EMAIL PROTECTED]
Re[2]: what to store in session?
On Wed, 26 Jun 2002, Rick Reumann wrote:
Date: Wed, 26 Jun 2002 14:19:52 -0400
From: Rick Reumann [EMAIL PROTECTED]
To: Craig R. McClanahan [EMAIL PROTECTED]
Cc: Struts Users Mailing List [EMAIL PROTECTED]
Subject: Re[2]: what to store in session?
On Wednesday, June 26, 2002, 12:31:11 PM, Craig wrote:
CRM * Do not store complete data structures that are large and complex,
CRM unless they really represent shared application data (in which case
CRM they should probably be in the servlet context attributes instead).
CRM * Hide the caching choice you are making inside the get methods of your
CRM user object, so you can change your mind later without modifying all
CRM the code that uses the data.
I know this is probably a pretty newbie question, but...
How is it different storing something in the servlet context vs
having a static member in a class that is only loaded once
when null?
If the class defining this static variable is loaded from the webapp class
loader (/WEB-INF/classes or /WEB-INF/lib), there is not a lot of
difference (although in Servlet 2.3 you have the option to use context
attribute listeners to detect when attributes are added, removed, or
replaced).
If the class defining this static is loaded from a shared library
directory (i.e. something like common/lib in Tomcat), then there is only
one copy of the static variable for *all* webapps.
Context attributes are always global to the entire webapp, but never
shared across webapps, no matter how you organize your classes themselves.
In other words I'm tending to use your second
approach above, where say I need a list of StoreBeans I call a
getStores() from a Commons class that first checks if the
StoresList is null, and if it is null it loads them up.
That's a good plan.
My suggestion is to implement this logic inside a bean that hides whether
or not you are really caching the data or not -- say a StoresBean
something like this:
public class StoresBean {
public ArrayList stores = null;
public synchronized Iterator getStores() {
if (stores == null) {
stores = new ArrayList();
... fill in the objects in this list ...
}
return (stores.iterator());
}
}
That way, the relevant stuff will get loaded the first time and then
reused. But your calling application doesn't know that -- all it needs to
do is grab StoresBean out of the session attributes (if this is user
specific) or context attributes (if this is global), and call getStores().
Am I correct in assuming that subsequent requests by ANY other
session to the getStores() method will not load them up once
any session has called the method? If that assumption is
correct, is the only difference then in storing a List in the
servlet context a matter of being able to use the List on any
JSP page without having to set it there first in some action
class (as you would have to do with a List you got from a
getStores() method in some class)?
If the StoresBean bean is in session scope, then getStores() will go load
up the list once per user. That makes sense, for example, if the list of
stores accessible to each user is different. You would want to create
this bean, and store it as a session attribute, as part of your logon
processing -- or make it a property of the user bean if you are already
storing that in session scope.
If the StoresBean bean is in application scope (i.e. a servlet context
attribute), then getStores() will go load up the list the first time *any*
user requests it, then everyone will share. This makes sense if the data
is global to all users. You would want to create this bean as part of
your application startup, by either:
* In servlet 2.3, create a ServletContextListener and set it up
in the contextCreated() method.
* In servlet 2.2 or later, create a servlet that is configured for
load-on-startup, and set it up in the init() method.
* In servlet 2.2 or later, subclass the ActionServlet class in Struts,
and override the init() method like this:
public void init() throws ServletException {
super.init();
... initialize context attributes here ...
}
and use this as the controller servlet.
Thanks for the help
Rick
Craig
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Re[3]: what to store in session?
Thanks so much Craig, this has been tremendously helpful! Some
comments below...
On Wednesday, June 26, 2002, 2:38:54 PM, Craig wrote:
CRM My suggestion is to implement this logic inside a bean that hides whether
CRM or not you are really caching the data or not -- say a StoresBean
CRM something like this:
CRM public class StoresBean {
CRM public ArrayList stores = null;
CRM public synchronized Iterator getStores() {
CRM if (stores == null) {
CRM stores = new ArrayList();
CRM ... fill in the objects in this list ...
CRM }
CRM return (stores.iterator());
CRM }
CRM }
CRM That way, the relevant stuff will get loaded the first time and then
CRM reused.
Ok, you've started to clear some things up for me. I always
thought thought that classes in my: myAppDir/WEB-INF/classes
directory if they had static members they were shared across the
entire application scope? This definitely is wrong though? (and
it's only session scope?).
In your above code, though, each user session would then end up
loading a new list of stores. I don't really need that. I only
need that list being loaded once and shared amongst all the
sessions.
CRM But your calling application doesn't know that -- all it needs to
CRM do is grab StoresBean out of the session attributes (if this is user
CRM specific) or context attributes (if this is global), and call getStores().
How would I grab this global attribute from a business layer
object though? I guess that's where I'm getting confused. Say I
have my Action class call a business object:
BO.getStoresList()
Well now I want the BO to return me a List of StoreBeans, but I
only want that list populated ONE time and want all the sessions
to share it.It looks like if I want all the sessions to share the information
I have to pass servlet classes into my model layer? Am I wrong
there?
CRM If the StoresBean bean is in application scope (i.e. a servlet context
CRM attribute), then getStores() will go load up the list the first time *any*
CRM user requests it, then everyone will share. This makes sense if the data
CRM is global to all users. You would want to create this bean as part of
CRM your application startup, by either:
CRM * In servlet 2.2 or later, create a servlet that is configured for
CRM load-on-startup, and set it up in the init() method.
Ok, I have set up some like this in the init() method of an
IntializationServlet I call on startup:
context.setAttribute( storeList, storeList );
CRM * In servlet 2.2 or later, subclass the ActionServlet class in Struts,
CRM and override the init() method like this:
CRM public void init() throws ServletException {
CRM super.init();
CRM ... initialize context attributes here ...
CRM }
OK! Perfect this is exactly what I should do. Thank you.
(I take it there weren't be any issues doing this to my
controller which extends DispatchAction).
Thanks Craig,
Rick
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Re[3]: what to store in session?
On Wed, 26 Jun 2002, Rick Reumann wrote:
Date: Wed, 26 Jun 2002 15:16:11 -0400
From: Rick Reumann [EMAIL PROTECTED]
To: Craig R. McClanahan [EMAIL PROTECTED]
Cc: Struts Users Mailing List [EMAIL PROTECTED]
Subject: Re[3]: what to store in session?
Thanks so much Craig, this has been tremendously helpful! Some
comments below...
On Wednesday, June 26, 2002, 2:38:54 PM, Craig wrote:
CRM My suggestion is to implement this logic inside a bean that hides whether
CRM or not you are really caching the data or not -- say a StoresBean
CRM something like this:
CRM public class StoresBean {
CRM public ArrayList stores = null;
CRM public synchronized Iterator getStores() {
CRM if (stores == null) {
CRM stores = new ArrayList();
CRM ... fill in the objects in this list ...
CRM }
CRM return (stores.iterator());
CRM }
CRM }
CRM That way, the relevant stuff will get loaded the first time and then
CRM reused.
Ok, you've started to clear some things up for me. I always
thought thought that classes in my: myAppDir/WEB-INF/classes
directory if they had static members they were shared across the
entire application scope? This definitely is wrong though? (and
it's only session scope?).
No, you've got that right. It's just that classes loaded from something
like the common/lib dirctory in Tomcat are shared across *all* web
applications, not just yours.
In your above code, though, each user session would then end up
loading a new list of stores. I don't really need that. I only
need that list being loaded once and shared amongst all the
sessions.
Some people do need per-user-specific stuff for some things. The same
design pattern works for both scenarios -- it's just a matter of where you
store the bean (and how it builds the list of available stuff).
CRM But your calling application doesn't know that -- all it needs to
CRM do is grab StoresBean out of the session attributes (if this is user
CRM specific) or context attributes (if this is global), and call getStores().
How would I grab this global attribute from a business layer
object though? I guess that's where I'm getting confused. Say I
have my Action class call a business object:
BO.getStoresList()
Well now I want the BO to return me a List of StoreBeans, but I
only want that list populated ONE time and want all the sessions
to share it.It looks like if I want all the sessions to share the information
I have to pass servlet classes into my model layer? Am I wrong
there?
As a servlet context attribute, the simplest way would be to have your
Action grab it (getServle().getServletContext().getAttribute()) and pass
it to the business object. But we're getting into territory where there
are a number of different approaches -- I would suggest consulting some of
the good design pattern books like the J2EE Blueprints series from Sun, my
favorite design patterns book Core J2EE Patterns by Alur, Crupi, and
Malks, and others. The issues of how business objects get access to data
(or JDBC connections, or ...) are universal, not limited to Struts apps or
even web apps.
CRM If the StoresBean bean is in application scope (i.e. a servlet context
CRM attribute), then getStores() will go load up the list the first time *any*
CRM user requests it, then everyone will share. This makes sense if the data
CRM is global to all users. You would want to create this bean as part of
CRM your application startup, by either:
CRM * In servlet 2.2 or later, create a servlet that is configured for
CRM load-on-startup, and set it up in the init() method.
Ok, I have set up some like this in the init() method of an
IntializationServlet I call on startup:
context.setAttribute( storeList, storeList );
CRM * In servlet 2.2 or later, subclass the ActionServlet class in Struts,
CRM and override the init() method like this:
CRM public void init() throws ServletException {
CRM super.init();
CRM ... initialize context attributes here ...
CRM }
OK! Perfect this is exactly what I should do. Thank you.
(I take it there weren't be any issues doing this to my
controller which extends DispatchAction).
Well, you can certainly do it there ... but it feels sort of hidden away
to me. You also have to be aware of thread safety for this, where the
init() method (or servlet context listener) is guaranteed to complete
before any request can be processed.
Thanks Craig,
Rick
Craig
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Re[4]: what to store in session?
Sorry Craig, I just realized I misread some of what you originally
wrote. You were talking about sharing 'across' applications and I
wasn't concerned with that so much. You can ignore my previous post. I
apologize.
Rick
On Wednesday, June 26, 2002, 3:16:11 PM, Rick wrote:
RR Thanks so much Craig, this has been tremendously helpful! Some
RR comments below...
RR On Wednesday, June 26, 2002, 2:38:54 PM, Craig wrote:
CRM My suggestion is to implement this logic inside a bean that hides whether
CRM or not you are really caching the data or not -- say a StoresBean
CRM something like this:
CRM public class StoresBean {
CRM public ArrayList stores = null;
CRM public synchronized Iterator getStores() {
CRM if (stores == null) {
CRM stores = new ArrayList();
CRM ... fill in the objects in this list ...
CRM }
CRM return (stores.iterator());
CRM }
CRM }
CRM That way, the relevant stuff will get loaded the first time and then
CRM reused.
RR Ok, you've started to clear some things up for me. I always
RR thought thought that classes in my: myAppDir/WEB-INF/classes
RR directory if they had static members they were shared across the
RR entire application scope? This definitely is wrong though? (and
RR it's only session scope?).
RR In your above code, though, each user session would then end up
RR loading a new list of stores. I don't really need that. I only
RR need that list being loaded once and shared amongst all the
RR sessions.
CRM But your calling application doesn't know that -- all it needs to
CRM do is grab StoresBean out of the session attributes (if this is user
CRM specific) or context attributes (if this is global), and call getStores().
RR How would I grab this global attribute from a business layer
RR object though? I guess that's where I'm getting confused. Say I
RR have my Action class call a business object:
RR BO.getStoresList()
RR Well now I want the BO to return me a List of StoreBeans, but I
RR only want that list populated ONE time and want all the sessions
RR to share it.It looks like if I want all the sessions to share the information
RR I have to pass servlet classes into my model layer? Am I wrong
RR there?
CRM If the StoresBean bean is in application scope (i.e. a servlet context
CRM attribute), then getStores() will go load up the list the first time *any*
CRM user requests it, then everyone will share. This makes sense if the data
CRM is global to all users. You would want to create this bean as part of
CRM your application startup, by either:
CRM * In servlet 2.2 or later, create a servlet that is configured for
CRM load-on-startup, and set it up in the init() method.
RROk, I have set up some like this in the init() method of an
RRIntializationServlet I call on startup:
RRcontext.setAttribute( storeList, storeList );
CRM * In servlet 2.2 or later, subclass the ActionServlet class in Struts,
CRM and override the init() method like this:
CRM public void init() throws ServletException {
CRM super.init();
CRM ... initialize context attributes here ...
CRM }
RR OK! Perfect this is exactly what I should do. Thank you.
RR (I take it there weren't be any issues doing this to my
RR controller which extends DispatchAction).
RR Thanks Craig,
RR Rick
RR --
RR To unsubscribe, e-mail: mailto:[EMAIL PROTECTED]
RR For additional commands, e-mail: mailto:[EMAIL PROTECTED]
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mailto:[EMAIL PROTECTED]
Sometimes you have to be careful when selecting a new name for
yourself. For instance, let's say you have chosen the nickname 'Fly
Head. Normally you would think that 'fly Head' would mean a person who
has beautiful swept-back features, as if flying through the air. But
think again. Couldn't it also mean 'having a head like a fly'? I'm
afraid some people might actually think that.
-Jack Handey
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