I am working with ASP.NET MVC 3.0. I have a page with an action link that makes appear a window in which you can adjust a certain value. Once the new value is sent to the database, an extern application deals with the value and send the result back to that database. I want the action link to be disabled while the extern application is doing her job. The page I am working on is refreshing automatically with some AJAX calls. The date when the extern application finished her last adjustment on a value is kept in the database. I first thought I could use session variables to store the date time of when the action link was pressed (because I need it through all the application) and then enable the action link when the adjust time is greater than the time when the action link was pressed, but I heard it was bad practices. Does someone have another solution?
Since you are already using the database - query the database to check the current status. If your application is restarted - a session value would be lost unless you are using a state server (ie sql server) to manage state- unless you don't care if its lost upon restart. You can use session and save yourself database calls - but the database is a bit cleaner and doesn't suffer from the same issue. If you do end up using the session, don't spread that session value all over your code, simply have a single method that reads or sets it (same with the db solution as well)
Related
I have a variable, session.acclevel, which is set during the login process (the program is login2.cfm).
<cfset session.acclevel = logdata['LOGACCESS'][1]>
The values can be N,R,W,A,M, and they are retrieved with query name = "logdata" from a table which I'm calling XXX here. If the login is successful, login2.cfm redirects to program navbar.cfm
<cflocation url = "navbar.cfm?welc=yes">
which is a set of dropdown menus, rather like a dashboard. Depending on the value of session.acclevel navbar shows more or fewer options. The session.acclevel variable is also used throughout the system to control various user activities.
All this was working fine, and then it suddenly stopped working -- session.acclevel was fine when navbar started up, but disappeared as soon as any selection was made. Yet, no code had been changed. The only thing I had changed was to alter the MySql table definition of the acclevel` variable type:
alter table XXX change LogAccess LogAccess enum('A','W','R','N','M');
to add the option 'M' to the enum. I did not chnage any data in that table, and I made no changes to the coding anywhere.
I double checked the timeouts (I am using system admin defaults), and tried without success to trace where the variable was getting lost. I closed and reopened the browser, without fixing anything.
Finally I went to the administrator and changed session management to J2EE -- and that fixed it. session.acclevel is now staying put.
Could someone explain what was going wrong there? I would like to know in case this defect in the ColdFusion session management is caused by weak code that I could avoid, or in case it later breaks under J2EE management.
After a research it seems that Meteor Sessions are reset after refreshing page or opening the website in new tab, i.e. they are not usual server-side sessions but something like global javascript variables on client-side. Some people advice to use AmplifyJS, but I'm not sure that it will work like usual session in other frameworks/languages and also it is a third party library, so is there any normal way to use sessions in Meteor, i.e. keep user-specific data on server?
At this moment I'm handling that by using custom Collections, but it is not an ideal way of doing that because it is needed to remove expired values from Collection manually, which makes additional troubles.
Yes this is correct. Despite the name Session is nothing like a cookie, but just a reactive form of a variable stored in a hashmap
To keep data persistent across tabs you need to use a Collections (as this is the only way to reactively share data across tabs) - Cookies can't work because they can't be made reactive as data needs to be sent to the server to notify the client when there is a change. There really wouldn't be another way at the moment as the publish/subscribe methods can only send down data from collections at the moment.
You can use your setup you have now with your custom collection. You can use a server side cron job to remove expired data (either with Meteor.setInterval or Tom Coleman's cron.
There is a package developed just for that: https://atmospherejs.com/u2622/persistent-session
After installation you can use the following functions to set sessions which are persistent:
//store a persistent session variable which is stored across templates
Session.setPersistent(key, value);
//same as above, but automatically deletes session data when user logs out
Session.setAuth(key, value);
I've tried the package and it works like charm.
I've an MVC3 web app which uses the default "in process" session. I've the PRG pattern in place - that is while postback if my modelstate is invalid I store the model in TempData and redirect to the original get action. In the get action I fetch the model data (if it exists) and send to the view. I believe this is one of the basic aspects of MVC.
I've learned that TempData in background is a session variable which
is used in the PRG transition. What I need to know is whether it is
possible to have a conflict or cross refrencing - if I use something
like TempData["model"] in two pages and access the pages
simultaneously. Would that overwrite the common data in
TempData["model"] or is it safe if I use the same tempdata names in
two different pages.
And does it conflict with Session["model"] kind of data? I'm facing some unexpected session data corruption - possibly due to my internal code that resets the session data or something else. Is it possible that session data can corrupt partially? I mean Session["data1"] is ok but Session["data2"] is gone?
My users often use the web app for a long duration causing session timeout. I tried for the ASP.Net session state service for session but that caused performance issues because I store some heavy objects (via serialization) in session. So finally I was back to the original default in proces mode.
Pls share if you've had any similar experiences.
TempData by default uses SessionState and access to SessionState is by default exclusive. So, if you do two concurrent reuquests, one will have to wait for the other to release the SessionState lock.
TempData does not interfere with using SessionState directly.
As SessionState by default uses in-proc, it can be invalidated almost anytime.
You might want to have a look at http://brockallen.com/2012/06/11/cookie-based-tempdata-provider/
Im pretty new to struts2 and Ajax ,Actually i have a drop down menu in JSP lets say first.jsp, When user select a choice from dropdown menu,I am calling a function of Action class lets say Method1.In this method i am fetching some value from DB(lets say:a,b,c) and one value from java memory lets say d.Then I am forwarding to second.jsp and display all the parameters(a,b,c and d) in tabular format.
Now problem is that the parameter d is dynamic ,this is updating by some other application and if its change then I have to show it on JSP wihout any action.
One solution is I use in second.jsp , so after interval of 10 second again Mehod1 will call and it will fetch value(a,b,c) from db and updated value of d from java memory. and disply it to second.jsp.But in this case i am unnecessary retrieving value from db while my purpose is just to get value d from memory.This is working but this is causing my application to slower.
Can any body suggetst some other solution? or can i do it using ajax and how?
Any other advice? any help is appreciated.try to be more clear, i'm in lack of ideas in this problem, even it sounds like a classic :I have spend hours trying to play around with this but have got nowhere
Okay... What you're asking is a little fuzzy so let me rephrase:
You have a user (USER1) who opens a web page and sees some data.
You have a second user (USER2) (who may be an application) who is able set a value from time to time.
When USER2 updates that value you want USER1 to see it change in their open browser window?
If this is the case you need to understand basic ajax. For that get these demo applications working:
This example uses dojo and perhaps the S2 ajax tag lib I don't remember I prefer not to use ajax tags (as they are deprecated and prefer jquery for ajax):
http://struts.apache.org/2.x/docs/struts-2-spring-2-jpa-ajax.html
This example here shows a very similar application but using jquery, no tag library, upgraded to Spring 3, it still needs polish:
http://www.kenmcwilliams.com/Downloads/
Now that you know how to get data via ajax, look at the request with firebug. You'll see that the request is just like a typical function call, the browser keeps waiting for the data to come back.
What you do is simply not return from the action until new data is provided. This is called long polling see: http://en.wikipedia.org/wiki/Comet_%28programming%29#Ajax_with_long_polling
If you have not written a simple chat program, using just terminal windows I recommend you do so. Two windows per client (client-send, client-receive windows) and you'll need a server program. I remember hacking one together in a few hours using _Thinking In Java 2nd Edition (Later books took out the networking section if I remember correctly). Anyways between understanding client server interaction and long polling will let you get things working. It would be fun to extend the simple terminal based chat application to a S2 ajax chat application. Would make an awesome tutorial! PS: This is just an application of the producer/consumer problem (If you understand that then I guess you don't need to do the fun exercise).
The interfaces would look very pretty if the server was managed by spring. I know there must be nice servers already written but I am not familiar with any, but would love to hear of one.
I'm looking at using Subsonic with a multi-tenant ASP.net web application. There are multiple DB's (one per client/instance). The user logs in with a domain suffix to their username (e.g. user#tenant1, user#tenant2).
The custom membership provider will then determine which database a user is using, and authenticate against it. All user-initiated calls in the webapp will be wrapped in a SharedDbConnectionScope call, however I have a question regarding caching subsonic items.
Basically each instance will have a few records that rarely change (search options/configurations). I would like to read these in the Application_Start event, and cache them into the ApplicationState.
In the Application_Start event, it would loop over each client database, use a SharedDbConnectionScope to connect to each DB, and create these cached records (e.g. Application('tenant1_search_obj') = subsonic_object
When a user loads the search page, it would then check what domain a user is in, and then retreive that search option from the cache.
Is this feasible? I'm just concerned that if I cache an object, when I retrieve it from the application cache it won't know what connection its using, and might possibly pull in the wrong data.
I'd like to avoid putting this in the session object if possible.
it's possible, but probably not a good idea since it doesn't scale at all - you're going to pop a new connection for every single client whether they show up or not.
Maybe your best bet is to "lazy load" the setting - first hit on the search page loads the config into the cache or Application settings and there it stays.
Other than that - to answer your question it is possible. If you're using SubSonic 3, just create a new provider on the fly using ProviderFactory.GetProvider(connectionString, "System.Data.SqlClient") and then execute your stuff against it.
For SubSonic 2 - SharedConnectionScope is what you want.