i have created a booking system which synchronizes with Google Calendar every 5 minutes and also truncates and old data and fetches new one from calendar, this process takes about 2-3 seconds.
What i want to do is, when the event to fetch data from Google Calendar fires, i want to disable access to the route of the booking system for these 2-3 seconds then enable it again when the event ends, i want to do this because it truncates the old data and fetches new one, so if a person is looking at the booking system this 2-3 seconds all the book schedule times will be free and i don't want this to happen.
Is this kind of thing possible?
Thanks and regards!
Well, my suggestion is to create a new field in your users table something like : is_google_sync_active and route middleware.
Then just before you will start sync. you change that field to true and in your new middleware you may check whether your sync. is active or not, then when your sync. ends you just change the value of field again to false. So, every time when user tries to pass to your sync route he will be passing your middleware which wil handle all job.
In addition, you can redirect user to page which shows status or progress if the sync. is processing.
i am using Spring/Hibernate/ZK. In one tab i get object from DB for editing by user, but second user can open the same tab and the same object for editing . I want to informed second user whit message like "This object is аlready open" and hide buttons for save.Тhus second user can see current data from DB to this object but can`t edint him.Is there a way to check session for this object or another way to do that.
The other answers mostly look at the database, but if all users use the same zk application to access the database, you could keep track of opened objects in the Composer or ViewModel (depending whether you use MVC or MVVM; I'll just call it controller).
Your controller would need a static list of objects that are currently modified. If a user requests to open an object that is not in the list, everything is fine and your controller enables the fields and save button. Otherwise, those are disabled and/or you display a message.
The tricky part is clearing objects from that list. If a user presses the save button, you just remove the object from the list. But what if the user doesn't and just closes the tab or their session just times out? In this case you need a callback, or a mechanism that regularly checks whether the screen is still open.
You could achieve this by adding a zk timer to the tab that pings every now and then and updates the timestamp in your static list (so make it a map). If a new user tries to edit the object, check how old the last timestamp is. If it is old enough (i.e. the previous user saved it or abandoned the screen), allow them to edit it.
Still, you have to think about what to do if a user just keeps the screen open. How long are they allowed to keep the lock on the object? This is an issue in Microsoft Office as well. If multiple users try to open an Excel file from a network location, the first one gets to lock and the others cannot save until that user saves.
You may have additional field which indicates that column is being edited. When first user starts work, the field would be updated. The second user would query object with 'on hold' status and your code would handle this.
Other way - use Hibernate #Version field in your entity. It holds object version which is incremented after every update operation. If second user would save object after first one already saved, it would throw OptimisticLockException which you could handle in your code. More about optimistic and pesimistic locking: Chapter 5. Locking. Related discussions: Hibernate Automatic Versioning and When to use #Version and #Audited in Hibernate?
The best solution is to use Optimistic Concurrency Control with Versioning and when Hibernate throws Concurrency Update issue due to same row is being updated in two transaction then use one of below strategy
First Wins Strategy
Last Wins Strategy
Merge Conflicting Update Strategy
First Wins Strategy is not good solution as it leads to lost update and user will get frustrated that all his work is lost.
By Last Wins Strategy one of user will get error message that you are working on Stale data and start your transaction again . By this way also user can get frustrated due to fact that now again he need to restart operation from beginning but his changes will not lost.
Instead go with Merge conflicting Update Strategy, when Hibernate throws Stale object exception reload screen with new data and user will see updated result and allow him to proceed with latest data. In this user changes will not loss and user will not get error message , just his screen reloads with fresh data and he can decide whether to proceed or not .
You can take example any e-commerce site and you will get one of result of either Last Wins Strategy or Merge Conflicting Update Strategy. Two user can start to by one item but one of user will get message in last screen that item is not stock.
In my workflow I have iterative loop which check the table value until it matches a workflow value using DB Execute.
This stage arise after completing initial and step After values matches it will proceed to next step.this has created by adding delay function.
However my client required to show the list work items which are pending withing content navigator. Is there a way to achieve this.
Try to add users (who want to track status) in F_Trackers system Workflow Group.
I have a Master Detail form in my Oracle APEX application. When I am trying to update data in this form, I am getting below error.
Current version of data in database has changed since user initiated
update process. current row version identifier =
"26D0923D8A5144D6F483C2B9815D07D3" application row version identifier
= "1749BCD159359424E1EE00AC1C3E3FCB" (Row 1)
I have cleared browser cache and try to update. But it not worked.
How can I solve this?
I have experienced similar problem where my detail records set has timestamp fields. By default master detail wizard creates the timestamp fields as date picker type fields. If you set the date format on these, it would resolve the issue.
This blog post tries to address this issue on a Tabular Form (I know that's not what the original issue was with, but thought it might be related). It says the same as #sangam does below.
Short version: If you have an updated field that's timestamp datatype, you should set a date/time format.
http://apexbyg.blogspot.com/2015/05/tabular-form-bug.html
My tabular form has a field that's timestamp datatype, but I had already set a date format, so this didn't help me.
Here's another possibility, which I discovered was the case in my application.
That would be if the data the original checksum was calculated on is truly different than the pre-update checksum calculation, due to a design-flaw in your query!
In my application, the source for one of the updateable fields was COALESCE(name_calced, name_preferred). In the source table, the person's name could already be loaded in the record by an external process and we save it to one field - name_calced. But the end-user can enter a preferred name, which we wanted to save to the name_preferred field. We wanted to initially populate the displayed, updateable tabular form field with name_calced, if one existed, or name_preferred if the user had already provided a preferred name. Then they could change that value and save it back to the database.
I finally discovered that the Save action threw the error message if name_calced was non-null, but name_preferred was null. I realized that the initial checksum was calculated based on name_calced, but the pre-update checksum was based on name_preferred, so the application thought someone had changed the value in the background and showed the error message.
What I don't understand is how this problem didn't show up in the past 3 years the application has been running in production!
My solution is to make the field source only on name_preferred, which immediately solved this problem. I also think the back-end process will also get changed to pre-populate that table field from name_calced, so the user always sees the base value, if there is one.
I just had this issue myself. Now, I realize that tabular forms are deprecated at this time, but I have an application that was developed beforehand and still uses them. This issue occurred and I had to get one of our big guns at Oracle to help me out. I do a lot of DB work and a decent amount of Apex development but I'm more of a Java, WebLogic, etc guy, and I really couldn't figure this one out.
In my case, it turned out to be really simple. One of the columns in my tabular form was a hidden field, generated via a sub query. Being hidden, this column is not editable by the user and should not be part of the MRU update. I had the field set to "Hidden Column (saves states)" and setting its type to "Hidden Column" fixed the issue. So, this leads to sub queries being executed in such a way as to change the checksum for the overall query before hitting submit (save), causing the error.
For those who are continuing to troubleshoot this, look at your query for every field that you have specified and note which columns are editable in the tabular form. All other fields should be set in a way that makes them not save state so that they are not part of the update.
I had this error when I had two update processes processing on submit.
My solution was to add a condition to both processing steps. I had forgotten to do this when I made an additional process for Button A, but I never updated Button B to limit it's behaviors.
Navigation:
Processing -> Processes -> [Your Process Name] -> Server-side Condition -> When Button Pressed = [Your button Name]
In my case I had a column from a secondary table that was not set as Query Only and was being updated! The error would occur trying to save a column not in the table being updated. It took me half a day to figure it out (the column names were the same).
Set your Link column hidden to display only in the form.
Set "Send On Page Submit" to 'No' or disable the link column that is your primary key ( Rownum/rowid/id etc).
Hope it will work for you.
I have noticed this error comes when I was working Tabular Form and has disabled one of the form operations i.e. by setting server-side condition to "Never" for add, apply changes (submit) buttons
When I have restored back to its original state, it worked as expected.
In case you have to hide Add/Update button, use some other option.
https://compknowledgebase.blogspot.com/2018/12/oracle-apex-error-current-version-of.html
Let me describe the problem in detail.
I have a table called export. Which has a field job_no.
When a user comes and fills this query run
select max(job_no) as Last_Job from jobs
The result is A005 which is the last job number in the table.
On the PHP end I display A006 in the entry form which user is going to fill and submit.
The job_no field in the form is read only and user can not change it.
Now here comes the problem if multiple user are filling the form at the same time A006 is being displayed to each and when they submit the form A006 is submitted with their record.
Which is duplicate and is not required.
Now what should be the solution to prevent this situation.
I have three solutions but i want to know if there is some better solution.
Solution 1
I insert the job number to user_entry form with user id and display it to user.
Then when user submits the form i update it.
Draback seems that if user cancels the form submission the job_no is useless then.
Solution 2
I display the job number to each user and when submitting i check the job number , increment it and tell the user that the job number has already been assigned so he is going to be assigned the next one.
if i don't display the prompt message to user he will be under the impression that his job number is A006 where in the database it will be A007.
Also if i run ajax request with setInterval it will be a load on server and there is still chance of duplicate.
This is necessary to display the job number to the user. So what is the better approach in this situation. Or is there any alternative to this problem?
Why do you display A006 to the user before they create the form? I fail to see how that can be a "requirement" if you can use solution two which says you can change it anyway.
Why dont you just get them to fill in the form, and when they submit say "thanks - job A006 has been created". Simple and easy