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.
Related
I have been working on a project. I always followed this idea. Don't send all the data in one call.
Here is an example,
Suppose there is an API to return all the list of students that can be added to test they need to finish.
So, on UI side every student have one button "add" which will show a pop up if the student is already assigned to take the test. Or it will show a pop up he has already finished the test.
I could join many table and send all the data in one api call while fetchig students. Or
I could send the send the students and then on "add" there is another API to make sure the above mentioned conditioned met.
Which approach is better?
Because If I send all the data in one api call, there might be only few students be assigned the test.
Checking if a student is already assigned or not should happen in the backend, not frontend, and also atomically so as to prevent duplicates - either using a database transaction or a unique constraint.
When the Add button is clicked then in any case a backend call will need to be made (to perform the actual Add). If the add failed, the backend can interpret the "unique constraint violation" database error and return a "student is already assigned" message.
For the rest of the question, the rule is simply: don't fetch more data than is required by the UI.
If the Add button is always shown regardless of whether or not the student is already added, there is no need to retrieve this information beforehand.
But it might be useful to give a visual indication of which students are already added, in that case obviously there's no choice but to retrieve and return this information to the UI.
Fortunately GraphQL is precisely the tool for this job - it makes it possible for the UI to request exactly what information is needed for a given page, without having to code each and every possible query by hand.
I have a Case View which shows all the records that were created by the me (My Cases view). I now want to all those Cases edited/modified by me to be visible in that view. The problem is those modified by me could be later modified by the system when a workflow updates the Case, which changes the Modified By User data. Thus, not allowing me to use Modified By (Current User) as a condition for the view.
Is there any other way or condition which I can use to make sure the I can accomplish this?
Thank you in advance.
You may create a new Entity with One to Many relationship with Case Entity. Whenever there is Insert or Update you can add a new record in the mapping entity with Modified By Information and Created On OOB.
You can create a view in the new entity with record modified by Me.
P.S - Single case record will be edited multiple times with multiple users so it will result in high volume of data and may want to look for archiving strategy.
There is custom field "Lock Flag" in Account BC, namely in S_ORG_EXT_X table. This field is made available in Opportunity BC using join to above table. The join specification is as follows: Opportunity.Account Id = Account.Id. Account Id is always populated when creating new opportunity. The requirement is that for newly created records in Opportunity BC if "Lock Flag" is equal to 'Y', then we should not allow to create the record and we should show custom error message.
My initial proposal was to use a Runtime Event that is calling Data Validation Manager business service where validation rule is evaluated and error message shown. Assuming that we have to decide whether to write record or not, the logic should be placed in PreWriteRecord event handler as long as WriteRecord have row already commited to database.
The main problem was how to determine if it is new record or updated one. We have WriteRecordNew and WriteRecordUpdated runtime events but they are fired after record is actually written so it doesn't prevent user from saving record. My next approach was to use eScript: write custom code in BusComp_PreWriteRecord server script and call BC's method IsNewRecordPending to determine if it is new record, then check the flag and show error message if needed.
But unfortunately I am faced with another problem. That joined field "Lock Flag" is not populated for newly created opportunity records. Remember we are talking about BC Opportunity and field is placed in S_ORG_EXT_X table. When we create new opportunity we pick account that it belongs to. So it reproduceable: OpportunityBC.GetFieldValue("Lock Flag") returns null for newly created record and returns correct value for the records that was saved previously. For newly created opportunities we have to re-query BC to see "Lock Flag" populated. I have found several documents including Oracle's recomendation to use PreDefaultValue property if we want to display joined field value immediately after record creation. The most suitable expression that I've found was Parent: BCName.FieldName but it is not the case, because active BO is Opportunity and Opportunity BC is the primary one.
Thanks for your patience if you read up to here and finally come my questions:
Is there any way to handle PreWrite event and determine if it is new record or not, without using eScript and BC.IsNewRecordPending method?
How to get value of joined field for newly created record especially in PreWriteRecord event handler?
It is Siebel 8.1
UPDATE: I have found an answer for the first part of my question. Now it seems so simple to me that I am wondering how I haven't done it initially. Here is the solution.
Create Runtime Event triggered on PreWriteRecord. Specify call to Data Validation Manager business service.
In DVM create a ruleset and a rule where condition is
NOT(BCHasRows("Opportunity", "Opportunity", "[Id]='"+[Id]+"'", "AllView"))
That's it. We are searching for record wth the same Row Id. If it is new record there should't be anything in database yet (remember that we are in PreWriteRecord handler) and function returns FALSE. If we are updating some row then we get TRUE. Reversing result with NOT we make DVM raise an error for new records.
As for second part of my question credits goes to #RanjithR who proposed to use PickMap to populate joined field (see below). I have checked that method and it works fine at least when you have appropriate PickMap.
We Siebel developers have used scripting to correctly determine if record is new. One non scripting way you could try is to use RuntimeEvents to set a profileattribute during the BusComp NewRecord event, then check that in the PreWrite event to see if the record is new. However, there is always a chance that user might undo a record, those scenarios are tricky.
Another option, try invokine the BC Method:IsNewRecordPending from RunTime event. I havent tried this.
For the second part of the query, I think you could easily solve your problem using a PickMap.
On Opportunity BC, when your pick Account, just add one more pickmap to pick the Locked flag from Account and set it to the corresponding field on Opportunity BC. When the user picks the Account, he will also pick the lock flag, and your script will work in PreWriteRecord.
May I suggest another solution, again, I haven't tried it.
When new records are created, the field ModificationNumber will be set to 0. Every time you modify it, the ModificationNumber will increment by 1.
Set a DataValidationManager ruleset, trigger it from PreSetFieldValue event of Account field on Opportunity BC. Check for the LockFlag = Y AND (ModificationNumber IS NULL OR ModificationNumber = 0)) and throw error. DVM should throw error when new records are created.
Again, best practices say don't use the ModNumbers. You could set a ProfileAttribute to signal NewRecord, then use that attribute in the DVM. But please remember to clear the value of ProfileAttribute in WriteRecord and UndoRecord.
Let us know how it went !
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
I have a custom entity in Microsoft CRM (4.0). The user has to input records however usually they have a batch of 20+ records that are almost the same apart from 2 or 3 fields which need changing. I know I need to write some custom code to enable this functionally. However can anyone recommend any methods to do this.
Ideally there should be a button that will save and create a copy as a new entity.
My Current way of thinking is to pass all the details as part of the URL and use javascript to strip them out on the page load event. Any ideas welcome.
Thanks
Luke
I found the answer here:
http://mscrm4ever.blogspot.com/2008/06/cloning-entity-using-javascript.html
I've used it and it appears to work well.
Since there are numerous fields, but only certain fields values are different, then i am thinking to set the default value to all the fields, so that users just need to alter those values when needed.
In my approach, i will hook a javascript function on load of the form data entry screen and use XmlHttp approach/Ajax approach to hook to the custom web service to pull/retrieve the default values of each fields. Or you can set those values at the javascript function itself, but the drawback of this, it's difficult to customize later. So i will choose the approach to hook to the custom web service and retrieve those value from some application parameter entity.
Your idea of providing a "clone" button is also a great idea, which means that it will duplicate all the attributes of the previous record, into a new record, so that it will save time for data entry person to customize the different value
EDIT
Since you would enter records in batch mode, how about customizing .ASPX screen to enter records. By customizing through .ASPX screen, you can use a tab , so that users can browse through tabs, to customize the value/attribute of each record.
There will be a "save" button as well as "clone" button to clone some common attribute or value.
I would create a custom web service that would accept the entity type and the ID of the record I'm cloning. Your "Save and Clone" button would call the service, and the service would handle the details of retrieving the current record and deciding which fields to set on the new record. The service creates the record, and sends the Guid of the record back to your button, which then opens up the newly created record.
This way, you avoid the messiness of setting/getting values in JavaScript and tying which fields to set/retrieve directly to your OnLoads, as well as avoiding the possibility of query string that's too long.
The service could easily be sufficiently generalized so that all you'd have to do is add your button to any entity, and it would work, assuming you'd set up your service to handle that particular entity.
One possible downside is that since the clone record button would actually create the record, the user would be forced to delete the cloned record if they decided they didn't want to clone the record after all.