I've an issues with the Kendo datasource.
I read the data then I works on dataitem and so I sync the datasource, it is working well and datas are well saved in DB.
But if I works on dataitem after the sync and I cancel changes, the datasource back to the read state and not to the sync state.
So how to sync data and commit state without ask a read after a sync ?
Thanks for your help.
Are you experiencing this for all scenario's (Create/Update)? You should not have this for Update but can face this for Insert if your service is not sending newly generated Id's back. (Hope you have a Id for your model). Once you have the Id you can add that to your grid source. I have done this few months back but don't have the code now.
May be this post can give more detailed information http://www.telerik.com/forums/refresh-grid-after-datasource-sync
Related
my form is saving the data as individualy but when I link it with side by side form it shows the success message doesn't create or update the record in table. Please help. For this purpose I can share my application credientials as well.
Hi, my form is saving the data as individualy but when I link it with side by side form it shows the success message doesn't create or update the record in table. Please help. For this purpose I can share my application credientials as well.
I am working on a JSF project that deals with MySQL DB.
in my backbean method I did:
entityFacade.edit(entity object);
after that I wanted to make sure of the changes, I queried my database to retrieve the edited record, However, the retrieved values are the old ones. it is like entityFacade.edit(entity object); was not made.
I solved this problem by doing this
entityFacade.remove(entity object);
entityFacade.create(entity object);
But the problem is that the object has ID which is auto-increment & I want to keep the old ID.
I don't get why the edit does not change values. what are the possible causes of this problem?
Looking forward to your answers, experts.
For those who are facing the same problem, I solved it as follows:
The problem was not with the facade.edit()
it was with the queries.
Try facade.find(id) to retrieve the records from the database instead of queries. The retrieved records will show the edited data.
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.
I have a Spring 4 and Hibernate 5 back-end RESTful web-service. This works great and is all unit tested. The front-end is a SmartGWT 5.0p application which uses DataSources, not RestDataSources to communicate with the back-end.
The front-end SmartGWT 5.0p uses a listgrid to edit data, and then the ListGrid is attched to a datasource. Only the edited data in the ListGrid is sent back, not the entire row. If I could, I'd like to be able send backthe entire listgrid row with edited data, and the unedited data. If I could get an answer to that, that would be great.
Or, the alternate is we let SmartGWT only send back part of the data which is edited. This comes to the back-end as JSON and is changed into an Object/Entity. The controller/end-point is not in a session yet, but then we call a method in the service layer which is transactional.
So, then question becomes we have a detached object in a session in the method in the service layer. We have a detached object with a database primary key ... but it also has 1 or 2 fields of updated data, and now we want to merge that data back to the database. We can't call an update with this entity because with the partial data, some of the fields are being set to null. In reality, we want to pull back the item from the databae, update the edited fields, and then write the data back to the database.
I could do this all manually ... but do I have to? I expect there is a more graceful way to handle this.
Thanks!
This is only a partial answer:
I can make SmartGWT combine old values and new values with a link I found here:
SMARTGWT DataSource (GWT-RPC-DATASource) LISTGRID
And the code is as follows:
private ListGridRecord getEditedRecord(DSRequest request)
{
// Retrieving values before edit
JavaScriptObject oldValues = request
.getAttributeAsJavaScriptObject("oldValues");
// Creating new record for combining old values with changes
ListGridRecord newRecord = new ListGridRecord();
// Copying properties from old record
JSOHelper.apply(oldValues, newRecord.getJsObj());
// Retrieving changed values
JavaScriptObject data = request.getData();
// Apply changes
JSOHelper.apply(data, newRecord.getJsObj());
return newRecord;
}
This JSON string contains the new fields updated, and the old fields. When this json string is sent back to the RESTful back end, the Jackson Mapper creates an entity and puts all the fields in, this is essentially a detached entity. It's an object outside of the session, but the id resides in the database.
Because I have a complete entity, I can all an update, and that works.
Problem solved.
BUT, I'd still like to find out an elegant solution for taking a detached entity, get the original record from the database, and then merge these two objects, and then finally update the record.
In the Service layer in Spring which has a transaction, and creates the session,
a manual process, which I don't want to do might look something like this:
1) get the id from the updatedEntity
2) get that attachedEntity from the database using that id
3) compare the fields
if( updatedEntity.updateField1 != null )
{ attachedEntity.setField1(updatedEntity.updateField1) }
If I had to do step 3 for multiple fields,
that's not very elegant.
4) Update attachedEntity to the database, because it now has updated fields.
So, again, an elegant solution to fix this might be helpful. Thanks!
I am using mvc3 for my web app.
When an user edit an existing form, make a few changes and save it.
what is the best practice to check which field in the form has been modified.
Regards,
Bubblegum.
Since we're not talking data access - upon postback, compare it to your object in your database. This is somewhat of an open question because it depends what data access you are using and what models you are using. Entity framework Entities can track their modified state so you may be able to use
TryUpdateModel(yourInstanceLoadedFromYourDatabase)
and check the status of each field. That 'may' work, otherwise you are comparing each field. However why do you need to know specifically which field changed? Save the entire object back to the database (or simply merge with the values from the page using the same TryUpdateModel above)