How do I check which values in my Form have changed before saving?

The situation is like this. We have a form with a large number of fields (over 30 spread over several tabs) and what I want to do is find which values have changed before saving with min开发者_如何学Cimum impact on performance. What happens right now is, for editing, single records are queried from several databases. The values are passed over to the client side as value objects. At the moment they are not bound to any fields in the form.

My initial idea was to have a boolean flag for each field to set true or false each time any of the fields were changed. At the time of saving the program would run through the list of flags to see which fields have changed. This seems more than a bit clunky to me so I was thinking maybe it could be done on the server side. But then I don't want to go through each field one by one checking to see which ones don't match the db records.

Any ideas on what to do here?

This is a very common problem for a lot of Flex applications. Because it happens so often there are a number of commercial implementations for Data Management. Queries are stored into entities and those entities are bound to a form on the client side. Whenever a field is updated, it will automatically perform the steps to persist the changes to the db and do rollbacks when requested.

Adobe LCDS Data Management - If you are dealing with a Java environment WebOrb - If you are dealing with a .net, php, java, rails environment

Of course you can re-invent the wheel and roll out your own, set up PropertyChangeEvent listeners on each field. When the changes are dispatched, listen for them and write handlers for each one.

This sounds exactly like what we're doing with one of the projects I'm working on for a client.

What we do is dupe the value objects once they back to the UI. Then when calling the update service, I send both the original object and the new object. In the service, I do a field by field compare on the server to determine what values should sent to the database.

If you need to update every field/property conditionally based on whether or not it changed; then I don't see a way to avoid the check with every field/property. Even if you implement your Boolean idea and swap the flag in the UI whenever anything changes; you're still going to have to check those Boolean values when creating your query to determine what should be updated or not.

In my situation, three different databases are queried to create the value object that gets sent back to the UI. Field updates are saved in one of those database and given first order of preference when doing the select. So, wee have an explicit field by field comparison happening inside a stored procedure.

If you don't need field by field comparisons, but rather a "record by record" comparisons; then the Boolean approach to let you know the record/Value Object had changed is going to save you some time and coding.