gwtrequestfactorygwtpgwt-editors

GWT Editors: How to record changes to fields and sub-editors? (RequestFactory?)

I have an app that makes extensive use of the Editor Framework. Right now I'm at the point where I want to add a new feature: if a user edits an entity, I'd like to record which changes were made and store them in a separate datastore entity. This requires knowing if a field was changed, the field name, and the value it was changed to.

This is what I'd like to implement:

  1. App calls edit(bean);
  2. User makes changes, calls flush() and data gets sent back to server.
  3. In server handler, changes from the bean are sent to processChanges(List<String> paths) which then creates and stores the record that "field foo" was changed to "bar", and so on.
  4. The entity is saved, overwriting the existing one.

I use GWTP and currently use the RPC Command Pattern. I've read a bit about RequestFactory and as I understand, one of its main benefits is that it only sends the changed fields known as "deltas" back to the server to minimise the payload, so I'm wondering if using RequestFactory would be a better fit for my app?

Apologies - I've been reading through the GWT docs and Javadocs for the Editor Framework and RequestFactory but I'm still pretty confused. RequestFactoryEditorDriver.getPaths() seems like it might be what I need but any advice or pointers greatly appreciated.

I could probably watch for changes client-side but that seems like a bad idea.

Solution

  • I believe you could do that using an EditorVisitor, similar to the DirtCollector visitor used internally by the Editor framework (have a look at the PathCollector for how to collect paths in a visitor).

    I would start by visiting the hierarchy to collect the initial values just after the call to edit() (this is done already by the DirtCollector internally, but there's no way to access its results, and it only collects leaf values anyway).
    Then you could call flush() ans see whether there are errors, and possibly validated your object to see if everything's OK. Then you visit the hierarchy again to collect the changes (against the initial values you previously collected) so you can send them to the server.