I've been doing user interfaces (UI) for a long time. I hate to say how long, because I'm looking for a new job, and I'm afraid that age discrimination is very real. And I'm also aware that behind my back some of my younger colleagues think that I'm set in my ways, behind the times, and in short, obsolete.
A little history
To be sure, my first user interfaces were a sort of template for users to enter data into a fixed record format file, The only validations were to designate fields as alphanumeric or numeric. My next applications let me draw forms on a terminal, and that gave me the ability to write (in COBOL of all things) code to validate and then write data to data files. I graduated from there to Oracle Forms. What a difference! Now I could point my tool at a relational table, even several tables in master/detail relationships, and it would generate a first cut at forms to update those tables.
Oddly, my next step was a step back - I was working in HTML and once again had to develop my own forms and write my own code to process the input and decide which tables to update and what to feed back to my users. At least PL/SQL is an easier language for that than COBOL. In about 2000, it was nice to get a hold of Oracle Designer, and its web generation capability, which would create forms for me. But then, I lost a lot of control over what the form looked like - unless I wanted to take COMPLETE control and not be able to regenerate the form from Designer,
Application Development Framework
Which brings me to Oracle Application Development Framework (ADF), ADF Faces, the view and controller part of ADF is based on Java Server Faces (JSF), which is part of the Java Enterprise Edition (JEE) standard. Oracle JDeveloper, the primary IDE for ADF, can generate first cuts at forms, but not just forms: ADF can do tables, graphs, hierarchies, trees, calendars and other data visualization. It can drill down. It can navigate from page to page, and this flow of control is shown graphically so that even showing it to a user, the user can get an idea how it is going to work.
A lot of the components have built-in functionality that I don't have to code. For instance, an ADF table component can let users reorder columns, re-sort, and filter, with no code. There are tabbed layouts, split screens (vertically or horizontally), and accordion layouts. There are popups and quite a bit of control over when a popup is displayed and when hidden. Some layout components are especially designed to rearrange themselves according to the size of the screen - showing differently on a phone than on a desktop for instance. The newest version of ADF can inform the application about the screen dimensions so that the application can decide what components to show.
ADF can do single page applications where the header, main menu and footer are all static with only the content in the middle changes. It can do AJAX, changing only the parts of the page that need refreshing.
Other JEE/JSF Frameworks
One of the arguments against Oracle ADF is that it is Oracle. And it is not open source – if you are on a support contract, you can get the source code, but you will need to sign a non-disclosure agreement and you can't change it. Many people would prefer to use open source software only, and avoid depending on Oracle.
I can't argue with the advantages of going the open source route. ADF Essentials lets me use ADF for free, and I can use an open source JEE application server. And I've written an ADF application against an open source database, so we don't HAVE to use Oracle's expensive RDBMS. But even ADF Essentials is NOT open source, and it doesn't do everything the non-free version can do on the non-free Oracle WebLogic Server. We can get away from ADF BC and use an open source JPA implementation - and if you write ADF Essentials applications with Eclipse, you probably will do that. To get away from the ADF Controller and ADF Faces to an open source replacement, you can use the base JSF controller and an open source JSF library like PrimeFaces. But in doing this, you will lose some of the wonderful tooling that JDeveloper has for code generation. Or even Oracle Enterprise Pack for Eclipse has pretty good tools for developing ADF Essentials applications with EclipseLink for the Model and ADF Faces for the View and Controller.