Value Change listener method hint

Here is an important fact. Amazing even.

If you have ever experienced where you have a difference in the behavior of your ADF Faces screen between when somebody when you do a commit by executing the commit Action binding, or doing a commit by pressing a commandLink which fires an action binding...I have some help for you.

In my (sample) senario, I had changed a name in the Name field on a screen. I wanted to get this change into the database, because there is a unique key constraint in the database on the table column associated with this name field. When I create a new record, I call a pl/sql procedure to do the work, then execute a query, then go to the screen where this name field is. The name field has a default value in it, but it is important that the end user change this name field. So I put a value change listener on the name field, so that if they change the name, a commit will be fired.

The only problem was that the value change listener method is called before the value in the fields gets written to the binding layer. So you have to force it prior to calling the commit.

If you have Steve Muench's EL helper class you can do the following in the value change listener method:

EL.set("#{bindings.Name.inputValue}", valueChangeEvent.getNewValue());

Works great!

AjaxTags

As I continue to work through Deepak Vohra's Ajax in Oracle JDeveloper book, I was very impressed not only by the book (thanks Mr. Vohra!), but also AjaxTags.  I must be tag/jsp-oriented, because I tend to view just using javascript to do Ajax as being kind of messy.

It has not taken me very long to get the example in this book which demonstrates AjaxTags up and running.  There were a few gotchas.  For example, in the example there were only three javascript files which needed to be included in the jsp page using script tags with source attributes.  The book was written in 2006.  Now in 2010, using the next major version of AjaxTags there are 7 or 8 javascript files, which I had to include.   Also Vorha-ji used a "button" tag, which in my browser issued a submit.  If you are doing Ajax you don't want to use a button that automatically submits, so I switched to using an <input> tag with a type attribute with the value of "button".

With this example I could register a select list and a button to do Ajax transactions with (in the jsp) only the following two tags:

<ajax:htmlContent baseUrl="formservlet" source="catalogId" target="validationMessage"
parameters="catalogId={catalogId}"/>

<ajax:updateField action="updateForm" baseUrl="formupdateservlet"
parameters="catalogId={catalogId}" source="catalogId"
target="journal,publisher,edition,title,author"
parser="new ResponseXmlParser()"/>

So, in this example, you had to define two servlets, one called formservlet and one called formupdateservlet.  The ajax:htmlContent tag above made it so that if you changed the selected value of a select list with the id of catalogId, it would "doGet" on formservlet with the request parameter which has that selected value.  The value of the element with the id of "validationMessage" (as specified in the ajax:htmlContent tag above) is set to the text of the response of this servlet.  That is a lot of meaning to pack into a little tag...but that "meaning" is just what we want, time and time again...isn't it...with AJAX.

The second tag, ajax:updateField, keys off of a button whose id is updateForm (see the action attribute of the tag above).  This button click does a doGet on formupdateservlet, again passing the parameter of the current value of a select list with the id of catalogId.  The target attribute is a comma-delimited list of element ids in our form of various fields we have.  This servlet (formupdateservlet) produces XML, unlike the formservlet, which just produced text.  So we specify a parser in the tag above to handle the XML.  I think then that you just have to make your servlet produce elements which match these target element ids.  Again...very compact...but exactly what we are looking for.  The only javascript involved is the script tags which include the AjaxTags javascript libraries.  These are the ones I had to include:

<script src="prototype.js" type="text/javascript"></script>

<script src="scriptaculous.js" type="text/javascript"></script>
<script src="overlibmws.js" type="text/javascript"></script>
<script src="effects.js" type="text/javascript"></script>
<script src="controls.js" type="text/javascript"></script>
<script src="ajaxtags_controls.js" type="text/javascript"></script>
<script src="ajaxtags_parser.js" type="text/javascript"></script>
<script src="ajaxtags.js" type="text/javascript"></script>

Scriptaculous is used to make some of this happen, and is part of AjaxTags.  It has some support javascript files which I did not include.  It would probably be safest just to include all of them, since there are not that many.

That's it! 

I would like to explore this a bit more (since this example does not begin to cover AjaxTags functionality fully) and see how it performs when incorporated into JSF pages.

Continuing to look at Task Flows

I have a question now about Task Flows in Oracle ADF Faces/Bindings 11g.  I see from reading Frank Nimphius and Lynn Munnsinger's new ADF book, how you can make two page fragments talk to each other by creating an event map in the parent page's pageDef, and then raising events in one fragment's bindings, and "consuming" these events with a backing bean method in the other fragment.


What still does not make sense to me is...how does the binding know what event to raise?  Granted:  I am still messing with ADF Faces 10g, but af:tables, af:tree's, etc. have more than one event associated with them.  And yet in this book I do not remember reading a description of how and event raised in the binding knows what kind of event to raise...


For example if I select a node on a tree and that triggers a context event, and then I expand a node on a tree and that triggers a context event (if that is possible...?), where does the link occur between the binding event and the particular component event?


This has more to do with events and production/consumption of them across bounded task flows for page fragments. The example in the book is as follows. On a page there is a panel splitter. On the left side is a tree with deparment nodes and employee nodes under each department node. On the right side is either a department or an employee data update screen with fields and a save buttons. The selection of a dept or emp node on the left gives you an update screen on the right with the correct row queried up. The left and right side are both regions with bounded task flows inside containing page fragments. the parent page (the one with the splitter) has the task flow bindings on it, plus it has the event map defined on the task flow bindings.

So the part I am confused about currently is when you click the tree and the tree binding raises an event, you just enter in the page def for the tree the xml element <events> with and <event> sub-element in it. In the event map you map this event producer to the consumer page/bindings on the right to get a sub-dynamic task flow to either show a emp or dept page fragment. But I do not see where it says what kind of event is getting generated. Surely a tree node can generate more than one kind of event. for example a node can be clicked/selected. Also a node can be disclosed/opened or closed/shut/collapsed/whatever.

I think the following comes close to answering my original question (taken from FUSION DEVELOPER'S GUIDE 11g):

You can raise a contextual event for an action binding, a method action binding, a value attribute binding, a tree binding, a table binding, or a list binding. For action and method action bindings, the event is raised when the action or method is executed. For a value attribute binding, the event is triggered by the binding container and raised after the attribute is set successfully. For a range binding (tree, table, list), the event is raised after the currency change has succeeded. Value attribute binding and range binding contextual events may also be triggered by navigational changes. 

Contextual events are not the same as events raised by UI components. For a description of these types of events, see the Oracle Fusion Middleware Web User Interface Developer's Guide for Oracle Application Development Framework. Contextual events can be used in association with UI events. In this case, an action listener that is invoked due to a UI event can, in turn, invoke a method action binding that then raises the event.

What is confusing to me is the documentation says you can associate an event with bindings of different types, and that the binding-associated events are not the same as ui component-associated events. But then they turn around and say that these binding-associated events all happen in response to actions for which there are component listener properties. So I naturally would assume that we would then says that...these binding-associated events are raised in direct response to the corresponding component event.

From a high level, anyway, it appears that for these binding-associated events we are triggered by a particular event in association with that binding. For range bindingg (tables, trees) the big event is changing of "row currency". (OR POSSIBLY NAVIGATION). Action/Method: when the thing is executed. Attribute -- when the value is set. So I guess the payLoad is different in each case? For the row currency, is the default payload the row? I think for the action, the payload is whatever the action or method returns...? the attribute...the new value? More reading...