Yes, but WHAT IS A CONTROLLER??

I asked Simon Lessard (a guru among gurus for Java and ADF) in the ADF Methodology Group about what he thought a controller was, and his response is of great interest to me; so I am going to publish it.

From it I learned that Struts did not use the event model, what an Observer pattern was, and a better way to organize your backing bean (controller bean/data bean) code.

From this thread, we have the following:

Hi Michael,

It depends, "controller" can have many meanings. In the purist version, the MVC model is a triangle (http://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller). The model exposes the data and services, the controller is the one in charge of calling the model, and the view represents it, calling the controller whenever a UI event occurs and observing (observer pattern http://en.wikipedia.org/wiki/Observer_pattern) the model layer for change and updating itself if something happens.

Now, since the Web model is a detached one, that last interaction is not possible so the MVC model in the Java web world is a mutation of the pure one. As of Struts, the controller was defined as the component in charge of managing the page flow, the navigation of which was implemented by two type of entities, the Action and the struts-config.xml file (and the control flow engine running it). With JSF, the event model like that of Swing was added, providing a way to implement another part of the controller layer -- the UI event management -- through various listeners. Each listener can therefore be considered a controller or part of a bigger controller (depending how you implement it) since these listeners can modify the component (refresh it, change its state, etc.). Also, since those listeners are accessed through EL and call managed bean methods in the end, then yes, I consider some managed beans a controller (or a part of a controller) -- but only if they are not used to store data. I call the latter data beans, and they often implement an interface from the model layer so that they can be used as service call parameters. So, in the pages, you have:

<af:inputText value="#{expressionToADataBeanField}"/>
<af:commandButton action="#{expressionToAControllerBeanMethod}"/>
<af:someComponent binding="#{expressionToAControllerBeanField}"/>

Since the controller bean often needs access to the data bean, I inject the data bean into the controller bean (using the managed-property feature of JSF) when the controller is created. The data bean is stored in a persistent scope like session or page flow and must therefore be Serializable. The controller bean, on the other hand, must be stateless; so it can only be placed in the backing bean or the request scope and cannot be Serializable since UIComponent (the root class for components) isn't and can be bound in the bean.

So yes, I call a backing bean a "controller" since they manage the UI interactions, call the model layer services and participate in the navigation through the action's outcome which is everything a controller should do. However, the controller layer is also completed by the JSF's NavigationHandler, which takes care of the actual page flow from the outcomes.

So to summarize, I consider:
- Managed beans used to bind components and deal with events: backing beans, controllers, controller beans
- Managed beans used to store the data entered by the user: data beans, page flow beans, session bean


I hope it clarifies the concepts a bit,

~ Simon

Backing Bean Scope

What is a key difference between JSF request scope and ADF backing bean scope?

Well, the "lifetime" of these two scopes is exactly the same. However if you need to create a backing bean for an ADF declarative component, the you will need to use backing bean scope for that managed bean. This enables using multiple instances of your declarative component in a single ADF page...something which the JSF request scope does NOT support.

(Please see the comments on this blog entry for an additional function of Backing Bean Scope as relates to regions and bounded task flows; many thanks to Chris Muir for pointing these things out.)

Refresh Data Controls in JDeveloper 11g

If you are looking on your ViewController project and you do not see new columns you have added to your business components, press the refresh icon on your Data Controls pane. It is very important...this is not just a convenience...to hurry something along that just has not happened yet in the due process of polling or whatever other triggers might be used in the inner sanctums of JDeveloper. This refresh action is more like, the View does not even recognize the changes until this refresh button is pressed.

Perhaps it is just the way I am using JDeveloper, but this seems to be a very helpful thing to know, if you are used to JDeveloper 10g.

JSF 2.0 observations on JavaScript format for Ajax

I notice that on the version of JSF 2.0 I have on GlassFish, that the jsf.js page may not be included to make a call to jsf.ajax.request(), if you need access to this function. I guess in that case you would either add a do-nothing f:ajax tag to your JSF file, or do some include of the jsf.js library programmatically. The former option may be better.

Also I noticed that if you want to key in on a non-default event when calling jsf.ajax.request() that you will need to create an object for the last parameter that includes the property javax.faces.behavior.event...but be careful: you will get a JavaScript error if you try to do this all in line without some extra work. Property names typically do not have periods in them ("."). So you have to do something like the following:

...onkeyup="var lArgs = {}; lArgs['render'] = 'form:output'; lArgs['javax.faces.behavior.event'] = 'keyup'; jsf.ajax.request(this,event,lArgs);"

I am currently in the best seat in an IMAX 3-D version of Tron Legacy!!!! Been waiting most of my adult life for this sequel. Lol...

JSF 2.0 paper coming

I am on the hook to present JSF 2.0 New Features presentation to the NoVAJUG February 17 or so. It should be fun. JSF 2.0 is really cool. I will publish this presentation to slideshare when I get it fleshed out.

J-Integra

On the project I am at now we are using a product called J-Integra for COM. It allows us to control Excel (in our case...probably any MS Office tool) through DCOM in Java. We tried things like Apache POI and Actuate BIRT Spreadsheet Engine/API first, but the spreadsheet we had to control had visual basic macros in it which called C++ DLL's. And Java does not (yet) understand anything about VBA, so those efforts did not work for us.

The set up of J-Integra is fairly minimal. There is a license xml file which is emailed to you upon request, and you must rebuild their product's JAR files using their JAR rebuild command. Then you have 30 days.

At that time you can run something called comtojava (I think) and it generates a great many java/class files which do the DCOM calls. There are also a lot of interfaces in there defined.

The result is that you can open/create a workbook, manipulate it, and close the book. The opening actually opens a copy of Excel, so you have pretty much complete API access. It is almost like a testing tool.

Hope this helps.

kudos to JSF 2.0's f:ajax tag!

It has been verging on too long since my last blog entry.

I have been reading in JSF 2.0: the complete referece by Burns, Schalk and Griffin about the f:ajax tag, and the Ajax implementation in JSF 2.0.

It's really cool.

Here is my background with Ajax. I have implemented Ajax solutions in JSF apps using straight JavaScript. This was kinda hard but not too bad actually. But I am fairly comfortable with JavaScript. I have also worked with the JSF Blueprint auto-suggest component. This worked out rather well and hid much of the details of the JavaScript functionality behind a JSF component. I have also studied a bit more than half of Deepak Vohra's book Ajax in Oracle JDeveloper and seen what a huge number of ways there are to do Ajax...and that is just with Java! I have also been working with ADF 10g's PPR solutions and my own frame/iframe kluges for years as well.

I really like the simplicity of the f:ajax tag. For starters, I love that you can get some basic, useful Ajaxian functionality simply by including the f:ajax tag either inside or wrapped around you JSF tags! This basically would do the equivalent of submitting those fields when the default event for those JSF components fires. The default JavaScript client event for a component is a sensible value depending on whether it is an action component or a value-change component.

Then it is possible to have all the flexibility of doing Ajax from raw JavaScript.

It is certainly much much easier than having to construct a bunch of JavaScript then do a bunch of request hijacking from a PhaseListener, like in JSF 1.1 and 1.2.

Thumbs way up guys!

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.