Manish Namdev’s Blog » 2009

The latest Java performance tips from around the web, such as “The elements of an array are not volatile, only the array pointer itself is. So defining an array as volatile does not provide you with an array of volatile elements.”

For September, GM Canada again sold more vehicles than any competitor in Canada, delivering 23,778 vehicles. Calendar year-to-date, GM continues to be Canada’s automotive sales leader. “We are very pleased with the strong retail sales performance of GM’s four core brands; Chevrolet, Cadillac, Buick and GMC with sales of these core brands up 5.6% over the same time period last year,” says Marc Comeau, GM of Canada’s vice-president of sales, service and marketing. “With our broad range of high quality, and segment leading fuel-efficient vehicles, combined with the recently announced Cash for Clunkers and the 60-Day Satisfaction Guarantee - now’s the time to visit a GM show-room and see for yourself.”

Justifying the extra investment for developing a single-purpose service – a service expected to solve only one large business problem - instead of putting the single-purpose logic inside a non-service-oriented application can be challenging. Reuse, the most popular motivation for creating services, will not apply. So where’s the business case? Acceptable justifications can include: enabling support for multiple providers, isolating logic from change, centralizing IT-support for a given business process, service composition optimization, and separation of concerns. Although performance is commonly referenced as a reason to not create services, that line of thought is not always valid.

With the help of patterns referenced from the recently published SOA Design Patterns book [REF-1] and the soapatterns.org site [REF-17], this article will delve into these issues as we explore the case for the single-purpose service.

Unlike most of my blog posts, where I try to describe the easiest possible way to do things, in this posting, I’ll instead go over a Java-based custom JSF component that responds to the Ajax tag. The reason being that there simply aren’t any examples out there of how to do this, and at least two people have expressed interest in finding exactly out how this is done. I’d advise anyone considering doing this to make really sure that you can’t do the same thing in a Composite Component (you usually can), but sometimes, a Java-based custom JSF component is going to be required.

We’re going to cover the following topics here, and it’s going to be a little more code than usual, but I suspect that this will end up saving some folks a bunch of time, so lets plow forward. I’ll cover:

Ajax listeners
Facelet components
Integrating the two

First, the Ajax Listener

An ajax listener, connected to your ajax event with the listener attribute, is a method that will be called every time the ajax request is made. For example, let’s look at the following page section:

   1 Echo test: <h:outputText id="out" value="#{custom.hello}"/>
   2 <br/>
   3 Echo count: <h:outputText id="count" value="#{custom.count}"/>
   4 <br/>
   5 <h:inputText id="in" value="#{custom.hello}" autocomplete="off">
   6     <f:ajax event="keyup" render="out count eventcount" listener="#{custom.update}"/>
   7 </h:inputText>
   8 <br/>
   9 Event count: <h:outputText id="eventcount" value="#{custom.eventCount}"/>

We’ve got three bean properties - hello (which is the string entered by the inputText), count (which is a count of the characters in hello, and eventCount (which is a count of the number of ajax requests). We also have a method on the bean, update (line 6), which will be called every time the ajax call is submitted.

The behavior of this page is pretty simple - every time you press a character in the inputText, the complete value of the input is echoed to the outputText "out" (line 1) - the length of "out" is written to "count" (line 3), and the "eventCount" outputText (line 9) has it’s value incremented by one.

So - what code is in the bean? Here’s the relevant bits:

   1 public void setHello(String hello) {
   2     this.hello = hello;
   3 }
   4 public int getCount() {
   5     return count;
   6 }
   7 public int getEventCount() {
   8     return eventCount;
   9 }
  10 public void update(AjaxBehaviorEvent event) {
  11     count = hello.length();
  12     eventCount++;
  13 }

Not so bad - the only thing new here is that AjaxBehaviorEvent class - and we’re not even using it. The update method will simply set up the values to be correct, and we let the Ajax render to the rest. So - listeners are easy.

Facelets Components

Now, we’ll want to create a custom tag in Java. To do that, we’ll need to make a few configuration file entries, and write a little java code. But first, let’s see it used in the page:

In the XHTML header, we’ll say:

   1 <html xmlns="http://www.w3.org/1999/xhtml"
   2       xmlns:ui="http://java.sun.com/jsf/facelets"
   3       xmlns:h="http://java.sun.com/jsf/html"
   4       xmlns:f="http://java.sun.com/jsf/core"
   5       xmlns:cu="http://javaserverfaces.dev.java.net/demo/custom-taglib">

Setting up the "cu" prefix (line 5) to point to "custom-taglib" (the whole URL is significant). Then later on in the page, we’ll use it like so:

<cu:custom id="customId">

We then need to add an entry in web.xml:

   1 <context-param>
   2    <param-name>javax.faces.FACELETS_LIBRARIES</param-name>
   3    <param-value>/WEB-INF/custom-taglib.xml</param-value>
   4 </context-param>

This points to our next config file, which is the filename on line 3. Here’s its contents, in full:

   1 <facelet-taglib xmlns="http://java.sun.com/xml/ns/javaee"
   2               xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   3               xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-facelettaglibrary_2_0.xsd"
   4               version="2.0">
   5   <namespace>http://javaserverfaces.dev.java.net/demo/custom-taglib</namespace>
   6   <tag>
   7     <tag-name>custom</tag-name>
   8       <component>
   9         <component-type>mycustom</component-type>
  10       </component>
  11   </tag>
  12 </facelet-taglib>

Note that the namespace element on line 5 matches the URL we used for the namespace in the html element of the using page. We said this taglibrary will have one tag "custom" (line 7), which maps to the FacesComponent "mycustom". Where does it find the definition of "mycustom"? In the Java file defining the component, using the new @FacesComponent attribute. Here’s the full Java code, leaving out the imports:

   1 @FacesComponent(value = "mycustom")
   2 public class MyCustom extends UIComponentBase {
   3
   4     @Override
   5     public String getFamily() {
   6         return "custom";
   7     }
   8
   9     @Override
  10     public void encodeEnd(FacesContext context) throws IOException {
  11
  12         ResponseWriter responseWriter = context.getResponseWriter();
  13         responseWriter.startElement("div", null);
  14         responseWriter.writeAttribute("id",getClientId(context),"id");
  15         responseWriter.writeAttribute("name", getClientId(context),"clientId");
  16         responseWriter.write("Howdy!");
  17         responseWriter.endElement("div");
  18     }
  19 }

In fact, the Java code itself is simple enough that I don’t really think it requires any explanation. Putting the cu:custom tag in your page will now render Howdy!, surrounded by a div with the same id and name as you gave the component. All that’s left is to add the Ajax. That… is a bit more complicated, but now that we’ve handled everything else, it’s really just incremental.

Using f:ajax with your custom tag

To use the f:ajax tag, we’d like to, for instance, do something like this:

   1 <cu:custom id="customId">
   2     <f:ajax render="eventcount" listener="#{custom.updateEventCount}"/>
   3 </cu:custom>

Meaning, we’d like to just decorate the tag, and let it do something "smart". In this case, we’ll default to "onclick" (since we’re dealing with a div, after all, we could also default to "onmouseover", for instance). It’d also be nice if we could still call the ajax listener. That’ll require a bit more code. Here’s the full Java component, with the additional ajax code. I’ll go over it at the end:

   1 @FacesComponent(value = "mycustom")
   2 public class MyCustom extends UIComponentBase implements ClientBehaviorHolder {
   3
   4     @Override
   5     public String getFamily() {
   6         return "custom";
   7     }
   8
   9     @Override
  10     public void encodeEnd(FacesContext context) throws IOException {
  11
  12         ClientBehaviorContext behaviorContext =
  13                 ClientBehaviorContext.createClientBehaviorContext(context,
  14                 this, "click", getClientId(context), null);
  15
  16         ResponseWriter responseWriter = context.getResponseWriter();
  17         responseWriter.startElement("div", null);
  18         responseWriter.writeAttribute("id",getClientId(context),"id");
  19         responseWriter.writeAttribute("name", getClientId(context),"clientId");
  20         Map<String,List<ClientBehavior>> behaviors = getClientBehaviors();
  21         if (behaviors.containsKey("click") ) {
  22             String click = behaviors.get("click").get(0).getScript(behaviorContext);
  23             responseWriter.writeAttribute("onclick", click, null);
  24         }
  25         responseWriter.write("Click me!");
  26         responseWriter.endElement("div");
  27     }
  28
  29
  30     @Override
  31     public void decode(FacesContext context) {
  32         Map<String, List<ClientBehavior>> behaviors = getClientBehaviors();
  33         if (behaviors.isEmpty()) {
  34             return;
  35         }
  36
  37         ExternalContext external = context.getExternalContext();
  38         Map<String, String> params = external.getRequestParameterMap();
  39         String behaviorEvent = params.get("javax.faces.behavior.event");
  40
  41         if (behaviorEvent != null) {
  42             List<ClientBehavior> behaviorsForEvent = behaviors.get(behaviorEvent);
  43
  44             if (behaviors.size() > 0) {
  45                 String behaviorSource = params.get("javax.faces.source");
  46                String clientId = getClientId(context);
  47                if (behaviorSource != null && behaviorSource.equals(clientId)) {
  48                    for (ClientBehavior behavior: behaviorsForEvent) {
  49                        behavior.decode(context, this);
  50                    }
  51                }
  52             }
  53         }
  54     }
  55
  56     @Override
  57     public Collection<String> getEventNames() {
  58         return Arrays.asList("click");
  59     }
  60
  61     @Override
  62     public String getDefaultEventName() {
  63         return "click";
  64     }
  65 }

At 65 lines, this is probably the longest code example I’ve ever posted, but most of this is either really easy, or stuff you’ve seen in the previous section. First, we define what Ajax events we’ll accept ("click") and what one is the default ("click" again), on lines 56-64. These are part of the ClientBehaviorHolder interface (line 2). We also had to add a little code to the encodeEnd method, so that we correctly output the DOM event script as part of the div (lines 12-14, 20-24). And lastly, we needed to add a decode method, since our component is no longer output only - the ajax event handling code is always part of the decode process (lines 31-50). This is the part where we actually make sure that that listener is being called.

Did I mention that you can do pretty much the same thing in a composite component? That’ll be the subject of a future blog.

Well, I warned you this was a little more complex - hopefully it’s all fairly clear. If it isn’t - ask in the comments.

It’s been a while since I posted any news JavaFX plug-in for Eclipse, but we’ve been working hard on the following new features: Code assist for syntax keywords, Code assist for system classes, Code assist for attributes of system classes, Code assist for user classes, Code assist for attributes of user classes.
Syntax highlight

A new version will be released in the […]

On2 Technologies announced that it has released its new flagship hardware video decoder design, the Hantro(TM) 9190. The 9190 is the tenth generation of the Hantro line of decoders, which are deployed in hundreds of millions of chips worldwide. The 9190 design supports video playback up to full HD (1080p) resolution at 60 frames per second (fps) in multiple formats including On2 VP6 for Adobe Flash Player and Sun JavaFX, DivX 3, 4, 5, 6, H.264, H.263, Sorenson Spark, MPEG-1, MPEG-2, MPEG-4, VC-1/WMV9 and RealVideo 8, 9 & 10, as well as up to 66 megapixel JPEG still images.

October 2009

July 2009 New Java Performance Tips

GM Canada September 2009 Sales Results

The Case for Single-Purpose Services

JSF 2, Custom Java Components, and AJAX Behaviors

First, the Ajax Listener

Facelets Components

Using f:ajax with your custom tag

New Version of Exadel Studio JavaFX Plug-in Is Coming…

On2 Technologies Releases First VP6 Hardware Video Decoder

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