Thursday Dec 05, 2013

Current Date / Time on your JSF pages

OK, it's a trivial problem but I'll answer to anyway. Is there a simple way to get the date and time in expression language inside your pages, without writing Java code?

The answer is of course yes, it's simple to do in a declarative manner.  You will need to create a basic managed bean definition in your JSF configuration.  So for example I might add the following definition for a bean called "now" to my adfc-config.xml file:

  <managed-bean>
    <managed-bean-name>now</managed-bean-name>
    <managed-bean-class>java.util.Date</managed-bean-class>
    <managed-bean-scope>request</managed-bean-scope>
  </managed-bean> 

That's enough to ensure that a Date object called "now" is available on the request map and is re-created (i.e. refreshed) on every roundtrip.  This can then be referenced inside of your page:

  <af:outputText value="#{now}">
    <af:convertDateTime type="both" timeZone="CET"/>
  </af:outputText> 

Notice how I've specified the timezone I want to see here as the result of the new Date() creation will be the date in UTC / GMT.

There you are, short and sweet. 

Thursday Apr 05, 2012

Application Scope v's Static - Not Quite the same

An interesting question came up today which, innocent as it sounded, needed a second or two to consider. What's the difference between storing say a Map of reference information as a Static as opposed to storing the same map as an application scoped variable in JSF? 

From the perspective of the web application itself there seems to be no functional difference, in both cases, the information is confined to the current JVM and potentially visible to your app code (note that Application Scope is not magically propagated across a cluster, you would need a separate instance on each VM).

To my mind the primary consideration here is a matter of leakage. A static will be (potentially) visible to everything running within the same VM (OK this depends on which class-loader was used but let's keep this simple), and this includes your model code and indeed other web applications running in the same container. An Application Scoped object, in JSF terms, is much more ring-fenced and is only visible to the Web app itself, not other web apps running on the same server and not directly to the business model layer if that is running in the same VM.

So given that I'm a big fan of coding applications to say what I mean, then using Application Scope appeals because it explicitly states how I expect the data to be used and a provides a more explicit statement about visibility and indeed dependency as I'd generally explicitly inject it where it is needed. 

Alternative viewpoints / thoughts are, as ever, welcomed...

Saturday May 08, 2010

Script For Detecting Availability of XMLHttp in Internet Explorer

Having the XMLHttpRequest API available is key to any ADF Faces Rich Client application. Unfortunately, it is possible for users to switch off this option in Internet Explorer as a Security setting. Without XMLHttpRequest available, your ADF Faces application will simply not work correctly, but rather than giving the user a bad user experience wouldn't it be nicer to tell them that they need to make some changes in order to use the application? 
Thanks to Blake Sullivan in the ADF Faces team we now have a little script that can do just this.
The script is available from the sample code page here, just look for the browserCheck.js sample - This is what you'll need to add to your project.
The best way to use this script is to make changes to whatever template you are using for the entry points to your application. If you're not currently using template then you'll have to make the same change in each of your JSPX pages.
  1. Save the browserCheck.js file into a /js/ directory under your HTML root within your UI project (e.g. ViewController)
  2. In the template or page, select the <af:document> object in the Structure window.
  3. From the right mouse (context) menu choose Facet and select the metaContainer facet.
  4. Switch to the source code view and locate the metaContainer facet. Then insert the following lines (I've included the facet tag for clarity but you'll already have that):
      <f:facet name="metaContainer">
        <af:resource type="javascript"
                     source="/js/browserCheck.js"/>
        <af:resource type="javascript">
           xmlhttpNativeCheck(
                     "help/howToConfigureYourBrowser.html");
        </af:resource>
      </f:facet>

Note that the argument to the xmlhttpNativeCheck function is a page that you want to show to the user if they need to change their browser configuration. So build this page in the appropriate place as well. You can also just call the function without any arguments e.g. xmlhttpNativeCheck(); in which case it will pop up default instructions for the user to follow, but not redirect to any other page.
About

Hawaii, Yes! Duncan has been around Oracle technology way too long but occasionally has interesting things to say. He works in the Development Tools Division at Oracle, but you guessed that right? In his spare time he contributes to the Hudson CI Server Project at Eclipse
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Note that comments on this blog are moderated so (1) There may be a delay before it gets published (2) I reserve the right to ignore silly questions and comment spam is not tolerated - it gets deleted so don't even bother, we all have better things to do with our lives.
However, don't be put off, I want to hear what you have to say!

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