A Closer Look at Simple Components in Apache Tapestry - Form component (Page 2 of 4 )
To define this component in the Home page template, simply mark the existing HTML form with a jwcid attribute and give the component a descriptive name, like so:
<form action="" jwcid="secretWordForm">
The next step is to configure the Form component in page specification:
<component id="secretWordForm" type="Form">
<binding name="listener" value="listener:onWordSubmit"/>
</component>
Let’s concentrate on the <binding> element as everything else should be clear for you now.
The name=”listener” attribute says that what we are specifying in this binding is a listener. Listener can be understood as a special method of the page class, which is invoked when an event associated with this listener happens. Here the event is the form submission.
The value="listener:onWordSubmit" attribute provides the name for the listener method. Note the ‘listener’ prefix. You are already familiar with two prefixes, ‘ognl’ and ‘literal’, so here is the third one for your collection. It is used to tell Tapestry that what follows is not an OGNL expression and not a literal value, it is rather the name for the listener method to be invoked when the form is submitted.
All that is left is to provide the listener method in the Home page class. There are a few ways in which a listener can be written, but again, let me delay the complete explanation until the next article. Right now, we shall create a very simple listener like this:
public String onWordSubmit() {
return "Secret";
}
This is an ordinary public method, and its only “special feature” is that it returns a String containing the name of the next page to show. Normally, before returning this name we would do something, say, manipulate some data, but for now let’s just leave everything very simple.
We can already run the new application and see how it works. Hit the F6 key, and NetBeans will compile, package and deploy everything for you. The Home page will appear, looking exactly like its mock up, but if you try to enter a word into the text box, it will be masked, like a password. Finally, press the Submit button, and you will see the Secret page – i.e. its mockup with both views shown as we didn’t add any functionality for that page yet.
Phew… I feel like this article is becoming too lengthy, and there are still a lot of things to discuss and play with. [In fact, we had to break it into two parts. --Ed.] Let me take a break here and continue the general discussion in the next article.
Next: Source Code >>
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