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Listing 4. The Java code for the weblet class
import org.w3c.dom.*;
import org.w3c.dom.html.*;
import org.w3c.dom.events.*;
import com.ibm.weblet.*;
import java.net.*;
public class ConversationDemo implements Weblet
{
private WebletContext m_engine;
private HTMLDocument doc;
private HTMLElement HeadingSection;
private HTMLElement FormSection;
private HTMLElement ControlsSection;
private HTMLFormElement PersonalInformationForm;
private HTMLFormElement AddressInformationForm;
private ControlsEventListener LocalEventHandler = new ControlsEventListener();
private int ProcessingStep = 0;
private HTMLButtonElement RetreatButton;
private HTMLButtonElement ContinueButton;
private Node BreakingSpace;
/** Creates new ConversationDemo */
public ConversationDemo()
{
}
/**
* Called when the Weblet is first loaded into memory.
*/
public void init(WebletContext engine)
{
try
{
Element GenericElement;
m_engine = engine;
doc = m_engine.getOwnerDocument();
BreakingSpace = doc.createTextNode(" ");
GenericElement = doc.getElementById("HeadingSection");
if(GenericElement instanceof HTMLElement)
HeadingSection = (HTMLElement)GenericElement;
else
throw(new NotImplementedException());
GenericElement = doc.getElementById("FormSection");
if(GenericElement instanceof HTMLElement)
FormSection = (HTMLElement)GenericElement;
else
throw(new NotImplementedException());
GenericElement = doc.getElementById("ControlsSection");
if(GenericElement instanceof HTMLElement)
ControlsSection = (HTMLElement)GenericElement;
else
throw(new NotImplementedException());
GenericElement = doc.getElementById("PersonalInformationForm");
if(GenericElement instanceof HTMLFormElement)
PersonalInformationForm = (HTMLFormElement)GenericElement;
else
throw(new NotImplementedException());
GenericElement = doc.getElementById("AddressInformationForm");
if(GenericElement instanceof HTMLFormElement)
AddressInformationForm = (HTMLFormElement)GenericElement;
else
throw(new NotImplementedException());
GenericElement = doc.getElementById("ContinueButton");
if(GenericElement instanceof HTMLButtonElement)
ContinueButton = (HTMLButtonElement)GenericElement;
else
throw(new NotImplementedException());
GenericElement = doc.getElementById("RetreatButton");
if(GenericElement instanceof HTMLButtonElement)
RetreatButton = (HTMLButtonElement)GenericElement;
else
throw(new NotImplementedException());
} catch (ComException ComEx)
{
String exName = ComEx.getClass().getName();
m_engine.showDialog("Fatal exception in Weblets Plugin in init()", exName);
} catch (NotImplementedException NotImpEx)
{
Transcript.println("Source HTML page is missing required elements in init()");
Transcript.printStackTrace(NotImpEx);
Transcript.showTranscript(true);
} catch (DOMException DOMEx)
{
Transcript.println("Failure accessing DOM tree in init()");
Transcript.printStackTrace(DOMEx);
Transcript.showTranscript(true);
} catch (org.w3c.dom.events.EventException EventEx)
{
Transcript.println("Failure accessing DOM events in init()");
Transcript.printStackTrace(EventEx);
Transcript.showTranscript(true);
}
catch(Exception e)
{
Transcript.println("Other Exception in init()");
Transcript.printStackTrace(e);
Transcript.showTranscript(true);
}
}
/**
* Called after the Weblet is setup and ready to go. This is called each time
* the browser refreshes the page or returns to the page.
*/
public void start()
{
// Note: there are four exception types that any DOM or weblet call could raise.
// these are caught by this try/catch block. The ComException and NotImplementedException
// are both Runtime Exceptions, so they could have been ignored, although that is not
// good practice.
try
{
ControlsSection.removeChild(RetreatButton);
FormSection.removeChild(PersonalInformationForm);
FormSection.removeChild(AddressInformationForm);
addTextIntroduction();
((EventTarget)ContinueButton).addEventListener("click", LocalEventHandler, false);
((EventTarget)RetreatButton).addEventListener("click", LocalEventHandler, false);
} catch (ComException ComEx)
{
String exName = ComEx.getClass().getName();
m_engine.showDialog("Fatal exception in Weblets Plugin in start()", exName);
} catch (NotImplementedException NotImpEx)
{
Transcript.println("Method not implemented in this version of DirectDOM(tm) in start()");
Transcript.printStackTrace(NotImpEx);
Transcript.showTranscript(true);
} catch (DOMException DOMEx)
{
Transcript.println("Failure accessing DOM tree in start()");
Transcript.printStackTrace(DOMEx);
Transcript.showTranscript(true);
} catch (org.w3c.dom.events.EventException EventEx)
{
Transcript.println("Failure accessing DOM events in start()");
Transcript.printStackTrace(EventEx);
Transcript.showTranscript(true);
}
}
/**
* Called just before the browser leaves the page the Weblet is on.
*/
public void stop()
{
((EventTarget)RetreatButton).removeEventListener("click", LocalEventHandler, false);
((EventTarget)ContinueButton).removeEventListener("click", LocalEventHandler, false);
}
/**
* Called just before the Weblet is removed from memory.
*/
public void destroy()
{
}
protected void addTextIntroduction()
{
StringBuffer IntroParagraphText = new StringBuffer();
IntroParagraphText.append("This evening we will be working through");
IntroParagraphText.append(" a demonstration weblet together. ");
IntroParagraphText.append("This weblet works with a servlet on the");
IntroParagraphText.append(" server to provide a more responsive ");
IntroParagraphText.append("user interface, and to permit data to be");
IntroParagraphText.append(" transferred without the usual ");
IntroParagraphText.append("limitations of browser-based communications.");
try
{
Element TitleParagraph = doc.createElement("P");
TitleParagraph.appendChild(
doc.createTextNode("Welcome to the Weblets Conversation Demonstration."));
Element HeadingElement = doc.createElement("H1");
HeadingElement.appendChild(TitleParagraph);
HeadingElement.appendChild(doc.createElement("/P"));
Element IntroParagraph = doc.createElement("P");
IntroParagraph.appendChild(doc.createTextNode(IntroParagraphText.toString()));
Element CenterElement = doc.createElement("Center");
CenterElement.appendChild(HeadingElement);
CenterElement.appendChild(doc.createElement("/H1"));
HeadingSection.appendChild(CenterElement);
HeadingSection.appendChild(doc.createElement("/Center"));
HeadingSection.appendChild(IntroParagraph);
HeadingSection.appendChild(doc.createElement("/P"));
} catch (DOMException DOMEx)
{
Transcript.println("Failure accessing DOM tree in start()");
Transcript.printStackTrace(DOMEx);
Transcript.showTranscript(true);
} catch (org.w3c.dom.events.EventException EventEx)
{
Transcript.println("Failure accessing DOM events in start()");
Transcript.printStackTrace(EventEx);
Transcript.showTranscript(true);
}
}
private boolean validatePersonalForm()
{
return true;
}
private boolean validateAddressForm()
{
return true;
}
private class ControlsEventListener implements EventListener
{
public void handleEvent(Event ControlEvent)
{
boolean GoForward;
try
{
GoForward = (((HTMLButtonElement)
(ControlEvent.getTarget())).getName().equalsIgnoreCase("ContinueButton"));
switch(ProcessingStep)
{
case 0:
if(GoForward == true)
{
FormSection.appendChild(PersonalInformationForm);
ControlsSection.appendChild(RetreatButton);
ControlsSection.appendChild(BreakingSpace);
ControlsSection.appendChild(ContinueButton);
ContinueButton.setValue("Next");
RetreatButton.setValue("Previous");
ProcessingStep = 1;
}
else
{
}
break;
case 1:
if(GoForward)
{
if(validatePersonalForm());
{
FormSection.removeChild(PersonalInformationForm);
FormSection.appendChild(AddressInformationForm);
ContinueButton.setValue("Submit");
ProcessingStep = 2;
}
}
else
{
FormSection.removeChild(PersonalInformationForm);
ControlsSection.removeChild(RetreatButton);
ContinueButton.setValue("Continue");
ProcessingStep = 0;
}
break;
case 2:
if(GoForward)
{
if(validateAddressForm())
{
// add code here to submit the form data.
// a thought: have another from with nothing but hidden
// fields for the required data and a have the browser
// submit that form.
}
}
else
{
FormSection.removeChild(AddressInformationForm);
FormSection.appendChild(PersonalInformationForm);
ControlsSection.appendChild(RetreatButton);
ControlsSection.appendChild(BreakingSpace);
ControlsSection.appendChild(ContinueButton);
RetreatButton.setValue("Previous");
ContinueButton.setValue("Next");
ProcessingStep = 1;
}
break;
}
Runtime.getRuntime().gc();
} catch (ComException ComEx)
{
String exName = ComEx.getClass().getName();
m_engine.showDialog("Fatal exception in Weblets Plugin in handleEvent()", exName);
} catch (NotImplementedException NotImpEx)
{
Transcript.println("Method not implemented in this version" +
" of DirectDOM(tm) in handleEvent()");
Transcript.printStackTrace(NotImpEx);
Transcript.showTranscript(true);
} catch (DOMException DOMEx)
{
Transcript.println("Failure accessing DOM tree in handleEvent()");
Transcript.printStackTrace(DOMEx);
Transcript.showTranscript(true);
} catch (org.w3c.dom.events.EventException EventEx)
{
Transcript.println("Failure accessing DOM events in handleEvent()");
Transcript.printStackTrace(EventEx);
Transcript.showTranscript(true);
}
catch(Exception e)
{
Transcript.println("Other Exception in handleEvent()");
Transcript.printStackTrace(e);
Transcript.showTranscript(true);
}
}
}
}
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