edu.utexas.beg.agi.servlet
Class DynamicHTMLPage

java.lang.Object
  |
  +--edu.utexas.beg.agi.servlet.DynamicHTMLPage

Direct Known Subclasses:

PostStep1Page, PostStep2Page, Step1Page, Step2Page, Step3Page

public abstract class DynamicHTMLPage

extends Object

Abstract parent class of Objects representing HTML pages with dynamic content.

This class provides a default implementation of the streamPage() method, which is the main function of DynamicHTMLPages. The default implementation streams a static .prefix file, calls the streamDynamicContent() method, and then streams a static .suffix file. Subclasses can over-ride the streamDynamicContent() method to generate HTML code that includes, for example, values from the current UserParameters.

The AGIServlet has a List of DynamicHTMLPages which is established in its createDynamicHTMLPages() method. When a page is requested, the Servlet searches these page Objects to find one that canHandlePage(), and then calls its streamPage() method. Generally, each subclass of DynamicHTMLPage will represent one page file, such as step1.html.

Example: Suppose there is class Step1Page, which extends DynamicHTMLPage.

The class passes "step1.html" as its filePath during construction, and it overrides the streamDynamicContent() method to generate an HTML form.
The static part of the HTML page (everything before the generated HTML) is created and placed in a file called /home/httpd/servlet/html/step1.html.prefix. Everything after the generated HTML is placed in a file called /home/httpd/servlet/html/step1.html.suffix.
An instance of this class is created and installed in the createDynamicHTMLPages() method of the AGIServlet.
At run-time, when a request for page "step1.html" is received, the AGIServlet searches it's DynamicHTMLPages, finding that this (Step1Page) Object can handle the request. The Servlet then calls its streamPage() method. The default implementation of that method streams the step1.html.prefix file, then calls the streamDynamicContent() method which generates the HTML form. Finally, the step1.html.suffix file is streamed back to the client browser.

See Also:

AGIServlet.createDynamicHTMLPages()

Field Summary

private String	filePath The relative path of the URL that this page will support.
private File	rootFilePath The root of all file paths, i.e.

Constructor Summary

DynamicHTMLPage(String filePath)
Creates a dynamic HTML page for handling the given file path.

Method Summary

boolean	canHandlePage(String filePath) Determines if the given file path can be serviced by this Object.
protected abstract void	streamDynamicContent(String page, UserParameters parameters, PrintWriter outStream) Streams the actual dynamic content for this page.
void	streamPage(String page, UserParameters parameters, PrintWriter outStream) Streams HTML content to the client browser.

Methods inherited from class java.lang.Object

, clone, equals, finalize, getClass, hashCode, notify, notifyAll, registerNatives, toString, wait, wait, wait

Field Detail

rootFilePath

private File rootFilePath

The root of all file paths, i.e. /home/httpd/servlet/html/. In particular, .prefix and .suffix files used by this class are found within this root directory.

filePath

private String filePath

The relative path of the URL that this page will support. For example, if this value is mod1/index.html, then requests for that page will be handled by this Object. If this parameter is null then the canHandlePage() method must be over-ridden to properly handle pages.

Constructor Detail

DynamicHTMLPage

public DynamicHTMLPage(String filePath)

Creates a dynamic HTML page for handling the given file path.

Parameters:

filePath - the relative path of the URL that this page will support. For example, if this value is mod1/index.html, then requests for that page will be handled by this Object. If this parameter is null then the canHandlePage() method must be over-ridden to properly handle pages.

Method Detail

canHandlePage

public boolean canHandlePage(String filePath)

Determines if the given file path can be serviced by this Object.

If a filePath was given when this Object was constructed, then it is matched to the given path. If no filePath was used, then subclasses must provide an implementation of this method, or it will always return false.

streamPage

public void streamPage(String page,
                       UserParameters parameters,
                       PrintWriter outStream)
                throws IOException

Streams HTML content to the client browser.

This method looks for a page.prefix and a page.suffix file. If a prefix file exists, then it is streamed statically. Then the streamDynamicContent() method is called to stream the actual dynamic part of the page. Then the suffix file is streamed statically, if it exists.

Subclasses probably will not need to implement this method. They can over-ride the streamDynamicContent() method, and create static .prefix and .suffix files if desired.

Parameters:

page - the relative file path of the page to stream.

parameters - the current parameter values set by the human user.

outStream - the output stream to write the HTML content to. This stream returns data to the client browser.

streamDynamicContent

protected abstract void streamDynamicContent(String page,
                                             UserParameters parameters,
                                             PrintWriter outStream)
                                      throws IOException

Streams the actual dynamic content for this page.

Parameters:

page - the relative file path of the page to stream.

parameters - the current parameter values set by the human user.

outStream - the output stream to write the HTML content to. This stream returns data to the client browser.