19.9 Java4655: a rendering web browser

Table of contents

• Preface
  • Viewing tip
    • Figures
    • Listings
• Discussion and sample code
  • A skeleton program - Java4655c
  • The program named Java4655b
  • The program named Java4655a
  • What's missing?
• Run the program
• What's next?
• Miscellaneous
• Complete program listing

Preface

This module is one in a collection of modules designed for teaching INEW 2338 Advanced Java (Web) at Austin Community College in Austin, TX. More specifically, it is one in asub-collection of modules designed for teaching network programming in that course. The purpose of this module is to show students how to use Java Swingto render a web page in a JFrame object.

Viewing tip

I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the Figuresand Listings while you are reading about them.

Figures

• Figure 1 . JFrame output from the program named Java4655c.
• Figure 2 . Command line output from the program named Java4655c.
• Figure 3 . JFrame output from the program named Java4655b.
• Figure 4 . JFrame output from the program named Java4655a.

Listings

• Listing 1 . Beginning of the program named Java4655c.
• Listing 2 . The method named runner.
• Listing 3 . Beginning of the class named Java4655cHtmlHandler.
• Listing 4 . Open the URL object in a JEditorPane object.
• Listing 5 . Register a hyperlink listener.
• Listing 6 . Display the JEditorPane.
• Listing 7 . The hyperlinkUpdate method.
• Listing 8 . The constructor for the Java4655bHtmlHandler class.
• Listing 9 . The HyperlinkEvent handler for Java4655b.
• Listing 10 . Scrolling code in Java4655a.
• Listing 11 . The program named Java4655c.
• Listing 12 . The program named Java4655b.
• Listing 13 . The program named Java4655a.

Discussion and sample code

In an earlier module, you learned how to connect to a website and cause a raw text version of a file to be downloaded and displayed. However, the display of raw HTMLtext isn't very useful, which is why rendering web browsers were invented.

In this module, you will learn how to connect to a website and cause an HTML file to be downloaded and rendered in a JFrame object. We will develop a program that makes it possible to follow hyperlinks much as you wouldexpect with a commercial web browser.

A skeleton program - Java4655c

I will begin this explanation with a skeleton program that illustrates four important aspects of rendering a webpage in a Swing JFrame object :

• Getting a URL object that is connected to a webpage.
• Opening the URL object in a JEditorPane object.
• Displaying the JEditorPane in a rendered format.
• Handling hyperlink events on the JEditorPane .

(Note that there are alternatives to the first two items in the above list, which we will see later.)

To keep the code simple, two important aspects of webpage rendering will be omitted from this program:

• Scrolling large web pages.
• Following hyperlinks.

These capabilities will be added to other programs later in this module.

Beginning of the program named Java4655c