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Java Unit 5: Applets and Graphics
Putting Applets into Web Pages
Two things are involved in the process of putting applets onto web pages◦ The .class files of the applet◦ The html file of the page
Remember: any Java source file that compiles correctly will produce a .class file.
Classes and HTMLs.
Compiled .class files for Java source code should be found:◦ C:/UserName/workspace/NameOfProject/bin
It may also be found in◦ C:/UserName/Android/workspace/NameOfProject/
bin
Finding the .class files
The HTML file should be created inside the same folder as the .class files for the applet.◦ This is to reduce complexity in defining the path
to the applet class in the HTML file. You could start creating an HTML file in
Notepad by:◦ Starting a new text file, and adding your code
from there◦ When it comes time to save, remove the *.txt
extension, and add ‘.html’ to the end of the file instead. (Ex: MyHtmlPage.html)
Creating the HTML
<html><applet code=“MyJavaApplet.class” width=“500” height=“500”></applet></html>
HTML Code
HTML is a markup language, using a system of tags to define elements of a document.
<html> is a tag that denotes a start of an html file, while </html> denotes the end.
Likewise, <applet> and </applet> are used in the same way.
HTML Code
You’ll notice inside the first applet tag, there are attributes assigned inside it (code, width, height)◦ ‘code’ is the directory where the HTML file would
be able to find the main .class entry point for the applet.
◦ ‘width’ and ‘height’ define the size as it appears on the web page.
◦ Note that the values assigned to these attributes are defined in double quotes.
HTML Code
If you have to change a line in the source code of the Java files and recompile, you should replace the .class file in the html directory with the new one.
When running Java applets, the user must have the Java Runtime Environment installed.
For security or other reasons, some systems may not run Java content through web pages.
A couple of other notes
With the newest version of Java, unsigned applets are not allowed to run on any machine.
This means that if we try running our applet through an html page we created, the applet will not run at all, because it is considered a security risk.
Therefore, we’ll need to create an exception for this.
Passing Security
Open the Java Control Panel◦ On Windows start, search for “Configure Java”◦ Java\jre7\bin\javacpl.exe
Go to the Security tab, and click the “Edit Site List…” button.
In the blank space on the dialog, type in the file or html location of the html file you want to run.◦ Ex: http://math.uaa.alaska.edu/~android/
java/unit5/unit5applet Click Add, then OK on both dialogs. You should
be able to run that applet now.
Passing Security
