Applet_01

"Properties" are Java's (platform-independent) equivalent to "environment variables". "Applet_01" looks for predefined "system properties" and finds out which of them are accessible from within an applet.

Please, also consider my "Hints for Reading" and the "List of Recent Changes"!

The applet on the left side shows a list of property_name=property_value pairs. Some properties are "(unavailable)" which means that these items don't exist, others are "(inaccessible)" which means that they cannot be accessed from within an applet. The actual contents may depend on whether an appletviewer or a web browser is used to execute the applet.

System Properties

When started, a java interpreter (or web browser) predefines a set of "standard system properties" which can then be examined from within an applet or an application. While applications may create new properties and modify existing ones, applets have only limited access.

A typical output (produced by an applet running inside an appletviewer) might look as follows:

• java.version = "1.0.2"
• java.vendor = "Sun Microsystems Inc."
• java.vendor.url = "http://www.sun.com"
• java.home = "c:\Programme\Java\bin\.."
• java.class.version = "45.3"
• java.class.path = ".;c:\Programme\Java\lib\classes.zip"
• os.name = "Windows 95"
• os.arch = "x86"
• os.version = "4.0"
• file.separator = "\"
• path.separator = ";"
• line.separator = "\n"
• user.name = "Rozek"
• user.home = "c:\Programme\Java"
• user.dir = "c:\Rozek\Java\Applets\Applet_01"
• awt.toolkit = "sun.awt.win32.MToolkit"
• awt.appletWarning = (unavailable)
• acl.read = "+"
• acl.read.default = ""
• acl.write = "+"
• acl.write.default = ""
• appletviewer.security.model = (unavailable)
• firewallHost = "sunweb.ebay"
• firewallPort = "80"
• firewallSet = "true"
• package.restrict.access.java = (unavailable)
• package.restrict.access.sun = "true"
• package.restrict.definition.java = "true"
• package.restrict.definition.sun = "true"
• proxyHost = (unavailable)
• proxyPort = (unavailable)
• proxySet = (unavailable)

Unfortunately, an applet is not allowed to create a list of available system properties using the getProperties method - the SecurityManager prohibits this call. As a consequence, the "standard" set had to be explicitly coded into "Applet_01".

Source Code

The source code of this applet is available for download:

• Applet_01.java (ASCII file, 13711 bytes)