The APPLET Tag






Documentation Contents






The APPLET Tag









Here is an example of a simple APPLET tag:

<applet code="MyApplet.class" width=100 height=140></applet>

This tells the viewer or browser to load the applet whose compiled
code is in MyApplet.class (in the same directory as the current HTML
document), and to set the initial size of the applet to 100 pixels
wide and 140 pixels high.

Here's a more complex example of an APPLET tag:

<applet codebase="http://java.sun.com/applets/NervousText/1.1"
code="NervousText.class" width=400 height=75>
<param name="text" value="Welcome to HotJava!">
<hr>
If you were using a Java-enabled browser such as HotJava,
you would see dancing text instead of this paragraph.
<hr>
</applet>

This tells the viewer or browser to load the applet whose compiled
code is at the URL
http://java.sun.com/applets/NervousText/1.1/NervousText.class,
to set the initial size of the applet to 400x75 pixels.
The viewer/browser must also
set the applet's "text" attribute (which customizes the text this
applet displays) to be "Welcome to HotJava!" If the page is
viewed by a browser that can't execute Java applets, then the browser
will ignore the APPLET and PARAM tags, displaying only the HTML between
the <param> and </applet> tags
(the alternate HTML).

Here's the result of putting the above example in your HTML file.
(The first time you load this page, you may have to wait for the applet
to be loaded.)




If you were using a Java-enabled browser such as HotJava,
you would see dancing text instead of this paragraph.



Here is another example of an APPLET tag:

<applet code=A21 width=256 height=256 archive="toir.jar">
<param name=img value=test.gif>
<hr>
We need to convert some of the standard applets to use
archive. Any volunteers?
<hr>
</applet>

In this example, the applet class is A21. Its bytecodes
(may) reside in the archive "toir.jar". This archive may
also contain the image resource (see resources documentation)
with name test.gif.

Here's the complete syntax for the APPLET tag. Required elements are in
bold. Optional elements are in regular typeface. Elements
your specify are in italics.

<APPLET
CODEBASE = codebaseURL
ARCHIVE = archiveList
CODE = appletFile ...or... OBJECT = serializedApplet
ALT = alternateText
NAME = appletInstanceName
WIDTH = pixels HEIGHT = pixels
ALIGN = alignment
VSPACE = pixels HSPACE = pixels
>
<PARAM NAME = appletAttribute1 VALUE = value>
<PARAM NAME = appletAttribute2 VALUE = value>
. . .
alternateHTML
</APPLET>


CODE, CODEBASE, and so on are attributes of the applet tag; they give
the browser information about the applet. The only mandatory
attributes are CODE, WIDTH, and HEIGHT. Each attribute is described
below.


CODEBASE = codebaseURL

This OPTIONAL attribute specifies the base URL of the applet--the
directory that contains the applet's code. If this attribute
is not specified, then the document's URL is used.

ARCHIVE = archiveList

This OPTIONAL attribute describes one or more archives containing
classes and other resources that will be "preloaded". The
classes are loaded using an instance of an AppletClassLoader
with the given CODEBASE.

The archives in archiveList are separated by ",".
NB: in JDK1.1, multiple APPLET tags with the same CODEBASE share
the same instance of a ClassLoader. This is used by some client
code to implement inter-applet communication. Future JDKs may
provide other mechanisms for inter-applet communication.
For security reasons, the applet's class loader can read only
from the same codebase from which the applet was started. This
means that archives in archiveList must be in the same
directory as, or in a subdirectory of, the codebase. Entries in
archiveList of the form ../a/b.jar will not work
unless explicitly allowed for in the security policy file (except
in the case of an http codebase, where archives in archiveList
must be from the same host as the codebase, but can have
".."'s in their paths.)

CODE = appletFile

This REQUIRED attribute gives the name of the file that contains
the applet's compiled Applet subclass. This file is relative to
the base URL of the applet. It cannot be absolute.
One of CODE or OBJECT must be present. The value appletFile can
be of the form classname.class or of the form
packagename.classname.class.

OBJECT = serializedApplet

This attribute gives the name of the file that contains a
serialized representation of an Applet. The Applet will be
deserialized. The init() method will *not* be invoked;
but its start() method will. Attributes valid when the
original object was serialized are *not* restored.
Any attributes passed to this APPLET instance will be available
to the Applet; we advocate very strong restraint in using this feature.
An applet should be stopped before it is serialized.
One of CODE or OBJECT must be present.

ALT = alternateText

This OPTIONAL attribute specifies any text that should be
displayed if the browser understands the APPLET tag but can't
run Java applets.

NAME = appletInstanceName

This OPTIONAL attribute specifies a name for the applet instance,
which makes it possible for applets on the same page to find (and
communicate with) each other.

WIDTH = pixels HEIGHT = pixels

These REQUIRED attributes give the initial width and height (in
pixels) of the applet display area, not counting any windows or
dialogs that the applet brings up.

ALIGN = alignment

This OPTIONAL attribute specifies the alignment of the applet.
The possible values of this attribute are the same as those for
the IMG tag: left, right, top, texttop, middle, absmiddle,
baseline, bottom, absbottom.

VSPACE = pixels HSPACE = pixels

These OPTIONAL attributes specify the number of pixels above and
below the applet (VSPACE) and on each side of the applet (HSPACE).
They're treated the same way as the IMG tag's VSPACE and HSPACE
attributes.

<PARAM NAME = appletAttribute1 VALUE = value>

<PARAM NAME = appletAttribute2 VALUE = value> . . .

This tag is the only way to specify an applet-specific attribute.
Applets access their attributes with the getParameter() method.








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