The APPLET Tag

To add an applet to an HTML page, use the APPLET tag. This page provides a couple of examples, then defines the complete syntax of the APPLET tag, including a description of each of the tag's attributes.

## A Simple Example

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

This example tells the 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.

## A More Complex Example

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

This tells the browser to load the applet whose compiled code is at the URL http://java.sun.com/applets/NervousText/1.1/NervousText.class, and to set the initial size of the applet to 400 pixels wide by 75 pixels high. The browser must also set the applet's "text" parameter (which specifies the text this applet displays) to be "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 a bit 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.

## The APPLET Tag Syntax

Required elements are in bold. Optional elements are in regular typeface. Elements you specify are in italics.

        <APPLET
            CODEBASE = codebaseURL
            CODE = appletFile ...or... OBJECT = serializedApplet
            WIDTH = pixels  HEIGHT = pixels
            NAME = appletInstanceName
            ALIGN = alignment
            VSPACE = pixels  HSPACE = pixels
            ARCHIVE = archiveList
            ALT = alternateText
        >
        <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 (or OBJECT), WIDTH, and HEIGHT. Each attribute is described below.

CODEBASE = codebaseURL
  This optional attribute specifies the base URL of the applet. This is where the browser looks to find the .class file defined by the CODE attribute. If you don't specify CODEBASE, the browser looks for the .class file in the same directory as the HTML file containing the applet tag.

CODE = appletFile
  This required attribute is the name of the file that contains the compiled applet. This is always a file with a .class extension. For example, to include an applet called MyApplet in an HTML page, you would specify:

          CODE="MyApplet.class"

OBJECT = serializedApplet
  This attribute is an alternative to the CODE attribute. (Either CODE should be used, or OBJECT, but not both.) OBJECT gives the name of a file that contains a serialized applet. This is a "snapshot" of an applet that has been previously started and stopped. When the applet is serialized, its current state is captured to be restarted at a later time. For example, a game applet might be serialized and restarted at a later time from the point in the game where the applet was stopped.

  NOTE: The attributes valid when the applet was previously started, such as WIDTH, HEIGHT, and the PARAM attributes, are not saved when the applet is serialized. The attributes passed to this instance of the applet may be different than the original attributes, which could potentially cause unexpected behavior.

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

NAME = appletInstanceName
  This optional attribute specifies a unique name for this instance of the applet, which makes it possible for applets on the same page to find (and communicate with) each other.

ALIGN = alignment
  This optional attribute specifies the alignment of the applet with the text that surrounds it. If you don't specify this attribute, the bottom of the applet is typically aligned with the bottom of the adjacent text, but this can vary among browsers. 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 option 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.

ARCHIVE = archiveList
  This optional attribute is a list of one or more JAR (Java Archive) files containing resources the applet will reference, such as classes (java code) and images. The advantage of using archives is to minimize the number of HTTP accesses to obtain resources. The archive file is preloaded before the applet is run; then when the applet needs a resource, it searches the preloaded archives first.

  If you have more than one archive files, separate each file with a , (comma).

ALT = alternateText
  This optional attribute specifies any text that should be displayed if the browser can generally run Java applets, but it can't display this particular applet (for example, if this applet can't be loaded).

<PARAM NAME = appletAttribute1 VALUE = value>
<PARAM NAME = appletAttribute2 VALUE = value> . . .
  Use this tag to specify applet-specific attributes. The applet writer specifies what (if any) parameters the applet accepts or requires. Some applets have no parameters, while others might require that you specify several.

alternateHTML
  This optional HTML at the end of the applet tag specifies any text that should be displayed if the browser understands the APPLET tag but can't run Java applets. In the example at the top of this page, the alternateHTML was the HTML between, and including, the <hr> tags.

When the user-specified attributes are text, such as codebaseURL, it is generally a good idea to enclose the text in double quotes, as was done in the examples in this document. This will insure that browsers won't have problems parsing the text.

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