Using the object Tag - Java Tutorial 5.0 英文版

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Trail: Deployment
Lesson: Applets

Using the object Tag

You use the object tag to deploy applets that are to be used only with Internet Explorer.
For complete details on the object tag, read the W3 HTML specification.
Following is an example of the object tag:
<OBJECT 
  classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
  width="200" height="200">
  <PARAM name="code" value="Applet1.class">
</OBJECT>

The classid Attribute

The classid attribute identifies which version of Java Plug-in to use.

The example shown below is the most commonly used form of the classid attribute. This example instructs Internet Explorer to use the latest installed version of Java Plug-in.
classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93" 
Following is an alternative form of the classid attribute:
&BEGINCODE classid="clsid:CAFEEFAC-xxxx-yyyy-zzzz-ABCDEFFEDCBA" &ENDCODE
In this form, "xxxx", "yyyy", and "zzzz" are four-digit numbers that identify the specific version of Java Plug-in to be used.

For example, to use Java Plug-in version 1.5.0, you specify:
classid="clsid:CAFEEFAC-0015-0000-0000-ABCDEFFEDCBA" 

The codebase Attribute

You use the optional codebase attribute to specify the location to download JRE from in case it is not installed on the system.

The codebase attribute has two forms:

codebase=<URL>

With this form, if the JRE specified by the classid attribute is not installed locally, then the user is prompted to download the JRE from the URL specified.

codebase=<URL>#Version=major,minor,micro,update

With this form, Java Plug-in compares the classid of the locally installed JRE with the required version of JRE, and if the required version is higher, prompts the user to download and install the newer version of the JRE.

Following is an example of how to use the codebase attribute to set up automatic downloads from the Sun Java Web site:
<object 
  classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
  width="200" height="200"
  codebase="http://java.sun.com/products/plugin/autodl/
           jinstall-1_5_0-windows-i586.cab#Version=1,5,0,0">
  <param name="code" value="Applet1.class">
</object>
Note: In this example the codebase=http://java.sun.com ... line is broken for readability. In the actual HTML file it would be one long line.

Sun has packaged each version of the JRE installer in Microsoft cabinet (.cab) file format. You can view a list of these releases and the corresponding .cab file names.

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