Including an Applet

You can include an applet or a JavaBeans component in a JSP page by using the jsp:plugin element. This element generates HTML that contains the appropriate client-browser-dependent construct (<object> or <embed>) that will result in the download of the Java Plug-in software (if required) and the client-side component and in the subsequent execution of any client-side component. The syntax for the jsp:plugin element is as follows:

<jsp:plugin 
 type="bean|applet" 
 code="objectCode" 
 codebase="objectCodebase" 
 { align="alignment" } 
 { archive="archiveList" } 
 { height="height" } 
 { hspace="hspace" } 
 { jreversion="jreversion" } 
 { name="componentName" } 
 { vspace="vspace" } 
 { width="width" } 
 { nspluginurl="url" } 
 { iepluginurl="url" } > 
 { <jsp:params> 
  { <jsp:param name="paramName" value= paramValue" /> }+
 </jsp:params> } 
 { <jsp:fallback> arbitrary_text </jsp:fallback> } 
</jsp:plugin>

The jsp:plugin tag is replaced by either an <object> or an <embed> tag as appropriate for the requesting client. The attributes of the jsp:plugin tag provide configuration data for the presentation of the element as well as the version of the plug-in required. The nspluginurl and iepluginurl attributes override the default URL where the plug-in can be downloaded.

The jsp:params element specifies parameters to the applet or JavaBeans component. The jsp:fallback element indicates the content to be used by the client browser if the plug-in cannot be started (either because <object> or <embed> is not supported by the client or because of some other problem).

If the plug-in can start but the applet or JavaBeans component cannot be found or started, a plug-in-specific message will be presented to the user, most likely a pop-up window reporting a ClassNotFoundException.

The Duke's Bookstore page /template/prelude.jspf creates the banner that displays a dynamic digital clock generated by DigitalClock (see Figure 12-3).

[画像:Duke's Bookstore with Applet]

Figure 12-3 Duke's Bookstore with Applet

Here is the jsp:plugin element that is used to download the applet:

<jsp:plugin 
 type="applet" 
 code="DigitalClock.class" 
 codebase="/bookstore2" 
 jreversion="1.4" 
 align="center" height="25" width="300"
 nspluginurl="http://java.sun.com/j2se/1.4.2/download.html" 
 iepluginurl="http://java.sun.com/j2se/1.4.2/download.html" >
 <jsp:params>
  <jsp:param name="language"
   value="${pageContext.request.locale.language}" />
  <jsp:param name="country"
   value="${pageContext.request.locale.country}" />
  <jsp:param name="bgcolor" value="FFFFFF" />
  <jsp:param name="fgcolor" value="CC0066" />
 </jsp:params>
 <jsp:fallback>
  <p>Unable to start plugin.</p>
 </jsp:fallback>
</jsp:plugin>