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 43).

Figure 43. 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>