The Java EE 5 Tutorial

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 5-3).

Figure 5-3 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>