Applet Antics - Java

One of the most exciting features about JSP is the ability tobuild and use custom "tag libraries" in your JSP applications. In thisarticle, find out why tag libraries are a Good Thing, and read about how toget and install custom tag libraries for common tasks.

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By: Vikram Vaswani and Harish Kamath, (c) Melonfire

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June 11, 2001

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TOOLS YOU CAN USE

You've already seen how JSP "actions" work - in the last article, for example, we demonstrated the <jsp:useBean> and <jsp:setProperty> actions in conjunction with JavaBeans, while <jsp:include> was illustrated in the very first article in this series. However, we missed out on a couple of important ones - and so, we'd like to introduce you to <jsp:plugin>, used to incorporate Java applets into a Web page.

The <jsp:plugin> directive takes care of generating all the HTML code necessary to embed and activate a Java applet. Consider the following example:


<html>
<head>
</head>
<body>
<jsp:plugin type="applet" code="NewsTicker.class" name="newsticker"
height="100" width="100">
<jsp:params>
<jsp:param name="x" value="10"/>
<jsp:param name="y" value="25"/>
<jsp:param name="cx" value="90"/>
<jsp:param name="cy" value="114"/>
<jsp:param name="bgcolor" value="102,102,153"/>
<jsp:param name="textcolor" value="0,0,0"/>
<jsp:param name="hilitecolor" value="255,0,0"/>
</jsp:params>
<jsp:fallback>Oops! Something bad happened and I can't display this
applet</jsp:fallback>
</jsp:plugin>
</body>
</html>

The code above sets up the applet contained in "NewsTicker.class", and passes it a bunch of name-value pairs of parameters. The
When JSP compiles and renders the page, the code above is automatically converted to its HTML equivalent.



<html>
<head>
</head>
<body>
<OBJECT classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93" width="100"
height="100"
codebase="http://java.sun.com/products/plugin/1.2.2/jinstall-1_2_2-win.cab
#Version=1,2,2,0">
<PARAM name="java_code" value="NewsTicker.class">
<PARAM name="type" value="application/x-java-applet;">
<PARAM name="cy" value="114">
<PARAM name="cx" value="90">
<PARAM name="bgcolor" value="102,102,153">
<PARAM name="hilitecolor" value="255,0,0">
<PARAM name="y" value="25">
<PARAM name="x" value="10">
<PARAM name="textcolor" value="0,0,0">
<COMMENT>
<EMBED type="application/x-java-applet;"  width="100"  height="100"
pluginspage="http://java.sun.com/products/plugin/"
java_code="NewsTicker.class"
cy=114
cx=90
bgcolor=102,102,153
hilitecolor=255,0,0
y=25
x=10
textcolor=0,0,0
>
<NOEMBED>
</COMMENT>
Oops! Something bad happened and I can't display this applet
</NOEMBED></EMBED>
</OBJECT>
</body>
</html>

And finally, the


<jsp:forward page="endzone.jsp" />

Just as in the previous example, additional parameters can be passed to the new script via <jsp:param>. For example,


<jsp:forward page="endzone.jsp">
<jsp:param name="user" value="joe" />
<jsp:param name="uid" value="653" />
<jsp:param name="gid" value="1220" />
</jsp:forward>

And with that, it's about time to call this a wrap. We hope you enjoyed it, and that it served as a good starting point for your entry into the world of JSP.

If you're interested in learning more about the topics discussed in this series, take a look at Sun Microsystems' JSP pages at http://java.sun.com/products/jsp/, Java documentation and references at http://java.sun.com/docs/, or the tutorial on tag libraries at http://java.sun.com/products/jsp/tutorial/TagLibrariesTOC.html. If, on the other hand, you have questions, comments, or large sums of money for us, drop us a line - we'd love to hear from you!

Until next time...stay healthy!