Professional Java Server Programming J2EE Edition
Chapter 12
// This method will be called when the JSP engine encounters
// the start of a tag implemented by this class
public int doStartTag() throws JspTagException {
// This return value means that the JSP engine
// should evaluate the contents and any child
//tags of this tag
return EVAL_BODY_INCLUDE;
}
// This method will be called when the JSP engine encounters
// the end of a tag implemented by this class
public int doEndTag() throws JspTagException {
String dateString = new Date().toString();
try {
pageContext.getOut().write("Hello world.<br/>");
pageContext.getOut().write("My name is "
+ getClass().getName() +
" and it's " + dateString + "<p/>");
} catch (IOException ex) {
throw new JspTagException
("Fatal error: hello tag could not
write to JSP out");
}
// This return value means that the JSP engine should
// continue to evaluate the rest of this page
return EVAL_PAGE;
}
} // class HelloTag
The tag library descriptor, which we'll name hello.tld, is required to map the tag to the tag handler class
and defines the way JSPs may interact with the HelloTag class. The tag library descriptor is an XML
document conforming to a DTD specified by Sun Microsystems:
<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE taglib
PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN"
"http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.1</jspversion>
<shortname>examples</shortname>
<info>Simple example library.</info>
<tag>
<name>hello</name>
<tagclass>tagext.HelloTag</tagclass>
<bodycontent>JSP</bodycontent>
<info>Simple example</info>
</tag>
</taglib>
The tag's suffix when used in JSPs must be hello, and its prefix is examples.
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