A custom tag: iteration : Tag « JSP « Java
A custom tag: iteration
<!-- this must be added to the web application's web.xml -->
<taglib>
<taglib-uri>/java2s</taglib-uri>
<taglib-location>/WEB-INF/java2s.tld</taglib-location>
</taglib>
// create File:java2s.tld in the /WEB-INF/
<!DOCTYPE taglib
PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
"http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
<!-- a tab library descriptor -->
<taglib xmlns="http://java.sun.com/JSP/TagLibraryDescriptor">
<tlib-version>1.0</tlib-version>
<jsp-version>1.2</jsp-version>
<short-name>Java2s Simple Tags</short-name>
<!-- this tag iterates over its body a number of times -->
<tag>
<name>iterationTag</name>
<tag-class>com.java2s.IterationTag</tag-class>
<body-content>JSP</body-content>
<attribute>
<name>howMany</name>
</attribute>
</tag>
</taglib>
//compile the following code into WEB-INF\classes\com\java2s
package com.java2s;
import java.io.IOException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;
/* This tag iterates a number of times, as specified by
its "howMany" attribute.
*/
public class IterationTag extends TagSupport
{
// Code to implement the "howMany" attribute
private int howMany;
public int getHowMany()
{
return howMany;
}
public void setHowMany(int i)
{
howMany = i;
}
public int doStartTag() throws JspException
{
return EVAL_BODY_INCLUDE;
}
private int countIterations = 0;
public int doAfterBody() throws JspException
{
int retValue = (countIterations >= (howMany - 1)) ? SKIP_BODY
: EVAL_BODY_AGAIN;
try
{
JspWriter out = pageContext.getOut();
if ( countIterations < howMany)
{
int nextNumber = (int) (Math.random() * 10);
out.println(nextNumber + "<br />");
}
}
catch (IOException e)
{
System.out.println("Error in IterateTag.doAfterBody()");
e.printStackTrace();
throw new JspException(e); // throw the error to the error page (if set)
} // end of try-catch
countIterations++;
return retValue;
} // end of doAfterBody()
} // end of class IterationTag
// start comcat and load the following jsp page in browser
<%@ taglib uri="/java2s" prefix="java2" %>
<html>
<head>
<title>A custom tag: iteration</title>
</head>
<body>
output: <p />
<java2s:iterationTag howMany="5">
Here is a random number:
</java2s:iterationTag>
</body>
</html>
