How to solve this problem with JSP tag extension?

StackOverflow https://stackoverflow.com/questions/875715

  •  22-08-2019
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Question

Begining with JSP and servlet development, I have some problems with a bodyless custom tag to be inserted in a JSP page.

Steps done:

  1. Wrote and compiled successfully a CustomTag.java (extending TagSupport) in WEB-INF/classes directory;
  2. Defined the TLD file, with a very simple example, including <body-content> with an empty value for a bodyless tag;
  3. Used the tag in a JSP page with taglib directive pointing to my /WEB-INF/tlds/site.tld file.

With all this in mind, do you have a clue why Tomcat is sending an error like this:

CustomTag cannot be resolved to a type

Thanks in advance for your answers, and please ask if you need more details.

Here's my TLD file:

<?xml version="1.0" encoding="ISO-8859-1"?>

< ! DOCTYPE taglib 
    PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN" 
    "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">

<taglib>
    <tlib-version>1.0</tlib-version>
    <jsp-version>1.2</jsp-version>
    <short-name>customlib</short-name>
    <description>Custom library.</description>
    <tag>
      <name>header</name>
      <tag-class>HeaderTag</tag-class>
      <body-content>empty</body-content>
      <description>...</description>
    </tag>
</taglib>

The JSP file:

<%@ page contentType="text/html; charset=UTF-8" language="java" import="java.sql.*" errorPage="" %>
<%@ taglib uri="/WEB-INF/tlds/customlib.tld" prefix="clib" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org    /TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>title</title>
</head>

<body>
    <clib:header />
</body>
</html>

The HeaderTag class:

import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.tagext.TagSupport;
import java.io.IOException;

public class HeaderTag extends TagSupport {

    public int doEndTag() throws JspTagException {
        try {
            pageContext.getOut().print("<p>header</p>");
        }
        catch (IOException e) {
            throw new JspTagException("Error.");
        }
        return EVAL_PAGE;
    }
}
Was it helpful?

Solution

You've rebuilt and redeployed, correct? In that case my best guess is that you left out the <tag-class> directive in the TLD file.

<tag>
    <name>cookieIterator</name>
    <tag-class>util.infoTemplates.CookieIterator</tag-class>
    <body-content>JSP</body-content>
</tag>

If that isn't the cause, please post your TLD file and an example JSP.

Edit: All tag classes must have a package. Per the JSP 2.0 spec (section JSP 11.2):

As of JSP 2.0, it is illegal to refer to any classes from the unnamed (a.k.a. default) package.

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