在jsp中映射自定义标记时出错

Question

When i try map custom tag, i am getting Error: 500 with a message File "/customTag" not found

Here is my attempt: myTag.tld

<taglib version="2.0" xmlns="http://java.sun.com/xml/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
    >
    <uri>customTag</uri>
    <tlib-version>1.0</tlib-version>
    <tag>
        <name>multiplier</name>
        <tag-class>myPack.MultiplierTag</tag-class>
        <attribute>
                <name>input</name>
                <required>true</required>
                <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>

</taglib>

jsp page

<%@taglib uri="/customTag" prefix="operator"%>
<%
    String input = request.getParameter("input");
%>
<operator:multiplier input="<%=input%>"></operator:multiplier>

When i am trying to access .tld file using file name then everything is fine

Answer 1

In TLD file: Add short-name and change uri from customTag to /customTag

<short-name>operator</short-name>
<uri>/customTag</uri>

In JSP

<@ taglib prefix="operator" uri="/customTag" />

Answer 2

I am not JEE expert but I just created my own tld based on your example and example from Head First: Servlets and JSP and it seems that:

• in uri you need to specify name that you will use in <%@taglib uri="..." so if it is <uri>customTag</uri> then you need to use it as <%@taglib uri="customTag"
• your tag doesn't specify body-content , which for your example can be set to empty

So try with this tld which you can place in /WEB-INF/tlds/myTag.tld

<taglib version="2.0" xmlns="http://java.sun.com/xml/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd">
    <uri>customTag</uri>
    <tlib-version>1.0</tlib-version>
    <tag>
        <name>multiplier</name>
        <tag-class>myPack.MultiplierTag</tag-class>
        <body-content>empty</body-content>
        <attribute>
                <name>input</name>
                <required>true</required>
                <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
</taglib>

For implementation you can use

package myPack;

import java.io.IOException;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.SimpleTagSupport;

public class MultiplierTag extends SimpleTagSupport {
    private String input;

    public void doTag() throws JspException, IOException {
        getJspContext().getOut().write("Hello " + input + " <br>");
    }

    public void setInput(String input) {
        this.input = input;
    }
}

and for demonstration you can use your earlier JSP

<%@taglib uri="customTag" prefix="operator"%>
<%
    String input = "World";//request.getParameter("input");
%>
<operator:multiplier input="<%=input%>"></operator:multiplier>

Don't forget to republish your project after updating it.