Custom JSP tags allow you to create your own new JSP tag (like <my:hello /> or <my:showDate />) that encapsulates Java logic cleanly,
instead of mixing Java code (<% %>) directly into your JSP pages.

✅ It helps you extend JSP functionality, reuse common logic, and keep JSPs clean and readable.

✅ Custom tags are server-side components that are executed during JSP processing.

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🔥 Why Write Custom Tags?

Benefit	Reason
Cleaner JSP code	No messy Java code (<% %>)
Reusable components	Write once, use everywhere
Separation of concerns	Keep logic out of presentation
Easy for designers	Designers can use tags without needing Java knowledge
Consistency	Same logic, same output everywhere

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🛠️ How to Write a Simple Custom Tag?

There are two main ways:

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🔵 1. Using a Java Class (Tag Handler Class)

✅ You write a Java class that extends one of the following:

Class	Use Case
SimpleTagSupport	For simple tags (JSP 2.0 and newer) — recommended
TagSupport	For older-style, more complex tags
BodyTagSupport	For tags that operate on body content

Simple Example:

Step 1: Java Class

package mytags;

import javax.servlet.jsp.tagext.SimpleTagSupport;
import javax.servlet.jsp.JspWriter;
import java.io.IOException;

public class HelloTag extends SimpleTagSupport {
    public void doTag() throws IOException {
        JspWriter out = getJspContext().getOut();
        out.print("Hello from a custom tag!");
    }
}

Step 2: Create a Tag Library Descriptor (TLD) File

Create a mytags.tld inside /WEB-INF/.

<?xml version="1.0" encoding="UTF-8" ?>
<taglib xmlns="http://java.sun.com/xml/ns/javaee"
        version="2.1">
    <tlib-version>1.0</tlib-version>
    <short-name>MyTags</short-name>
    <uri>http://example.com/mytags</uri>

    <tag>
        <name>hello</name>
        <tag-class>mytags.HelloTag</tag-class>
        <body-content>empty</body-content>
    </tag>
</taglib>

Step 3: Use Your Tag in a JSP

<%@ taglib uri="http://example.com/mytags" prefix="my" %>

<my:hello />

✅ Outputs:

Hello from a custom tag!

🔵 2. Using Tag Files (.tag)

✅ A faster and simpler way to create tags without Java coding if your logic is simple.

How?

• Create a .tag file inside /WEB-INF/tags/.
• Write normal JSP content inside it.

Example:

File: /WEB-INF/tags/hello.tag

Hello from a tag file!

Use it in JSP:

<%@ taglib tagdir="/WEB-INF/tags" prefix="my" %>

<my:hello />

✅ Much quicker — no Java classes needed!

🎯 Summary: Two Ways to Write Custom Tags

Approach	Best When	Notes
Tag Handler Class (Java class + TLD)	More complex, reusable, parameterized logic	Full power
Tag File (.tag)	Simple reusable templates	Quick and easy

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📢 Important Advanced Points:

• You can pass attributes to custom tags (like <my:hello name="Stanley" />) by writing setters in Java class or by using attribute directive in .tag files.
• You can handle body content (the text between start and end tags) using BodyContent in classic tag handlers or <jsp:doBody /> in tag files.
• Modern JSP prefers SimpleTagSupport + .tag files style (easier and cleaner).

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🚀 Real-World Usage

You typically create custom tags for:

• UI components (menus, buttons, panels)
• Formatting (dates, currencies)
• Custom access control (show/hide content for users with specific roles)
• Common layouts (headers, footers, sections)

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📜 Quick Comparison to Built-in Tags

Type	Example
Built-in tag (JSTL)	<c:forEach>, <c:if>
Your custom tag	<my:hello>, <my:showDate>

✅ Same usage style, but you control the behavior!