JSP (JavaServer Pages) tags are special elements used inside a .jsp file to add Java logic, display data, and control how a web page is generated on the server.

Main JSP Tags

1. Directive Tag — <%@ %>

Used to provide instructions to the JSP container, such as importing Java classes or configuring the page.

<%@ page import="java.util.Date" %>

Common directives:

• page — configures the JSP page
• include — includes another file
• taglib — declares a custom/JSTL tag library

When used: Usually at the beginning of a JSP page when you need configuration or imports.

2. Declaration Tag — <%! %>

Used to declare variables and methods that become members of the generated servlet.

<%!
    int count = 0;

    public int add(int a, int b) {
        return a + b;
    }
%>

When used: When you need to declare a method or field at the JSP class level.

In modern JSP development, declarations are generally avoided in favor of Java classes/beans.

3. Scriptlet Tag — <% %>

Used to execute Java statements on the server.

<%
    String name = "John";
    int age = 20;
%>

You can also use conditions or loops:

<%
    if (age >= 18) {
        out.println("Adult");
    }
%>

When used: Historically used whenever Java logic was needed inside JSP.

Scriptlets are not recommended in modern JSP. JSTL and Expression Language (EL) are preferred.

4. Expression Tag — <%= %>

Used to display the result of a Java expression directly in the HTML response.

<%
    String name = "John";
%>

Hello, <%= name %>

Output:

Hello, John

Another example:

<p>2 + 3 = <%= 2 + 3 %></p>

Output:

2 + 3 = 5

When used: When you want to print a value into the generated HTML.

5. JSP Action Tags — <jsp:...>

These perform predefined actions during JSP processing.

For example:

<jsp:include page="header.jsp" />

This includes another JSP page.

Another common one:

<jsp:forward page="login.jsp" />

This forwards the request to another JSP page.

When used: For operations such as:

• Including another resource
• Forwarding a request
• Working with JavaBeans
• Passing parameters

6. JSP Comment — <%-- --%>

Used for comments that will not be sent to the browser.

<%-- This is a JSP comment --%>

Compare it with an HTML comment:

<!-- This comment can be seen in the HTML source -->

JSP comments are removed during JSP processing.

Easy Way to Remember

<%@  %>    → Tell JSP how to configure/process the page
<%!  %>    → Declare variables/methods
<%   %>    → Execute Java code
<%=  %>    → Display a value
<jsp: %>   → Perform a JSP action
<%-- --%>  → JSP comment

Modern JSP Development

In modern JSP applications, you will usually see EL (Expression Language) and JSTL tags instead of scriptlets.

For example:

${user.name}

is generally preferred over:

<%= user.getName() %>

because it keeps Java code out of the presentation layer.