JSP - JSTL Core <c:if> Tag

The JSP JSTL Core <c:if> tag is a conditional tag in the JSP Standard Tag Library (JSTL) core library. It includes a piece of content within the JSP page only if a specific condition is true.

<c:if> Tag Syntax

Syntax:

<c:if test="condition">
    content to be included if the condition is true
</c:if>

<c:if> Tag Attributes

The JSP JSTL Core <c:if> tag has only one required attribute:

Attribute Description
test This attribute defines the condition that should be evaluated. The condition is an expression, which can be a Boolean expression or a value that can be converted to a Boolean. If the condition is true, the content within the <c:if> tag will be included in the JSP page; otherwise ignored.

<c:if> Tag Example

Here is an example of how the JSP JSTL Core <c:if> tag can be used within a JSP page:

Example:

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

<html>
<head>
    <title>Example of if in core-JSTL</title>
</head>
<body>
    <c:set var="age" scope="request" value="${21}" />

    <c:if test="${age >= 18}">
        <p>You are an adult.</p>
    </c:if>
    
    <c:if test="${age < 18}">
        <p>You are not an adult.</p>
    </c:if>
</body>
</html>

Output:

You are an adult.

In this example, the JSTL core tag library is imported with the taglib directive at the top of the page. The <c:if> tag is then used to check if the value of the "age" request parameter is greater than or equal to 18. If the condition is true, the message "You are an adult" will be displayed on the page. If the condition is false, the message "You are not an adult" will be displayed on the page.

It is worth mentioning that you can use <c:choose>, <c:when>, and <c:otherwise> tags in combination with <c:if> to create more complex conditional statements.

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