Relational Operators in JSTL

JSTL provides comparison operators that can be used within EL expressions:

• -lt — less than
• -le — less than or equal to
• -gt — greater than
• -ge — greater than or equal to
• -eq — equal to
• -ne — not equal to

Checking for null or empty values:

<c:if test="${empty items}">
    <!-- Handle empty case -->
</c:if>

Pratcical Examples

Example 1: Comparing loop counter with request parameter

<c:forEach var="index" begin="1" end="${maxIterations}">
    <c:if test="${selectedIndex eq index}">
        <a href="product_detail.action?id=${index}" style="color: #000">[${index}]</a>
    </c:if>
    <c:if test="${selectedIndex ne index}">
        <a href="product_detail.action?id=${index}" style="color: red">[${index}]</a>
    </c:if>
</c:forEach>

Example 2: Using c:choose for if-else logic

<c:choose>
    <c:when test="${selectedIndex eq currentIndex}">
        Selected item: ${currentIndex}
    </c:when>
    <c:otherwise>
        Unselected item: ${currentIndex}
    </c:otherwise>
</c:choose>

Example 3: Iterating with status and conditional display

<c:forEach items="${productList}" var="product" varStatus="loopStatus">
    <li>
        <c:if test="${loopStatus.index < 4}">
            <a href="product_details.action?id=${product.id}">
                <img src="${product.imageUrl}">
            </a>
            <div class="product-name">${product.name}</div>
            <div class="price">¥${product.cost}</div>
        </c:if>
    </li>
</c:forEach>

Using c:choose for Conditional Logic

When you need if-else functionality rather than just if, use <c:choose> with <c:when> and <c:otherwise>:

<c:choose>
    <c:when test="${condition1}">
        First condition is true
    </c:when>
    <c:when test="${condition2}">
        Second condition is true
    </c:when>
    <c:otherwise>
        No conditions matched
    </c:otherwise>
</c:choose>

Key points:

• <c:otherwise> must appear after all <c:when> tags within a <c:choose>
• If no <c:when> tests evaluate to true, the <c:otherwise> block executes
• Each <c:choose> can have only one <c:otherwise>