JSTL forEach Tag <c:forEach>

JSTL forEach tag is used to iterate over the collection. It can be List, Set, ArrayList, HashMap or any other collection.

These tags exist as a good alternative to embedding a Java for, while, or do-while loop via a scriptlet. The <c:forEach> tag is the more commonly used tag because it iterates over a collection of objects. The <c:forTokens> tag is used to break a string into tokens and iterate through each of the tokens.

JSTL <c:forEach> Example:
To display the name of the product on JSP, you can use the <c:forEach> tag like:</div>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<html>
<head>
<title>c:remove Tag Example</title>
</head>
<body>
<c:forEach items="${employeeList}" var="employee" varStatus="status">
    <c:out value="${employee.name}" default="Not Available" escapeXml="false"></c:out>
  </c:forEach>

  <c:forEach items="${employeeList}" var="i" varStatus="status" begin="1" end="5">
     Employee <c:out value="${i}"/><p>
  </c:forEach>
  
</body>
</html>

The above statement assumes that employeeList object is available on this JSP and that employee bean has a property name with setters and getter.

As you can see above, in the JSTL forEach tag, items attribute is used to define the collection. It will iterate over employeeList. In each iteration, it will get a employee variable defined with attribute var. status attribute keeps track of iteration.

Withing starting and ending tag of forEach, you can display or apply other logic to each object in the collection. As shown in the above example, product name is displayed with index using c:out tag


Attributes of JSTL <c:forEach> tag are:
1. items:This attribute provides collection of items to iterate over.

2. var: This attribute provides name of the exported scoped variable for the current item of the iteration. This scoped variable has nested visiblity. Its type depends on the object of the underlying collection.

3. varStatus: This attribute provides name of the exported scoped variable for the status of the iteration. Object exported is of type javax.servlet.jsp.jstl.core.LoopTagStatus. This scoped variable has nested visibility.

4. begin: If items specified: Iteration begins at the item located at the specified index. First item of the collection has index 0. If items not specified: Iteration begins with index set at the value specified.

5. end: If items specified: Iteration ends at the item located at the specified index (inclusive). If items not specified: Iteration ends when index reaches the value specified.

6. step: Iteration will only process every step items of the collection, starting with the first one.

Iterate over HashMap:

Let's take another example which many people face during coding of real web application. Many times you get HashMap and need to iterate over it. In the example below, I take Map of Country Code and Currency, where country code is unique and selected as a key and currency is a value.

<c:forEach items="${countryCurrencyMap}" var="entry" varStatus="status>
    <c:out value="${entry.key}"> : <c:out value="${entry.value}">
 </c:forEach>



<<Previous <<   || Index ||   >>Next >>







No comments:

Post a Comment