JSTL - Learn Java by Examples

How do I forward to other page using <jsp:forward>?

By Wayan in Taglib Last modified: May 24, 2023 0 Comment

The <jsp:forward/> tag forward user request to other page. For example, a user request page1.jsp and in this page the server found a <jsp:forward page="page2.jsp"/>. The server immediately stop the processing of page1.jsp and jump to the page2.jsp.

Let see an example of using <jsp:forward/> tag.

page1.jsp

<%@ page contentType="text/html;charset=UTF-8" %>
<!DOCTYPE html>
<html lang="en">
<head>
    <title>Page 1</title>
</head>
<body>
<strong>This is page 1</strong>

<jsp:forward page="page2.jsp"/>
</body>
</html>

page2.jsp

<%@ page contentType="text/html;charset=UTF-8" %>
<!DOCTYPE html>
<html lang="en">
<head>
    <title>Page 2</title>
</head>
<body>
<strong>This is page 2</strong>
</body>
</html>

When you try to run the example above by accessing the URL http://localhost:8080/forward/page1.jsp you are going to see the content of page2.jsp instead of page1.jsp. It’s happen because on the server side page1.jsp forward your request to the page2.jsp. But if you look at your browser URL address it will still point to page1.jsp.

Here is the directory structure of our example:

.
├─ pom.xml
└─ src
   └─ main
      └─ webapp
         └─ forward
            └─ page1.jsp
            └─ page2.jsp

Maven Dependencies

<dependency>
  <groupId>javax.servlet</groupId>
  <artifactId>jstl</artifactId>
  <version>1.2</version>
</dependency>

How do I include other pages using <jsp:include>?

By Wayan in Taglib Last modified: May 24, 2023 0 Comment

The <jsp:include/> tag is use for including another page fragment of a JSP page into another page. This is useful when you have a common page such as header, footer or a menu that applied to many of all of your pages.

<%@ page contentType="text/html;charset=UTF-8" %>
<!DOCTYPE html>
<html lang="en">
<head>
    <title><jsp:include/> Demo</title>
</head>
<body>
<div id="header">
    <jsp:include page="include/common/header.jsp"/>
</div>

<div id="main">
    Lorem ipsum dolor sit amet, consectetur adipisicing elit,
    sed do eiusmod tempor incididunt ut labore et dolore magna
    aliqua.
</div>

<div id="footer">
    <jsp:include page="include/common/footer.jsp"/>
</div>
</body>
</html>

Here are the page fragment of the header.jsp, footer.jsp and menu.jsp. All of them are placed in the common folder in the same location with the index.jsp file.

header.jsp

<strong><jsp:include/> Demo</strong>
<hr/>
<jsp:include page="menu.jsp"/>

footer.jsp

<hr/>
© 2021 Kode Java Org

menu.jsp

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<a href="<c:url value="/index.jsp"/>">HOME</a>

When you access your page (http://localhost:8080/jsp-include-tag.jsp) from the servlet container such as Apache Tomcat you’ll have a complete display of a page that contains header, menu, content and footer.

Here is the directory structure of our example:

.
.
├─ pom.xml
└─ src
   └─ main
      └─ webapp
         ├─ include
         │  └─ common
         │     ├─ footer.jsp
         │     ├─ header.jsp
         │     └─ menu.jsp
         ├─ jsp-include-tag.jsp
         └─ index.jsp

Maven Dependencies

<dependency>
  <groupId>javax.servlet</groupId>
  <artifactId>jstl</artifactId>
  <version>1.2</version>
</dependency>

How do use <c:forEach> JSTL tag?

By Wayan in Taglib Last modified: May 24, 2023 0 Comment

The <c:forEach> tag in the core JSTL tag library is a useful tag when we want to iterate over a collection of data such as array. It is commonly used to render a tabular data in our web pages in form of HTML table.

In the example below we display a weather data that we stored as two-dimensional array of string. After declaring and initializing the data with some value we put it into the request scope. Later on the <c:forEach> tag can use the data, iterates it row by row to form an HTML table. Our weather data consist of the date, condition and the high and low temperature.

<%@ page contentType="text/html;charset=UTF-8" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html>
<html lang="en">
<head>
    <title>Weather Forecast</title>

    <style>
        table, th, td {
            border: 1px solid #000;
            border-collapse: collapse;
        }
    </style>
</head>
<body>
<%
    String[][] data = {
            {"Oct 11", "Sunny", "30", "26"},
            {"Oct 12", "Sunny", "32", "28"},
            {"Oct 13", "Sunny", "31", "27"},
            {"Oct 14", "Partly Cloudy", "29", "25"},
            {"Oct 15", "Isolated T-Storms", "27", "25"}
    };
    request.setAttribute("weathers", data);
%>
<strong>5-Days Weather for Denpasar, Indonesia</strong>

<table>
    <tr>
        <th>DATE</th>
        <th>CONDITION</th>
        <th>TEMP. HIGH</th>
        <th>TEMP. LOW</th>
    </tr>
    <c:forEach var="weather" items="${weathers}">
        <tr>
            <td>${weather[0]}</td>
            <td>${weather[1]}</td>
            <td style="text-align: center">${weather[2]}℃</td>
            <td style="text-align: center">${weather[3]}℃</td>
        </tr>
    </c:forEach>
</table>
</body>
</html>

Our JSP page above creates the following output:

5-Days Weather for Denpasar, Indonesia

DATE	CONDITION	TEMP. HIGH	TEMP. LOW
Oct 11	Sunny	30℃	26℃
Oct 12	Sunny	32℃	28℃
Oct 13	Sunny	31℃	27℃
Oct 14	Partly Cloudy	29℃	25℃
Oct 15	Isolated T-Storms	27℃	25℃

Maven Dependencies

<dependency>
  <groupId>javax.servlet</groupId>
  <artifactId>jstl</artifactId>
  <version>1.2</version>
</dependency>

How do I format a date in a JSP page?

By Wayan in Taglib Last modified: May 20, 2023 0 Comment

This example show how to format date in JSP using format tag library. We create a date object using the <jsp:useBean> taglib. To format the date we use the <fmt:formatDate> taglib. We assign the value attribute to the date object, set the type attribute as date and define the pattern how the date will be formatted.

<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt" %>
<!DOCTYPE html>
<html lang="en">
<head>
    <title>Date Format</title>
</head>
<body>
<jsp:useBean id="date" class="java.util.Date"/>
Today is: <fmt:formatDate value="${date}" type="date" pattern="dd-MMM-yyyy"/>
</body>
</html>

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>4.0.1</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>
</dependencies>