Model View Controller (MVC) with JSP and JSTL

In this article we will create a small web application that uses the Model View Controller (MVC) pattern with Java Server Pages (JSP) and JSP Standard Template Library (JSTL). A container like Tomcat is needed to run this combination.

Thanks go out to the author of the JSP – MVC Tutorial, who thought of the sample application that we will use here, the coffee advisor. The user is first presented with a choice in coffee taste she prefers. Pressing a button moves on to a page with advise about the type of coffee to drink based on that taste.

An MVC application has three parts:

Model. The model is the domain-specific representation of the data upon which the application operates. In our case this is implemented in the CoffeeExpert class.
View. The view renders the model into a form suitable for interaction, typically a user interface element. In our case this is implemented in a JSP file called coffee.jsp.
Controller. The controller receives input and initiates a response by making calls on model objects. In our case this is implemented in the CoffeeSelect class.

In addition to these three file we need a web.xml file that tells the container how to map a URL (e.g. /CoffeeSelect.do) into a class to run (e.g. com.example.web.CoffeeSelect). We also need a start page for the user input, which we will call coffee.html. In total this means we should create a .war file with the following structure:

coffee.html

<html>
    <body>
        <h2>Coffee Advisor Input</h2>
        <form method="POST" action="CoffeeSelect.do">
            <select name="taste" size=1">
                <option value="milky">Milky</option>
                <option value="froffy">Froffy</option>
                <option value="icey">Icey</option>
                <option value="strong">Spaced Out</option>
            </select>
            <br/><br/>
            <input type="Submit"/>
        </form>
    </body>
</html>

CoffeeExpert.java

package com.example.model;

import java.util.*;

public class CoffeeExpert {
    public List<String> getTypes(String taste) {
        List<String> result = new ArrayList<String>();
        if (taste.equals("milky")) {
            result.add("Latte");
            result.add("Cappuccino");
        } else if (taste.equals("froffy")) {
            result.add("Latte");
            result.add("Cappuccino");
            result.add("Frappuccino");
        } else if (taste.equals("icey")) {
            result.add("Frappuccino");
        } else if (taste.equals("strong")) {
            result.add("Espresso");
            result.add("Double espresso");
        } else {
            result.add("Vending machine");
        }
        return (result);
    }
}

CoffeeSelect.java

package com.example.web;

import java.io.IOException;
import java.util.List;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.example.model.CoffeeExpert;

public class CoffeeSelect extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
        List<String> types = new CoffeeExpert().getTypes(request.getParameter("taste"));
        request.setAttribute("types", types);
        RequestDispatcher view = request.getRequestDispatcher("coffee.jsp");
        view.forward(request, response);
    }
}

coffee.jsp

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

<html>
    <body>
        <h2>Coffee Advisor Output</h2>
        <c:forEach var="type" items="${types}">
            <c:out value="${type}"/>
            <br />
        </c:forEach>
    </body>
</html>

web.xml

<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
    version="2.4">

    <servlet>
        <servlet-name>Coffee</servlet-name>
        <servlet-class>com.example.web.CoffeeSelect</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>Coffee</servlet-name>
        <url-pattern>/CoffeeSelect.do</url-pattern>
    </servlet-mapping>
</web-app>

3 Responses to Model View Controller (MVC) with JSP and JSTL

david says:

28/06/2011 at 14:19

Awesome article!

Anmol Vats says:

27/04/2012 at 14:24

Thanks a ton guys.
Very Useful information for a Beginner.
Keep Blogging…

C says:

06/09/2012 at 10:42

Finally a complete code that works!
Thank you! More! :D