HttpSession

Class 2

Intermediate Java 30-IT-397

Sessions

We've seen cookies. Let's skip over URL Rewriting, because that one is fairly easy to figure out how to implement, yet time consuming to demonstrate. Instead, let's look at HttpSessions.

In this example, we'll save session data in one form and come back to it in another.
With JSPs, the session object is already defined for us, which makes the task incredibly easy!

In this example we have four files:

A JavaBean class, Student, that holds student information.
An HTML file that collects data from the user.
A JSP file that records that instantiates an object of type Student, and saves it in the session.
Another JSP file that gets that Student object and renders the data in the browser.

Special notes...

We're not only passing data among JSPs, we're passing objects. Thus, we can make truly object-oriented web based programs with servlets and JSPs!
Just like with cookies, we can do this same thing in servlets.

The source...

sessionshtml.html: our data collection form.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<HTML>
<HEAD>
<TITLE></TITLE>
</HEAD>
<BODY>
<form name = "userinfo" method = "GET" action = "sessionsexample.jsp">
Name: <input type = "text" name = "name">
Year: <input type = "text" name = "year">
Degree: <INPUT type = "text" name = "degree">
<input type = submit>

</form>
</BODY>
</HTML>

sessionsexample.jsp: records the form data in a Student object, saves it to the session.

<%@page contentType="text/html"%>

<html>

<head><title>JSP Page</title></head>

<body>

<%-- <jsp:useBean id="beanInstanceName" scope="session" class="package.class" /> --%>
<%-- <jsp:getProperty name="beanInstanceName" property="propertyName" /> --%>

<%

// populate a bean, add it to the session.
Student student = new Student();
student.setName(request.getParameter("name"));
student.setYear(request.getParameter("year"));
student.setDegree(request.getParameter("degree"));

// Place our student in the session.
session.putValue("student", student);
%>

Congratulations <%= student.getName() %>, your registration is complete!
<br>
<a href = "sessionresults.jsp">Continue</a>

</body>
</html>

sessionresults.jsp: gets the Student object from the session, displays it.

<%@page contentType="text/html"%>

<html>

<head><title>JSP Page</title></head>

<body>

<%-- <jsp:useBean id="beanInstanceName" scope="session" class="package.class" /> --%>
<%-- <jsp:getProperty name="beanInstanceName" property="propertyName" /> --%>

<%

// get user info out of the session

Student student = (Student) session.getValue("student");

// Print out the data. Note the mix of Java and HTML.
if (student != null) { %>
    Your data:<BR>
    Name: <%= student.getName() %> <BR>
    Year: <%= student.getYear() %> <BR>
    Degree: <%= student.getDegree() %> <BR>
<% } else { %>
    There was a problem retrieving your data. Sorry, you're just plain out of luck.
<% } %>

</body>
</html>

Student.java: a JavaBean class representing a student.

package jsp;

/*
* Student.java
*
* Created on May 21, 2002, 11:43 PM
*/

/**
*
* @author default
*/
public class Student {

    /** Holds value of property year. */
    private String year;

    /** Holds value of property degree. */
    private String degree;

    /** Holds value of property name. */
    private String name;

    /** Creates a new instance of Student */
    public Student() {
    }

    /** Getter for property year.
     * @return Value of property year.
     */
    public String getYear() {
        return this.year;
    }

    /** Setter for property year.
     * @param year New value of property year.
     */
    public void setYear(String year) {
        this.year = year;
    }

    /** Getter for property degree.
     * @return Value of property degree.
     */
    public String getDegree() {
        return this.degree;
    }

    /** Setter for property degree.
     * @param degree New value of property degree.
     */
    public void setDegree(String degree) {
        this.degree = degree;
    }

    /** Getter for property name.
     * @return Value of property name.
     */
    public String getName() {
        return this.name;
    }

    /** Setter for property name.
     * @param name New value of property name.
     */
    public void setName(String name) {
        this.name = name;
    }

}

JavaBeans and JSPs

Created by: Brandan Jones December 17, 2001