How do you store Java objects in HttpSession?

Question

So I am trying to get a servlet to add a Java object to the session of the user, when this servlet is requested. But after the servlet redirects to the next page and I try to retrieve the object, I get a null object instead.

Here is what I do to add the object to the HttpSession (in the servlet):

request.setAttribute("object", obj); 

Then I try to retrieve it by (in the JSP):

 Object obj = request.getAttribute("object"); 

So how would I get obj to not be null?

Update: I have also tried this with nothing:

HttpSession session = request.getSession(); session.setAttribute("object", obj); 

with the following in the JSP:

 Object obj = request.getSession().getAttribute("object"); 

Both ways still return null.

Answer 1

You are not adding the object to the session, instead you are adding it to the request.
What you need is:

HttpSession session = request.getSession(); session.setAttribute("MySessionVariable", param); 

In Servlets you have 4 scopes where you can store data.

1. Application
2. Session
3. Request
4. Page

Make sure you understand these. For more look here

Answer 2

Add it to the session, not to the request.

HttpSession session = request.getSession(); session.setAttribute("object", object); 

Also, don't use scriptlets in the JSP. Use EL instead; to access object all you need is ${object}.

A primary feature of JSP technology version 2.0 is its support for an expression language (EL). An expression language makes it possible to easily access application data stored in JavaBeans components. For example, the JSP expression language allows a page author to access a bean using simple syntax such as ${name} for a simple variable or ${name.foo.bar} for a nested property.