How do I share object or data between users in web application?

In a web application there are different type of scope where we can store object or data. There are a page, request, session and application scope.

To share data between users of the web application we can put shared object in application scope which can be done by calling setAttribute() method of the ServletContext. By this way data can then be accessing by other users by calling the getAttribute() method of the ServletContext.

Let’s see the example code in a simple servlet.

package org.kodejava.example.servlet;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class ApplicationContextScopeAttribute extends HttpServlet {

    protected void doGet(HttpServletRequest req, HttpServletResponse res) 
            throws ServletException, IOException {

        ServletContext context = this.getServletContext();
        context.setAttribute("HELLO.WORLD", "Hello World 123");
    }
}

And here is what we code in the JSP page to access it.

<%= getServletContext().getAttribute("HELLO.WORLD") %>