Attributes are key-value pairs you can attach to an object like:

• ServletRequest
• HttpSession
• ServletContext

They are used to share data between:

• Different parts of your servlet (methods, filters)
• Different servlets
• Requests across time (session)

🔥 Why Use Attributes?

• Pass information between servlets when forwarding or including.
• Share objects (like database connections, user info, calculation results).
• Avoid putting sensitive data into URL or forms (more secure).

⚙️ Where You Can Store Attributes:

Object	Lifetime	Scope	Example
ServletRequest	Only during the current request	Short (request-level)	Passing a result from Servlet A to Servlet B when forwarding
HttpSession	Until session timeout or logout	Medium (user-level)	Saving user login info
ServletContext	Until server restarts or undeploys	Long (application-level)	Sharing application-wide settings

🛠️ How to Work With Attributes

1. On Request (ServletRequest)

✅ Set attribute:

request.setAttribute("userName", "Alice");

✅ Get attribute:

String name = (String) request.getAttribute("userName");

✅ Remove attribute:

request.removeAttribute("userName");

2. On Session (HttpSession)

✅ Set attribute:

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

✅ Get attribute:

String name = (String) session.getAttribute("userName");

✅ Remove attribute:

session.removeAttribute("userName");

3. On Application Context (ServletContext)

✅ Set attribute:

ServletContext context = getServletContext();
context.setAttribute("appName", "My Cool App");

✅ Get attribute:

String appName = (String) context.getAttribute("appName");

✅ Remove attribute:

context.removeAttribute("appName");

🎯 Real-world Example

Suppose:

• LoginServlet authenticates user and needs to pass user’s role to DashboardServlet.

✅ In LoginServlet:

request.setAttribute("userRole", "admin");
RequestDispatcher dispatcher = request.getRequestDispatcher("/dashboard");
dispatcher.forward(request, response);

✅ In DashboardServlet:

String role = (String) request.getAttribute("userRole");
out.println("Welcome, your role is: " + role);

Boom! — No URL params needed. Cleaner and more secure. 🚀

🧩 Quick Summary:

Object	Typical Use	Scope
Request attribute	Passing data during 1 request	Short (only 1 request)
Session attribute	Storing user data across multiple requests	Medium (user session)
Context attribute	Sharing global data across app	Long (application lifetime)