Difference between getAttribute() and getParameter

Question

What is the difference between getAttribute() and getParameter() methods within HttpServletRequest class?

Answer 1

Basic difference between getAttribute() and getParameter() is the return type.

java.lang.Object getAttribute(java.lang.String name)
java.lang.String getParameter(java.lang.String name)

Answer 2

The difference between getAttribute and getParameter is that getParameter will return the value of a parameter that was submitted by an HTML form or that was included in a query string. getAttribute returns an object that you have set in the request, the only way you can use this is in conjunction with a RequestDispatcher. You use a RequestDispatcher to forward a request to another resource (JSP / Servlet). So before you forward the request you can set an attribute which will be available to the next resource.

Answer 3

Another case when you should use .getParameter() is when forwarding with parameters in jsp:

<jsp:forward page="destination.jsp">
    <jsp:param name="userName" value="hamid"/>
</jsp:forward>

In destination.jsp, you can access userName like this:

request.getParameter("userName")

Answer 4

Generally, a parameter is a string value that is most commonly known for being sent from the client to the server (e.g. a form post) and retrieved from the servlet request. The frustrating exception to this is ServletContext initial parameters which are string parameters that are configured in web.xml and exist on the server.

An attribute is a server variable that exists within a specified scope i.e.:

• application, available for the life of the entire application
• session, available for the life of the session
• request, only available for the life of the request
• page (JSP only), available for the current JSP page only