Difference between getAttribute() and getParameter()

Question

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

Answer 1

request.getParameter()

We use request.getParameter() to extract request parameters (i.e. data sent by posting a html form ). The request.getParameter() always returns String value and the data come from client.

request.getAttribute()

We use request.getAttribute() to get an object added to the request scope on the server side i.e. using request.setAttribute(). You can add any type of object you like here, Strings, Custom objects, in fact any object. You add the attribute to the request and forward the request to another resource, the client does not know about this. So all the code handling this would typically be in JSP/servlets. You can use request.setAttribute() to add extra-information and forward/redirect the current request to another resource.

For example,consider about first.jsp,

//First Page : first.jsp
<%@ page import="java.util.*" import="java.io.*"%>
<% request.setAttribute("PAGE", "first.jsp");%>

and second.jsp:

<%@ page import="java.util.*" import="java.io.*"%>
From Which Page : <%=request.getAttribute("PAGE")%>

Data From Client : <%=request.getParameter("CLIENT")%>

From your browser, run first.jsp?CLIENT=you and the output on your browser is

From Which Page : *first.jsp*
Data From Client : you

The basic difference between getAttribute() and getParameter() is that the first method extracts a (serialized) Java object and the other provides a String value. For both cases a name is given so that its value (be it string or a java bean) can be looked up and extracted.