Difference between getAttribute() and getParameter

Question

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

Answer 1

getParameter - Is used for getting the information you need from the Client's HTML page

getAttribute - This is used for getting the parameters set previously in another or the same JSP or Servlet page.

Basically, if you are forwarding or just going from one jsp/servlet to another one, there is no way to have the information you want unless you choose to put them in an Object and use the set-attribute to store in a Session variable.

Using getAttribute, you can retrieve the Session variable.

Answer 2

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");%>
<jsp:forward page="/second.jsp"/>

and second.jsp:

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

Answer 3

• getParameter() returns http request parameters. Those passed from the client to the server. For example http://example.com/servlet?parameter=1. Can only return String

• getAttribute() is for server-side usage only - you fill the request with attributes that you can use within the same request. For example - you set an attribute in a servlet, and read it from a JSP. Can be used for any object, not just string.

Answer 4

It is crucial to know that attributes are not parameters.

The return type for attributes is an Object, whereas the return type for a parameter is a String. When calling the getAttribute(String name) method, bear in mind that the attributes must be cast.

Additionally, there is no servlet specific attributes, and there are no session parameters.

This post is written with the purpose to connect on @Bozho's response, as additional information that can be useful for other people.

Answer 5

from http://www.coderanch.com/t/361868/Servlets/java/request-getParameter-request-getAttribute

A "parameter" is a name/value pair sent from the client to the server - typically, from an HTML form. Parameters can only have String values. Sometimes (e.g. using a GET request) you will see these encoded directly into the URL (after the ?, each in the form name=value, and each pair separated by an &). Other times, they are included in the body of the request, when using methods such as POST.

An "attribute" is a server-local storage mechanism - nothing stored in scoped attribues is ever transmitted outside the server unless you explicitly make that happen. Attributes have String names, but store Object values. Note that attributes are specific to Java (they store Java Objects), while parameters are platform-independent (they are only formatted strings composed of generic bytes).

There are four scopes of attributes in total: "page" (for JSPs and tag files only), "request" (limited to the current client's request, destroyed after request is completed), "session" (stored in the client's session, invalidated after the session is terminated), "application" (exist for all components to access during the entire deployed lifetime of your application).

The bottom line is: use parameters when obtaining data from the client, use scoped attributes when storing objects on the server for use internally by your application only.

Answer 6

-getParameter() :

<html>
<body>
<form name="testForm" method="post" action="testJSP.jsp">
<input type="text" name="testParam" value="ClientParam">
<input type="submit">
</form>
</body>
</html>

    <html>
    <body>
    <%
    String sValue = request.getParameter("testParam");
    %>
    <%= sValue %>
    </body>
    </html>

request.getParameter("testParam") will get the value from the posted form of the input box named "testParam" which is "Client param". It will then print it out, so you should see "Client Param" on the screen. So request.getParameter() will retrieve a value that the client has submitted. You will get the value on the server side.

-getAttribute() : request.getAttribute(), this is all done server side. YOU add the attribute to the request and YOU submit the request to another resource, the client does not know about this. So all the code handling this would typically be in servlets.getAttribute always return object.