Difference between getAttribute and getParameter

Question

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

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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

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Another case when you should use  getParameter   is when forwarding with parameters in jsp    lt jsp forward page  destination jsp  gt       lt jsp param name  userName  value  hamid   gt   lt  jsp forward gt    In destination jsp  you can access userName like this   request getParameter  userName

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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

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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

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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  amp    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

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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  lt    page import  quot java util   quot  import  quot java io   quot   gt   lt   request setAttribute  quot PAGE quot    quot first jsp quot     gt   lt jsp forward page  quot  second jsp quot   gt   and second jsp   lt    page import  quot java util   quot  import  quot java io   quot   gt  From Which Page    lt   request getAttribute  quot PAGE quot    gt  lt br gt  Data From Client    lt   request getParameter  quot CLIENT quot    gt   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

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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

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-getParameter       lt html gt   lt body gt   lt form name  testForm  method  post  action  testJSP jsp  gt   lt input type  text  name  testParam  value  ClientParam  gt   lt input type  submit  gt   lt  form gt   lt  body gt   lt  html gt        lt html gt       lt body gt       lt       String sValue   request getParameter  testParam          gt       lt    sValue   gt       lt  body gt       lt  html gt    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

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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

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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

[java] Difference between getAttribute() and getParameter()

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