RequestDispatcher forward vs HttpServletResponse sendRedirect

Question

What is the conceptual difference between forward   and sendRedirect

User · Answer

Request Dispatcher is an Interface which is used to dispatch the request or response from web resource to the another web resource. It contains mainly two methods.

request.forward(req,res): This method is used forward the request from one web resource to another resource. i.e from one servlet to another servlet or from one web application to another web appliacation.
response.include(req,res): This method is used include the response of one servlet to another servlet

NOTE: BY using Request Dispatcher we can forward or include the request or responses with in the same server.

request.sendRedirect(): BY using this we can forward or include the request or responses across the different servers. In this the client gets a intimation while redirecting the page but in the above process the client will not get intimation

User · Answer

The main important difference between the forward   and sendRedirect   method is that in case of forward    redirect happens   at server end and not visible to client  but in case of   sendRedirect    redirection happens at client end and it s visible to   client

User · Answer

Technically redirect should be used either if we need to transfer control to different domain or to achieve separation of task   For example in the payment application we do the PaymentProcess first and then redirect to displayPaymentInfo  If the client refreshes the browser only the displayPaymentInfo will be done again and PaymentProcess will not be repeated  But if we use forward in this scenario  both PaymentProcess and displayPaymentInfo will be re-executed sequentially  which may result in incosistent data   For other scenarios  forward is efficient to use since as it is faster than sendRedirect

User · Answer

SendRedirect   will search the content between the servers  it is slow because it has to intimate the browser by sending the URL of the content  then browser will create a new request for the content within the same server or in another one    RquestDispatcher is for searching the content within the server i think  its the server side process and it is faster compare to the SendRedirect   method  but the thing is that it will not intimate the browser in which server it is searching the required date or content  neither it will not ask the browser to change the URL in URL tab  so it causes little inconvenience to the user

User · Answer

requestDispatcher - forward   method         When we use the forward method  the request is transferred to another resource within the same server for further processing    In the case of forward  the web container handles all processing internally and the client or browser is not involved    When forward is called on the requestDispatcherobject  we pass the request and response objects  so our old request object is present on the new resource which is going to process our request    Visually  we are not able to see the forwarded address  it is transparent    Using the forward   method is faster than sendRedirect    When we redirect using forward  and we want to use the same data in a new resource  we can use request setAttribute   as we have a request object available          SendRedirect         In case of sendRedirect  the request is transferred to another resource  to a different domain  or to a    different server for further processing    When you use sendRedirect  the container transfers the request to the client or browser  so the URL given inside the sendRedirect method is visible as a new request to the client    In case of sendRedirect call  the old request and response objects are lost because it   s treated as new request by the browser    In the address bar  we are able to see the new redirected address  It   s not transparent    sendRedirect is slower because one extra round trip is required  because a completely new request is created and the old request object is lost  Two browser request are required    But in sendRedirect  if we want to use the same data for a new resource we have to store the data in session or pass along with the URL          Which one is good       Its depends upon the scenario for which method is more useful       If you want control is transfer to new server or context  and it is treated as completely new task  then we go for sendRedirect    Generally  a forward should be used if the operation can be safely repeated upon a browser reload of the web page and will not affect the result    Source

User · Answer

The RequestDispatcher interface allows you to do a server side forward include whereas sendRedirect   does a client side redirect  In a client side redirect  the server will send back an HTTP status code of 302  temporary redirect  which causes the web browser to issue a brand new HTTP GET request for the content at the redirected location  In contrast  when using the RequestDispatcher interface  the include forward to the new resource is handled entirely on the server side

User · Answer

Simply difference between Forward ServletRequest request  ServletResponse response  and sendRedirect String url  is  forward      The forward   method is executed in the server side  The request is transfer to other resource within same server  It does not depend on the client   s request protocol since the forward    method is provided by the servlet container  The request is shared by the target resource  Only one call is consumed in this method  It can be used within server  We cannot see forwarded message  it is transparent  The forward   method is faster than sendRedirect   method  It is declared in RequestDispatcher interface    sendRedirect      The sendRedirect   method is executed in the client side  The request is transfer to other resource to different server   The sendRedirect   method is provided under HTTP so it can be used only with HTTP clients  New request is created for the destination resource  Two request and response calls are consumed  It can be used within and outside the server  We can see redirected address  it is not transparent  The sendRedirect   method is slower because when new request is created old request object is lost   It is declared in HttpServletResponse

User · Answer

Either of these methods may be  better   i e  more suitable  depending on what you want to do   A server-side redirect is faster insofar as you get the data from a different page without making a round trip to the browser  But the URL seen in the browser is still the original address  so you re creating a little inconsistency there   A client-side redirect is more versatile insofar as it can send you to a completely different server  or change the protocol  e g  from HTTP to HTTPS   or both  And the browser is aware of the new URL  But it takes an extra back-and-forth between server and client

User · Answer

In the web development world  the term  quot redirect quot  is  the act of sending the client an empty HTTP response with just a Location header containing the new URL to which the client has to send a brand new GET request  So basically   Client sends a HTTP request to some jsp  Server sends a HTTP response back with Location  other jsp header Client sends a HTTP request to other jsp  this get reflected in browser address bar   Server sends a HTTP response back with content of other jsp   You can track it with the web browser s builtin addon developer toolset  Press F12 in Chrome IE9 Firebug and check the  quot Network quot  section to see it  Exactly the above is achieved by sendRedirect  quot other jsp quot    The RequestDispatcher forward   doesn t send a redirect  Instead  it uses the content of the target page as HTTP response   Client sends a HTTP request to some jsp  Server sends a HTTP response back with content of other jsp   However  as the original HTTP request was to some jsp  the URL in browser address bar remains unchanged  Also  any request attributes set in the controller behind some jsp will be available in other jsp  This does not happen during a redirect because you re basically forcing the client to create a new HTTP request on other jsp  hereby throwing away the original request on some jsp including all of its attribtues   The RequestDispatcher is extremely useful in the MVC paradigm and or when you want to hide JSP s from direct access  You can put JSP s in the  WEB-INF folder and use a Servlet which controls  preprocesses and postprocesses the requests  The JSPs in the  WEB-INF folder are not directly accessible by URL  but the Servlet can access them using RequestDispatcher forward    You can for example have a JSP file in  WEB-INF login jsp and a LoginServlet which is mapped on an url-pattern of  login  When you invoke http   example com context login  then the servlet s doGet   will be invoked  You can do any preprocessing stuff in there and finally forward the request like  request getRequestDispatcher  quot  WEB-INF login jsp quot   forward request  response    When you submit a form  you normally want to use POST   lt form action  quot login quot  method  quot post quot  gt   This way the servlet s doPost   will be invoked and you can do any postprocessing stuff in there  e g  validation  business logic  login the user  etc   If there are any errors  then you normally want to forward the request back to the same page and display the errors there next to the input fields and so on  You can use the RequestDispatcher for this  If a POST is successful  you normally want to redirect the request  so that the request won t be resubmitted when the user refreshes the request  e g  pressing F5 or navigating back in history   User user   userDAO find username  password   if  user    null        request getSession   setAttribute  quot user quot   user      Login user      response sendRedirect  quot home quot       Redirects to http   example com context home after succesful login    else       request setAttribute  quot error quot    quot Unknown login  please try again  quot       Set error      request getRequestDispatcher  quot  WEB-INF login jsp quot   forward request  response      Forward to same page so that you can display error     A redirect thus instructs the client to fire a new GET request on the given URL  Refreshing the request would then only refresh the redirected request and not the initial request  This will avoid  quot double submits quot  and confusion and bad user experiences  This is also called the POST-Redirect-GET pattern  See also   How do servlets work  Instantiation  sessions  shared variables and multithreading doGet and doPost in Servlets How perform validation and display error message in same form in JSP  HttpServletResponse sendRedirect permanent

[jsp] RequestDispatcher.forward() vs HttpServletResponse.sendRedirect()

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