java lang IllegalStateException Cannot forward sendRedirect create session after response has been committed

Question

This method throws      java lang IllegalStateException  Cannot forward after response has been committed   and I am unable to spot the problem  Any help       int noOfRows   Integer parseInt request getParameter  noOfRows         String chkboxVal              String FormatId null      Vector vRow   new Vector        Vector vRow1   new Vector        String GroupId           String GroupDesc           for  int i   0  i  lt  noOfRows  i              if   request getParameter  chk select    i      null                chkboxVal    notticked             else               chkboxVal   request getParameter  chk select    i               if  chkboxVal equals  ticked                      fwdurl    true                   Statement st1   con createStatement                    GroupId   request getParameter  GroupId    i                   GroupDesc   request getParameter  GroupDesc    i                   ResultSet rs1   st1                          executeQuery  select FileId Description from cs2k Files                                       where FileId like  M   and co code                                       ccode                   ResultSetMetaData rsm   rs1 getMetaData                    int cCount   rsm getColumnCount                     while  rs1 next                          Vector vCol1   new Vector                        for  int j   1  j  lt   cCount  j                              vCol1 addElement rs1 getObject j                                              vRow addElement vCol1                                     rs1   st1                          executeQuery  select FileId NotAllowed from cs2kGroupSub                                       where FileId like  M   and GroupId                                        GroupId           and co code       ccode                   rsm   rs1 getMetaData                    cCount   rsm getColumnCount                     while  rs1 next                          Vector vCol2   new Vector                        for  int j   1  j  lt   cCount  j                              vCol2 addElement rs1 getObject j                                              vRow1 addElement vCol2                                         throw new Exception  test                     break                                    if  fwdurl equals  true                 throw new Exception  test               response sendRedirect  cs2k GroupCopiedUpdt jsp             request setAttribute  GroupId   GroupId           request setAttribute  GroupDesc   GroupDesc           request setAttribute  vRow   vRow           request setAttribute  vRow1   vRow1           getServletConfig   getServletContext   getRequestDispatcher                    GroupCopiedUpdt jsp   forward request  response

User · Answer

This is because your servlet is trying to access a request object which is no more exist.. A servlet's forward or include statement does not stop execution of method block. It continues to the end of method block or first return statement just like any other java method.

The best way to resolve this problem just set the page (where you suppose to forward the request) dynamically according your logic. That is:

protected void doPost(request , response){
String returnPage="default.jsp";
if(condition1){
 returnPage="page1.jsp";
}
if(condition2){
   returnPage="page2.jsp";
}
request.getRequestDispatcher(returnPage).forward(request,response); //at last line
}

and do the forward only once at last line...

you can also fix this problem using return statement after each forward() or put each forward() in if...else block

User · Answer

A common misunderstanding among starters is that they think that the call of a forward    sendRedirect    or sendError   would magically exit and  quot jump quot  out of the method block  hereby ignoring the remnant of the code  For example  protected void doXxx         if  someCondition            sendRedirect              forward       This is STILL invoked when someCondition is true     This is thus actually not true  They do certainly not behave differently than any other Java methods  expect of System exit   of course   When the someCondition in above example is true and you re thus calling forward   after sendRedirect   or sendError   on the same request response  then the chance is big that you will get the exception   java lang IllegalStateException  Cannot forward after response has been committed  If the if statement calls a forward   and you re afterwards calling sendRedirect   or sendError    then below exception will be thrown   java lang IllegalStateException  Cannot call sendRedirect   after the response has been committed  To fix this  you need either to add a return  statement afterwards protected void doXxx         if  someCondition            sendRedirect            return            forward           or to introduce an else block  protected void doXxx         if  someCondition            sendRedirect          else           forward             To naildown the root cause in your code  just search for any line which calls a forward    sendRedirect   or sendError   without exiting the method block or skipping the remnant of the code  This can be inside the same servlet before the particular code line  but also in any servlet or filter which was been called before the particular servlet  In case of sendError    if your sole purpose is to set the response status  use setStatus   instead   Another probable cause is that the servlet writes to the response while a forward   will be called  or has been called in the very same method  protected void doXxx         out write  quot some string quot                    forward       Fail     The response buffer size defaults in most server to 2KB  so if you write more than 2KB to it  then it will be committed and forward   will fail the same way   java lang IllegalStateException  Cannot forward after response has been committed  Solution is obvious  just don t write to the response in the servlet  That s the responsibility of the JSP  You just set a request attribute like so request setAttribute  quot data quot    quot some string quot   and then print it in JSP like so   data   See also our Servlets wiki page to learn how to use Servlets the right way   Another probable cause is that the servlet writes a file download to the response after which e g  a forward   is called  protected void doXxx         out write bytes                   forward       Fail     This is technically not possible  You need to remove the forward   call  The enduser will stay on the currently opened page  If you actually intend to change the page after a file download  then you need to move the file download logic to page load of the target page   Yet another probable cause is that the forward    sendRedirect   or sendError   methods are invoked via Java code embedded in a JSP file in form of old fashioned way  lt   scriptlets   gt   a practice which was officially discouraged since 2001  For example   lt  DOCTYPE html gt   lt html lang  quot en quot  gt       lt head gt                    lt  head gt       lt body gt                        lt   sendRedirect      gt                            lt  body gt   lt  html gt   The problem here is that JSP internally immediately writes template text  i e  HTML code  via out write  quot  lt  DOCTYPE html gt      etc     quot   as soon as it s encountered  This is thus essentially the same problem as explained in previous section  Solution is obvious  just don t write Java code in a JSP file  That s the responsibility of a normal Java class such as a Servlet or a Filter  See also our Servlets wiki page to learn how to use Servlets the right way   See also   What exactly does  quot Response already committed quot  mean  How to handle exceptions then    Unrelated to your concrete problem  your JDBC code is leaking resources  Fix that as well  For hints  see also How often should Connection  Statement and ResultSet be closed in JDBC

User · Answer

even adding a return statement brings up this exception  for which only solution is this code   if  response isCommitted       Place another redirection

User · Answer

I removed           super service req  res     Then it worked fine for me

User · Answer

Bump     I just had the same error  I noticed that I was invoking super doPost request  response   when overriding the doPost   method as well as explicitly invoking the superclass constructor       public ScheduleServlet             super               TODO Auto-generated constructor stub         As soon as I commented out the super doPost request  response   from within doPost   statement it worked perfectly     protected void doPost HttpServletRequest request  HttpServletResponse response  throws ServletException  IOException              super doPost request  response              More code here         Needless to say  I need to re-read on super   best practices  p

User · Answer

You should add return statement while you are forwarding or redirecting the flow   Example     if forwardind       request getRequestDispatcher   abs jsp   forward request  response       return    if redirecting       response sendRedirect roundTripURI       return

User · Answer

Typically you see this error after you have already done a redirect and then try to output some more data to the output stream  In the cases where I have seen this in the past  it is often one of the filters that is trying to redirect the page  and then still forwards through to the servlet  I cannot see anything immediately wrong with the servlet  so you might want to try having a look at any filters that you have in place as well   Edit  Some more help in diagnosing the problem     The first step to diagnosing this problem is to ascertain exactly where the exception is being thrown  We are assuming that it is being thrown by the line  getServletConfig   getServletContext                      getRequestDispatcher   GroupCopiedUpdt jsp                      forward request  response     But you might find that it is being thrown later in the code  where you are trying to output to the output stream after you have tried to do the forward  If it is coming from the above line  then it means that somewhere before this line you have either    output data to the output stream  or done another redirect beforehand    Good luck

User · Answer

After return forward method you can simply do this   return null    It will break the current scope

[servlets] java.lang.IllegalStateException: Cannot (forward | sendRedirect | create session) after response has been committed

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