Passing ArrayList from servlet to JSP

Question

I am trying to pass ArrayList which contains object from servlet to JSP  But   Servlet file   request setAttribute  servletName   categoryList     categorylist is an arraylist      contains object of class category   getServletConfig   getServletContext   getRequestDispatcher   GetCategory jsp   forward request response     JSP file     category class      lt   Category category   new Category      creating arraylist object of type category class ArrayList lt Category gt  list   ArrayList lt Category gt       storing passed value from jsp list   request getAttribute  servletName     for int i   0  i  lt  list size    i       category   list get i    out println  category getId      out println category getName      out println category getMainCategoryId          gt

User · Answer

the possible errors would be    1 you set the array list from the servelt in the session  not the in the request  2 the array you set is null  3 you redirect the page instead of forward it   also you should not initialize the list and the category  in jsp  try this    for Category cx    ArrayList lt Category gt  request getAttribute  servletName        out println  cx getId      out println cx getName      out println cx getMainCategoryId

User · Answer

request getAttribute  servletName   method will return Object that you need to cast to ArrayList  ArrayList lt Category gt  list  new ArrayList lt Category gt       storing passed value from jsp list    ArrayList lt Category gt  request getAttribute  servletName

User · Answer

public class myActorServlet extends HttpServlet        private static final long serialVersionUID   1L      private String name      private String user      private String pass      private String given table      private String tid      private String firstname      private String lastname      private String action        Override     public void doPost HttpServletRequest request              HttpServletResponse response              throws IOException  ServletException            response setContentType  text html                connecting to database         Connection con   null          Statement stmt   null          ResultSet rs   null           PrintWriter out   response getWriter            name   request getParameter  screenName            user   request getParameter  username            pass   request getParameter  password            tid   request getParameter  tid            firstname   request getParameter  firstname            lastname   request getParameter  lastname            action   request getParameter  action            given table   request getParameter  tableName             out println   lt html gt             out println   lt head gt             out println   lt title gt Servlet JDBC lt  title gt             out println   lt link rel   stylesheet   type   text css   href   style css   gt             out println   lt  head gt             out println   lt body gt             out println   lt h1 gt Hello      name      lt  h1 gt             out println   lt h1 gt Servlet JDBC lt  h1 gt                                                   init connection object         String sqlSelect    SELECT   FROM      given table                String sqlInsert    INSERT INTO      given table       firstName    lastName   VALUES       firstname            lastname                 String sqlUpdate    UPDATE      given table      SET  firstName       firstname       lastName       lastname      WHERE  id      tid               String sqlDelete    DELETE FROM      given table      WHERE  id         tid                                                                                    out println                    lt p gt Reading Table Data   Pass to JSP File   Okay lt p gt              ArrayList lt Actor gt  list   new ArrayList lt Actor gt                connecting to database         try               Class forName  com mysql jdbc Driver                con   DriverManager getConnection  jdbc mysql   localhost 3306 javabase   user  pass               stmt   con createStatement                rs   stmt executeQuery sqlSelect                  displaying records              while  rs next                      Actor actor   new Actor                    actor setId rs getInt  id                     actor setLastname rs getString  lastname                     actor setFirstname rs getString  firstname                     list add actor                             request setAttribute  actors   list               RequestDispatcher view   request getRequestDispatcher  myActors 1 jsp                view forward request  response              catch  SQLException e                throw new ServletException  Servlet Could not display records    e             catch  ClassNotFoundException e                throw new ServletException  JDBC Driver not found    e             finally               try                   if  rs    null                        rs close                        rs   null                                    if  stmt    null                        stmt close                        stmt   null                                    if  con    null                        con close                        con   null                                  catch  SQLException e                                    out println   lt  body gt  lt  html gt              out close

User · Answer

here list attribute name set in request request setAttribute  List  list   and ArrayList list new ArrayList       lt    ArrayList lt Category gt  a  ArrayList lt Category gt  request getAttribute  List     out print a    for int i 0 i lt a size   i           out println a get i           gt

User · Answer

lt html gt       lt            ArrayList lt Actor gt  list   new ArrayList lt Actor gt             list    ArrayList lt Actor gt   request getAttribute  actors          gt   lt head gt       lt link rel  stylesheet  type  text css  href  style css  gt       lt meta http-equiv  Content-Type  content  text html  charset UTF-8  gt       lt title gt Actor lt  title gt   lt  head gt    lt body gt        lt h2 gt This is Actor Class lt  h2 gt       lt table gt           lt thead gt               lt tr gt                   lt th gt Id lt  th gt                   lt th gt First Name lt  th gt                   lt th gt Last Name lt  th gt               lt  tr gt           lt  thead gt           lt tbody gt               lt   for int i   0  i  lt  list size    i                      Actor actor   new Actor                    actor   list get i                     out println actor getId                       out println actor getFirstname                       out println actor getLastname                   gt                 lt tr gt                   lt td gt  lt   actor getId    gt  lt  td gt                   lt td gt  lt   actor getFirstname    gt  lt  td gt                   lt td gt  lt   actor getLastname    gt  lt  td gt                  lt  tr gt               lt                                gt           lt  tbody gt       lt  table gt    lt  body gt

User · Answer

In the servlet code  with the instruction request setAttribute  servletName   categoryList   you save your list in the request object  and use the name  servletName  for refering it  By the way  using then name  servletName  for a list is quite confusing  maybe it s better call it  list  or something similar   request setAttribute  list   categoryList  Anyway  suppose you don t change your serlvet code  and store the list using the name  servletName   When you arrive to your JSP  it s necessary to retrieve the list from the request  and for that you just need the request getAttribute      method    lt        retrieve your list from the request  with casting  ArrayList lt Category gt  list    ArrayList lt Category gt   request getAttribute  servletName        print the information about every category of the list for Category category   list        out println category getId         out println category getName         out println category getMainCategoryId         gt

[java] Passing ArrayList from servlet to JSP

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