Using if-else in JSP

Question

I m using the following code to print the name of the user on the browser    lt body gt     lt form gt       lt h1 gt Hello  I m duke  What s you name  lt  h1 gt       lt input type  text  name  user  gt  lt br gt  lt br gt       lt input type  submit  value  submit  gt  amp nbsp  amp nbsp  amp nbsp  amp nbsp       lt input type  reset  gt     lt  form gt     lt  String user request getParameter  user      gt     lt  if user    null    user length      0       out print  I see  You don t have a name   well   Hello no name               else    gt         lt    include file  response jsp    gt      lt       gt     lt  body gt    response jsp    lt body gt       lt h1 gt Hello lt  h1 gt       lt    request getParameter  user     gt   body gt    Every time I execute it  the message     I see  You don t have a name   well   Hello no name   gets displayed even though I haven t entered anything in the textbox  However if I enter anything in it  then the response jsp code is displayed  but I don t want the first message to be displayed on execution  How do I make that happen  Please suggest changes in my code   P S  I had read in some questions that instead of checking for equality with null  one must check it for not equals  so that it doesn t throw null pointer exception  when I tried the same  i e  if user    null  amp  amp       I got NullPointerException

User · Answer

You may try this example    x000D   x000D   lt form gt  x000D     lt h1 gt Hello  I m duke  What s you name  lt  h1 gt  x000D     lt input type  text  name  user  gt  x000D     lt br gt  x000D     lt br gt  x000D     lt input type  submit  value  submit  gt  amp nbsp  amp nbsp  amp nbsp  amp nbsp  x000D     lt input type  reset  gt  x000D   lt  form gt  x000D   lt h1 gt Hello   param user  lt  h1 gt   x000D   lt  -- its Expression Language -- gt  x000D   x000D   x000D

User · Answer

Instead of if-else condition use if in both conditions  it will work that way but not sure why

User · Answer

It s almost always advisable to not use scriptlets in your JSP   They re considered bad form   Instead  try using JSTL  JSP Standard Tag Library  combined with EL  Expression Language  to run the conditional logic you re trying to do   As an added benefit  JSTL also includes other important features like looping   Instead of    lt  String user request getParameter  user      gt   lt  if user    null    user length      0       out print  I see  You don t have a name   well   Hello no name         else    gt       lt    include file  response jsp    gt   lt       gt    Use    lt c choose gt       lt c when test    empty user   gt          I see   You don t have a name   well   Hello no name      lt  c when gt       lt c otherwise gt           lt    include file  response jsp    gt       lt  c otherwise gt   lt  c choose gt    Also  unless you plan on using response jsp somewhere else in your code  it might be easier to just include the html in your otherwise statement    lt c otherwise gt       lt h1 gt Hello lt  h1 gt        user   lt  c otherwise gt    Also of note   To use the core tag  you must import it as follows     lt    taglib uri  http   java sun com jsp jstl core  prefix  c    gt    You want to make it so the user will receive a message when the user submits a username   The easiest way to do this is to not print a message at all when the  user  param is null   You can do some validation to give an error message when the user submits null   This is a more standard approach to your problem   To accomplish this   In scriptlet    lt   String user   request getParameter  user       if  user    null  amp  amp  user length    gt  0             lt    include file  response jsp    gt         gt    In jstl    lt c if test    not empty user   gt       lt    include file  response jsp    gt   lt  c if gt

[jsp] Using if-else in JSP

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