What does request getParameter return

Question

index jsp   lt form method  post  action  backend jsp  gt   lt input type  text  name  one    gt   lt input type  submit value  Submit    gt   lt  form gt    In backend jsp what does request getParameter  one    return   request getParameter  one   getClass   getName      returns java lang String  so it must be a String right    However I cannot do  String one   request getParameter  one    if      equals one        or  if  one    null       This is obvious  because variable one does not return null  Is  if  one length    gt  0       only way to go  or are there better solutions or a better approach  I am considering both solutions to be on jsp  Using a servlet  although jsp is a servlet  is a different use case in this scenario

User · Answer

Both if  one length    gt  0     and if      equals one      will check against an empty foo parameter  and an empty parameter is what you d get if the the form is submitted with no value in the foo text field   If there s any chance you can use the Expression Language to handle the parameter  you could access it with empty param foo in an expression    lt c if test    not empty param foo   gt      This page code gets rendered   lt  c if gt

User · Answer

Per the Javadoc      Returns the value of a request parameter as a String  or null if the   parameter does not exist    Do note that it is possible to submit an empty parameter - such that the parameter exists  but has no value   For example  I could include  amp log  amp somethingElse into the URL to enable logging  without needing to specify  amp log true   In this case  the value will be an empty String

User · Answer

String onevalue     if request getParameterMap   containsKey  one    false     onevalue request getParameter  one   toString

[java] What does request.getParameter return?

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