Missing Elements in HTTP Request - Null or Empty?

Question

I have a HTTP Request javax.servlet.http.HttpServletRequest that is passing in a value to be used in some code being handled in a Java web service using JAX-RS.

Answer 1

If a parameter is not specified at all like so,

http://example.com/context/servlet?x=foo

then it will return null:

String x = request.getParameter("x"); // "foo"
String y = request.getParameter("y"); // null

If a parameter is specified, but does not have a value like so,

http://example.com/context/servlet?x=foo&y

then it will return an empty string:

String x = request.getParameter("x"); // "foo"
String y = request.getParameter("y"); // ""

Makes sense, right?

Answer 2

Tests if a parameter is present in the request

httpServletRequest.getParameter( "Y" ) == null

The following code tests the value of the parameter if it is present

if ( httpServletRequest.getParameter( "Y" ) != null )
{
    String value = httpServletRequest.getParameter( "Y" );

    // Put your test code here.  Include a empty value check
}