when null!=null (jsp)


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Thread: when null!=null (jsp)

  1. #1
    Join Date
    May 2006
    Posts
    1

    when null!=null (jsp)

    hello all,

    having a little trouble today... i can't test for null correctly. some code:

    <%
    String thisString = null;
    String thisString_sent = request.getParameter("thisString");

    if (thisString_sent!=null)
    out.print("::"+thisString_sent);


    %>

    <form method="post" action="#">
    <input type="button" onclick="form.submit();" value="<%=thisString_sent%>">
    <input type="hidden" name="thisString" id="thisString" value="<%=thisString_sent%>">
    </form>

    so... request.getParameter("thisString") should receive null from post data and it does as you can see by the button value. so, why does it even enter the if statement? any ideas?

    thanks!
    newb

  2. #2
    Join Date
    Feb 2006
    Location
    Cologne - Germany
    Posts
    271
    <input type="hidden" name="thisString" id="thisString" value="<%=thisString_sent%>">
    if thisString_sent is null, this will place the string "null" at this place.
    why don't you just let the jsp print out the value of thisString_sent to debug?

  3. #3
    Join Date
    May 2006
    Posts
    23
    I have run into that same problem you are having using the Tomcat ServletEngine (3 or 4 times this week infact). I don't know if this is a bug in tomcat's newest release or what. The problem as I have experienced it is that for some reason, using the != null operand in a jsp tag does not work the way it should. My work around was to use if == null { do nothing... } else { do what I need to do. That seems to work just fine.
    Last edited by smcneill; 05-03-2006 at 09:29 AM.

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