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  1. #1
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    Question Testing Value of QueryString

    Hello,

    I'm trying to get the full URL of a webpage and am running into a problem testing the query string. Here's my code so far:

    Code:
    String requestURL = request.getRequestURL().toString();
    String queryString = request.getQueryString();
    
    <%= requestURL %>+<%= queryString %>
    
    if (queryString.equals("")) {
       out.println("is null"); 
    } else {
    	out.println("not null");
    This code works fine so long as there is a query string; if not I get a runtime error on the IF statement. I tried changing queryString definition to request.getQueryString().toString; - but it also fails if there's no queryString.

    Perhaps a better question is, how do I properly test for null

    Thanks

  • #2
    God Emperor Fou-Lu's Avatar
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    I don't do JSP at all, but you cannot compare queryString.equals if request.getQueryString returns null (this would be common in just regular java of course, but I don't remember if it applies at the JSP level as well). So if the request.getQueryString() can return null, then you simply check that as well: if (querystring != null) instead of .equals(""). If its not null, then you can then check the .equals("") to see if its empty if desired in the else block.

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    billatl (09-27-2012)

  • #3
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    Yea, that work. I'd originally tried if (queryString = null) { but was getting a String vs. Boolean mismatch. Hadn't thought of using not instead.

    Thanks

  • #4
    God Emperor Fou-Lu's Avatar
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    Quote Originally Posted by billatl View Post
    Yea, that work. I'd originally tried if (queryString = null) { but was getting a String vs. Boolean mismatch. Hadn't thought of using not instead.

    Thanks
    This happens since the result of a string assignment is the value of the string, not a boolean result (even if the value of the string is null, that would then be equatable to if ((stringvar = null) == null)). What would work is if (querystring == null), as that would return true if it is null and false otherwise.


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