How to pass Null a real surname to a SOAP web service in ActionScript 3

Question

We have an employee whose surname is Null  Our employee lookup application is killed when that last name is used as the search term  which happens to be quite often now   The error received  thanks Fiddler   is    lt soapenv Fault gt      lt faultcode gt soapenv Server userException lt  faultcode gt      lt faultstring gt coldfusion xml rpc CFCInvocationException   coldfusion runtime MissingArgumentException   The SEARCHSTRING parameter to the getFacultyNames function is required but was not passed in   lt  faultstring gt    Cute  huh   The parameter type is string   I am using    WSDL  SOAP  Flex 3 5 ActionScript 3 ColdFusion 8   Note that the error does not occur when calling the webservice as an object from a ColdFusion page

User · Answer

On the xkcd note  the Bobby Tables website has good advice for avoiding the improper interpretation of user data  in this case  the string  Null   in SQL queries in various languages  including ColdFusion   It is not clear from the question that this is the source of the problem  and given the solution noted in a comment to the first answer  embedding the parameters in a structure  it seems likely that it was something else

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Tracking it down   At first I thought this was a coercion bug where null was getting coerced to  null  and a test of  null     null was passing  It s not  I was close  but so very  very wrong  Sorry about that   I ve since done lots of fiddling on wonderfl net and tracing through the code in mx rpc xml    At line 1795 of XMLEncoder  in the 3 5 source   in setValue  all of the XMLEncoding boils down to   currentChild appendChild xmlSpecialCharsFilter Object value       which is essentially the same as   currentChild appendChild  null      This code  according to my original fiddle  returns an empty XML element  But why    Cause   According to commenter Justin Mclean on bug report FLEX-33664  the following is the culprit  see last two tests in my fiddle which verify this    var thisIsNotNull XML    lt root gt null lt  root gt   if thisIsNotNull    null          always branches here  as  thisIsNotNull    null  strangely returns true        despite the fact that thisIsNotNull is a valid instance of type XML     When currentChild appendChild is passed the string  null   it first converts it to a root XML element with text null  and then tests that element against the null literal  This is a weak equality test  so either the XML containing null is coerced to the null type  or the null type is coerced to a root xml element containing the string  null   and the test passes where it arguably should fail  One fix might be to always use strict equality tests when checking XML  or anything  really  for  nullness    Solution The only reasonable workaround I can think of  short of fixing this bug in every damn version of ActionScript  is to test fields for  null  and escape them as CDATA values    CDATA values are the most appropriate way to mutate an entire text value that would otherwise cause encoding decoding problems  Hex encoding  for instance  is meant for individual characters  CDATA values are preferred when you re escaping the entire text of an element  The biggest reason for this is that it maintains human readability

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It s a kludge  but assuming there s a minimum length for SEARCHSTRING  for example 2 characters  substring the SEARCHSTRING parameter at the second character and pass it as two parameters instead  SEARCHSTRING1   Nu   and SEARCHSTRING2   ll     Concatenate them back together when executing the query to the database

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The problem could be in Flex s SOAP encoder  Try extending the SOAP encoder in your Flex application and debug the program to see how the null value is handled    My guess is  it s passed as NaN  Not a Number   This will mess up the SOAP message unmarshalling process sometime  most notably in the JBoss 5 server      I remember extending the SOAP encoder and performing an explicit check on how NaN is handled

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Stringifying a null value in ActionScript will give the string  NULL   My suspicion is that someone has decided that it is  therefore  a good idea to decode the string  NULL  as null  causing the breakage you see here -- probably because they were passing in null objects and getting strings in the database  when they didn t want that  so be sure to check for that kind of bug  too

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doc 180 had the right concept  except he is focused on numbers  whereas the original poster had issues with strings   The solution is to change the mx rpc xml XMLEncoder file  This is line 121       if  content    null          result    content     I looked at Flex 4 5 1 SDK  line numbers may differ in other versions    Basically  the validation fails because  content is null  and therefore your argument is not added to the outgoing SOAP Packet  thus causing the missing parameter error   You have to extend this class to remove the validation   Then there is a big snowball up the chain  modifying SOAPEncoder to use your modified XMLEncoder  and then modifying Operation to use your modified SOAPEncoder  and then moidfying WebService to use your alternate Operation class   I spent a few hours on it  but I need to move on  It ll probably take a day or two   You may be able to just fix the XMLEncoder line and do some monkey patching to use your own class   I ll also add that if you switch to using RemoteObject AMF with ColdFusion  the null is passed without problems     11 16 2013 update   I have one more recent addition to my last comment about RemoteObject AMF  If you are using ColdFusion nbsp 10  then properties with a null value on an object are removed from the server-side object   So  you have to check for the properties existence before accessing it or you will get a runtime error   Check like this    lt cfif  structKeyExists arguments myObject  propertyName   gt    lt  --- no property code --- gt   lt cfelse gt    lt  --- handle property  normally --- gt   lt  cfif gt    This is a change in behavior from ColdFusion nbsp 9  where the null properties would turn into empty strings     Edit 12 6 2013  Since there was a question about how nulls are treated  here is a quick sample application to demonstrate how a string  null  will relate to the reserved word null    lt  xml version  1 0  encoding  utf-8   gt   lt s Application xmlns fx  http   ns adobe com mxml 2009                 xmlns s  library   ns adobe com flex spark                 xmlns mx  library   ns adobe com flex mx  minWidth  955  minHeight  600  initialize  application1 initializeHandler event   gt       lt fx Script gt           lt   CDATA              import mx events FlexEvent               protected function application1 initializeHandler event FlexEvent  void                               var s  String    null                   if s    null                       trace  null string is not equal to null reserved word using the    condition                      else                       trace  null string is equal to null reserved word using the    condition                                       if s    null                       trace  null string is equal to null reserved word using the    condition                      else                       trace  null string is not equal to null reserved word using the    condition                                       if s     null                       trace  null string is equal to null reserved word using the     condition                      else                       trace  null string is not equal to null reserved word using the     condition                                               gt       lt  fx Script gt       lt fx Declarations gt           lt  -- Place non-visual elements  e g   services  value objects  here -- gt       lt  fx Declarations gt   lt  s Application gt    The trace output is      null string is not equal to null reserved word using the    condition      null string is not equal to null reserved word using the    condition      null string is not equal to null reserved word using the     condition

User · Answer

Well  I guess that Flex  implementation of the SOAP Encoder seems to serialize null values incorrectly  Serializing them as a String Null doesn t seem to be a good solution  The formally correct version seems to be to pass a null value as    lt childtag2 xsi nil  true    gt    So the value of  Null  would be nothing else than a valid string  which is exactly what you are looking for   I guess getting this fixed in Apache Flex shouldn t be that hard to get done  I would recommend opening a Jira issue or to contact the guys of the apache-flex mailinglist  However this would only fix the client side  I can t say if ColdFusion will be able to work with null values encoded this way   See also Radu Cotescu s blog post How to send null values in soapUI requests

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Translate all characters into their hex-entity equivalents  In this case  Null would be converted into  amp  4E  amp  75  amp  6C  amp  6C

User · Answer

As a hack  you could consider having a special handling on the client side  converting  Null  string to something that will never occur  for example  XXNULLXX and converting back on the server    It is not pretty  but it may solve the issue for such a boundary case

[apache-flex] How to pass "Null" (a real surname!) to a SOAP web service in ActionScript 3

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