---
created_at: '2013-11-15T10:54:50.000Z'
title: We have an employee whose last name is Null (2010)
url: http://stackoverflow.com/questions/4456438/how-can-i-pass-the-string-null-through-wsdl-soap-from-actionscript-3-to-a-co?rq=1
author: gojko
points: 67
story_text: ''
comment_text: 
num_comments: 35
story_id: 
story_title: 
story_url: 
parent_id: 
created_at_i: 1384512890
_tags:
- story
- author_gojko
- story_6738743
objectID: '6738743'
year: 2010

---
# 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](http://wonderfl.net/c/dd23/read) 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](https://issues.apache.org/jira/browse/FLEX-33644), the
following is the culprit (see last two tests in my
[fiddle](http://wonderfl.net/c/dd23/read) which verify this):

    var thisIsNotNull:XML = <root>null</root>;
    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](http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/operators.html#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](https://stackoverflow.com/q/1239466/203705).**

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

**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.