Struts 1.1 validation.xml: myList.size() == 0. How to check for this

I have a situation where a list of JobTitles can have 0 length, and if it does, the field jobTitleId should not be validated.

<field property="jobTitleId" depends="validwhen">
    <msg name="required" key="errors.required" />
    <arg position="0" key="fld.job.title" />
    <var>
        <var-name&g开发者_如何学Pythont;test</var-name>
        <var-value>((jobTitles.size() == 0) or (*this* != null))</var-value>
    </var>
</field>

Any help would certainly be appreciated. I've tried the developer docs and I'm just not getting it.

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Apparently the .size() was causing the trouble, so I changed the code so that jobTitles would be null in that case and it worked.