If you do not want to hard-code your file upload servlet with the @MultipartConfig annotation but would rather add it to your <servlet> configuration element in web.xml, following is the syntax (add this as a child element of <servlet>):
<multipart-config>
<location>/tmp</location>
<max-file-size>20848820</max-file-size>
<max-request-size>418018841</max-request-size>
<file-size-threshold>1048576</file-size-threshold>
</multipart-config>