XMPP header enricher - Chat thread id
Expression
SpEL (Spring Expression Language) expression that computes the value.
Example: "payload.toUpperCase() + '_US' "
See also: <a href="http://static.springsource.org/spring/docs/3.0.x/reference/expressions.html" target="_blank>SpEL documentation
Overwrite
Boolean value to indicate whether this header value should overwrite an existing header value for the same name.
Default is 'false'.