Camel Predicate Example in xml DSL

Like this:

<route>
  <from uri="jms:queue:order"/>
  <choice>
    <when>
       <simple>${header.type} == 'widget'</simple>
       <to uri="bean:widgetOrder"/>
    </when>
    <when>
      <simple>${header.type} == 'wombat'</simple>
      <to uri="bean:wombatOrder"/>
    </when>
    <otherwise>
      <to uri="bean:miscOrder"/>
    </otherwise>
  </choice>
</route>

The required simple element (see accepted answer) is

<simple>${header.type} == 'widget'</simple>

Notice how the field expression is surrounded by ${} followed by OGNL syntax for comparison, which is not part of the field expression itself.