The Ref expression language is really just a way to look up a custom Expression from the Registry. This is particular convenient to use in the XML DSL.
The Ref language is part of camel-core
.
For example, the splitter pattern can reference a custom expression using the Ref language, as follows:
<beans ...> <bean id="myExpression" class="com.mycompany.MyCustomExpression"/> ... <camelContext> <route> <from uri="seda:a"/> <split> <ref>myExpression</ref> <to uri="mock:b"/> </split> </route> </camelContext> </beans>