32.7. Predicates

Basic predicates

You can use xpath in the Java DSL or the XML DSL in a context where a predicate is expected—for example, as the argument to a filter() processor or as the argument to a when() clause.
For example, the following route filters incoming messages, allowing a message to pass, only if the /person/city element contains the value, London: 
from("direct:tie")
    .filter().xpath("/person/city = 'London'").to("file:target/messages/uk");
The following route evaluates the XPath predicate in a when() clause: 
from("direct:tie")
    .choice()
        .when(xpath("/person/city = 'London'")).to("file:target/messages/uk")
        .otherwise().to("file:target/messages/others");

XPath predicate operators

The XPath language supports the standard XPath predicate operators, as shown in Table 32.2, “Operators for the XPath Language”.

Table 32.2. Operators for the XPath Language

OperatorDescription
=Equals.
!=Not equal to.
>Greater than.
>=Greater than or equals.
<Less than.
<=Less than or equals.
orCombine two predicates with logical and.
andCombine two predicates with logical inclusive or.
not()Negate predicate argument.