[[when-eip]]
= When EIP
:docTitle: When
:description: Triggers a route when an expression evaluates to true
:since: 
:supportLevel: Stable

The When EIP is related to http://www.enterpriseintegrationpatterns.com/ContentBasedRouter.html[Content
Based Router] from the xref:enterprise-integration-patterns.adoc[EIP
patterns]

image::eip/ContentBasedRouter.gif[image]

== Options

// eip options: START
The When EIP has no options.
// eip options: END

== Examples

The following example shows how to route a request from an input
*direct:a* endpoint to either *direct:b*, *direct:c* or *direct:d* depending on
the evaluation of various xref:latest@manual:ROOT:predicate.adoc[Predicate] expressions

[source,java]
----
RouteBuilder builder = new RouteBuilder() {
    public void configure() {
        from("direct:a")
            .choice()
                .when(simple("${header.foo} == 'bar'"))
                    .to("direct:b")
                .when(simple("${header.foo} == 'cheese'"))
                    .to("direct:c")
                .otherwise()
                    .to("direct:d");
    }
};
----


And the same example using XML:

[source,xml]
----
<camelContext xmlns="http://camel.apache.org/schema/spring">
    <route>
        <from uri="direct:a"/>
        <choice>
            <when>
                <simple>${header.foo} == 'bar'</simple>
                <to uri="direct:b"/>
            </when>
            <when>
                <simple>${header.foo} == 'cheese'</simple>
                <to uri="direct:c"/>
            </when>
            <otherwise>
                <to uri="direct:d"/>
            </otherwise>
        </choice>
    </route>
</camelContext>
----
