Apache Camel: Message Router

Message Router

The Message Router from the EIP patterns allows you to consume from an input destination, evaluate some predicate then choose the right output destination.

The following example shows how to route a request from an input queue:a endpoint to either queue:b, queue:c or queue:d depending on the evaluation of various Predicate expressions

Using the Fluent Builders

RouteBuilder builder = new RouteBuilder() {
    public void configure() {
        from("seda:a").choice().when(header("foo").isEqualTo("bar")).to("seda:b")
            .when(header("foo").isEqualTo("cheese")).to("seda:c").otherwise().to("seda:d");
    }
};

Using the Spring XML Extensions

<camelContext id="camel" xmlns="http://activemq.apache.org/camel/schema/spring">
  <route>
    <from uri="seda:a"/>
    <choice>
      <when>
        <xpath>$foo = 'bar'</xpath>
        <to uri="seda:b"/>
      </when>
      <when>
        <xpath>$foo = 'cheese'</xpath>
        <to uri="seda:c"/>
      </when>
      <otherwise>
        <to uri="seda:d"/>
      </otherwise>
    </choice>
  </route>
</camelContext>

Choice without otherwise

If you use a choice without adding an otherwise, any unmatched exchanges will be dropped by default. If you prefer to have an exception for an unmatched exchange, you can add a throwFault to the otherwise.

....otherwise().throwFault("No matching when clause found on choice block");

Using This Pattern

If you would like to use this EIP Pattern then please read the Getting Started, you may also find the Architecture useful particularly the description of Endpoint and URIs. Then you could try out some of the Examples first before trying this pattern out.

Message Router

Choice without otherwise

Using This Pattern

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