Wire Tap

The wire tap pattern, as shown in Figure 19.1, enables you to route a copy of the message to a separate tap location, while the original message is forwarded to the ultimate destination.

Figure 19.1. Wire Tap Pattern

WireTap node

The wireTap node copies the original exchange to a tapped exchange, whose exchange pattern is set to InOnly, because the tapped exchange should be propagated in a oneway style. The tapped exchange is processed in a separate thread, so that it can run concurrently with the main route.

The wireTap supports two different approaches to tapping an exchange:

Tap a copy of the original exchange.
Tap a new exchange instance, enabling you to customize the tapped exchange.

Tap a copy of the original exchange

Using the Java DSL:

from("direct:start")
    .to("log:foo")
    .wireTap("direct:tap")
    .to("mock:result");

Using XML extensions:

<route>
    <from uri="direct:start"/>
    <to uri="log:foo"/>
    <wireTap uri="direct:tap"/>
    <to uri="mock:result"/>
</route>

Tap and modify a copy of the original exchange

Using the Java DSL, Fuse Mediation Router supports using either a processor or an expression to modify a copy of the original exchange. Using a processor gives you full power over how the exchange is populated, because you can set properties, headers and so on. The expression approach can only be used to modify the In message body.

For example, to modify a copy of the original exchange using the processor approach:

from("direct:start")
    .wireTap("direct:foo", new Processor() {
        public void process(Exchange exchange) throws Exception {
            exchange.getIn().setHeader("foo", "bar");
        }
    }).to("mock:result");


from("direct:foo").to("mock:foo");

And to modify a copy of the original exchange using the expression approach:

from("direct:start")
    .wireTap("direct:foo", constant("Bye World"))
    .to("mock:result");

from("direct:foo").to("mock:foo");

Using the Spring XML extensions, you can modify a copy of the original exchange using the processor approach, where the processorRef attribute references a Spring bean with the myProcessor ID:

<route>
    <from uri="direct:start2"/>
    <wireTap uri="direct:foo" processorRef="myProcessor"/>
    <to uri="mock:result"/>
</route>

And to modify a copy of the original exchange using the expression approach:

<route>
    <from uri="direct:start"/>
    <wireTap uri="direct:foo">
        <body><constant>Bye World</constant></body>
    </wireTap>
    <to uri="mock:result"/>
</route>

Tap a new exchange instance

You can define a wiretap with a new exchange instance by setting the copy flag to false (the default is true). In this case, an initially empty exchange is created for the wiretap.

For example, to create a new exchange instance using the processor approach:

from("direct:start")
    .wireTap("direct:foo", false, new Processor() {
        public void process(Exchange exchange) throws Exception {
            exchange.getIn().setBody("Bye World");
            exchange.getIn().setHeader("foo", "bar");
        }
    }).to("mock:result");


from("direct:foo").to("mock:foo");

Where the second wireTap argument sets the copy flag to false, indicating that the original exchange is not copied and an empty exchange is created instead.

To create a new exchange instance using the expression approach:

from("direct:start")
    .wireTap("direct:foo", false, constant("Bye World"))
    .to("mock:result");

from("direct:foo").to("mock:foo");

Using the Spring XML extensions, you can indicate that a new exchange is to be created by setting the wireTap element's copy attribute to false.

To create a new exchange instance using the processor approach, where the processorRef attribute references a Spring bean with the myProcessor ID, as follows:

<route>
    <from uri="direct:start2"/>
    <wireTap uri="direct:foo" processorRef="myProcessor" copy="false"/>
    <to uri="mock:result"/>
</route>

And to create a new exchange instance using the expression approach:

<route>
    <from uri="direct:start"/>
    <wireTap uri="direct:foo" copy="false">
        <body><constant>Bye World</constant></body>
    </wireTap>
    <to uri="mock:result"/>
</route>

Fuse Mediation Router 1.x

The following example shows how to route a request from an input queue:a endpoint to the wire tap location queue:tap it is received by queue:b

Using the Fluent Builders

RouteBuilder builder = new RouteBuilder() {
    public void configure() {
        errorHandler(deadLetterChannel("mock:error"));

        from("seda:a").multicast().to("seda:tap", "seda:b");
    }
};

Using the Spring XML Extensions

<camelContext errorHandlerRef="errorHandler" streamCache="false" id="camel" xmlns="http://camel.apache.org/schema/spring">
    <route>
        <from uri="seda:a"/>
        <multicast>
            <to uri="seda:tap"/>
            <to uri="seda:b"/>
        </multicast>
    </route>
</camelContext>

Comments powered by Disqus

Contents
Search