# Vert.x Camel Bridge

Apache Camel (http://camel.apache.org) is an open source Java framework that focuses on making integration easier and more accessible to developers.

This bridge lets Vert.x applications interact with Camel endpoints:

- the application can send messages to Camel.

- the application can receive message from Camel.

The bridge relies on the Vert.x event bus and associate an event bus address to a Camel endpoint.

Caution | This component is not polyglot as it requires some classes from Camel that can only be used in Java.

## Using vertx-camel-bridge

To use the Vert.x Camel Bridge, add the following dependency to the dependencies section of your build descriptor:

- Maven (in your `pom.xml`):

    <dependency>
      <groupId>io.vertx</groupId>
      <artifactId>vertx-camel-bridge</artifactId>
      <version>3.4.1</version>
    </dependency>

- Gradle (in your `build.gradle` file):

    compile 'io.vertx:vertx-camel-bridge:3.4.1'

## Bridge configuration

Before being used, the bridge needs to be configured and started:

    def camel = new org.apache.camel.impl.DefaultCamelContext()
    io.vertx.camel.CamelBridge.create(vertx, new io.vertx.camel.CamelBridgeOptions(camel).addInboundMapping(io.vertx.camel.InboundMapping.fromCamel("direct:stuff").toVertx("eventbus-address")).addOutboundMapping(io.vertx.camel.OutboundMapping.fromVertx("eventbus-address").toCamel("stream:out"))).start()

The bridge requires a `CamelContext`. It will find the endpoint from the context. The bridge needs to be started before being used. Be aware the the `start` method is asynchronous. You can use `start` to be notified when the bridge has been started.

### Inbound mapping

Inbound mapping associates a Camel endpoint to an event bus address. Messages received on this endpoint are transformed to event bus messages.

    def endpoint = camel.getEndpoint("direct:foo")

    io.vertx.camel.CamelBridge.create(vertx, new io.vertx.camel.CamelBridgeOptions(camel).addInboundMapping(io.vertx.camel.InboundMapping.fromCamel("direct:stuff").toVertx("eventbus-address")).addInboundMapping(io.vertx.camel.InboundMapping.fromCamel(endpoint).toVertx("eventbus-address")).addInboundMapping(io.vertx.camel.InboundMapping.fromCamel(endpoint).toVertx("eventbus-address").withoutHeadersCopy()).addInboundMapping(io.vertx.camel.InboundMapping.fromCamel(endpoint).toVertx("eventbus-address").usePublish()).addInboundMapping(io.vertx.camel.InboundMapping.fromCamel(endpoint).toVertx("eventbus-address").withBodyType(java.lang.String.class)))

The snippet above shows different ways to configure an inbound mapping:

- you can configure the Camel endpoint either using the `Endpoint` object or its uri

- you can disables the header copy (Camel message headers are copied to the event bus message)

- you can uses `publish` instead of `send` to broadcast the message to all event bus consumers

- you can configures the type of the event bus message body. If not set it uses the Camel message payload. If sets, it looks in the Camel context for a converter between the Camel message payload and the desired type.

Note: `org.fusesource.hawtbuf.Buffer` are automatically converted to `Buffer`.

If `send` is used (so not `publish`), and when the Camel exchange expect a reply (In Out exchange), the Vert.x code expect as reply to the sent message. When the reply arrives it is propagated to the exchange:

    Code not translatable

### Outbound mapping

Outbound mapping associates an event bus address to a Camel endpoint. Messages received on this event bus address are transformed to Camel messages and sent to the endpoint.

    def endpoint = camel.getEndpoint("stream:out")

    io.vertx.camel.CamelBridge.create(vertx, new io.vertx.camel.CamelBridgeOptions(camel).addOutboundMapping(io.vertx.camel.OutboundMapping.fromVertx("eventbus-address").toCamel("stream:out")).addOutboundMapping(io.vertx.camel.OutboundMapping.fromVertx("eventbus-address").toCamel(endpoint)).addOutboundMapping(io.vertx.camel.OutboundMapping.fromVertx("eventbus-address").toCamel(endpoint).withoutHeadersCopy()).addOutboundMapping(io.vertx.camel.OutboundMapping.fromVertx("eventbus-address").toCamel(endpoint)))

The snippet above shows different ways to configure an outbound mapping.

You can connect your outbound mapping to a Camel route:

    camel.addRoutes(new org.apache.camel.builder.RouteBuilder())

    def bridge = io.vertx.camel.CamelBridge.create(vertx, new io.vertx.camel.CamelBridgeOptions(camel).addOutboundMapping(io.vertx.camel.OutboundMapping.fromVertx("test").toCamel("direct:start")))

    camel.start()
    bridge.start()

    vertx.eventBus().send("test", "hello", { reply ->
      // Reply from the route (here it's "OK")
    })

If when you send the message on the event bus you register a reply handler, it configures the Camel exchange to expect a response (it uses the request-reply pattern of the EIP). The response is passed in the reply body. If the route fails, you get a reply failure (recipient failure), with the message as cause:

    camel.addRoutes(new org.apache.camel.builder.RouteBuilder())

    def bridge = io.vertx.camel.CamelBridge.create(vertx, new io.vertx.camel.CamelBridgeOptions(camel).addOutboundMapping(io.vertx.camel.OutboundMapping.fromVertx("camel-route").toCamel("direct:my-route")))

    camel.start()
    bridge.start()

    vertx.eventBus().send("camel-route", "hello", { reply ->
      if (reply.succeeded()) {
        def theResponse = reply.result().body()
      } else {
        def theCause = reply.cause()
      }
    })

If the processing you apply is blocking, you must set blocking to `true`. This avoid executing the processing on the event loop thread:

    camel.addRoutes(new org.apache.camel.builder.RouteBuilder())

    def bridge = io.vertx.camel.CamelBridge.create(vertx, new io.vertx.camel.CamelBridgeOptions(camel).addOutboundMapping(io.vertx.camel.OutboundMapping.fromVertx("camel-route").toCamel("direct:my-route").setBlocking(true)))

    camel.start()
    bridge.start()

    vertx.eventBus().send("camel-route", "hello", { reply ->
      if (reply.succeeded()) {
        def theResponse = reply.result().body()
      } else {
        def theCause = reply.cause()
      }
    })

By default it uses the default worker thread pool, this is customizable using the `setWorkerExecutor` method.

## Stopping the bridge

Don’t forget to stop the bridge using the `stop` method. The `stop` method is asynchronous. You can use `stop` to be notified when the bridge has been stopped.