# 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>3.4.2</version>
    </dependency>

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

    compile 'io.vertx:vertx-camel-bridge:3.4.2'

## Bridge configuration

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

    CamelContext camel = new DefaultCamelContext();
    CamelBridge.create(vertx,
        new CamelBridgeOptions(camel)
            .addInboundMapping(InboundMapping.fromCamel("direct:stuff").toVertx("eventbus-address"))
            .addOutboundMapping(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.

    Endpoint endpoint = camel.getEndpoint("direct:foo");

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

    Endpoint endpoint = camel.getEndpoint("direct:stuff");

    CamelBridge bridge = CamelBridge.create(vertx, new CamelBridgeOptions(camel)
        .addInboundMapping(new InboundMapping().setAddress("test-reply").setEndpoint(endpoint)));

    vertx.eventBus().consumer("with-reply", message -> {
      message.reply("How are you ?");
    });

    camel.start();
    bridge.start();

    ProducerTemplate template = camel.createProducerTemplate();
    Future<Object> future = template.asyncRequestBody(endpoint, "hello");
    String response = template.extractFutureBody(future, String.class);

### 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.

    Endpoint endpoint = camel.getEndpoint("stream:out");

    CamelBridge.create(vertx,
        new CamelBridgeOptions(camel)
            .addOutboundMapping(OutboundMapping.fromVertx("eventbus-address").toCamel("stream:out"))
            .addOutboundMapping(OutboundMapping.fromVertx("eventbus-address").toCamel(endpoint))
            .addOutboundMapping(OutboundMapping.fromVertx("eventbus-address").toCamel(endpoint)
                .withoutHeadersCopy())
            .addOutboundMapping(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 RouteBuilder() {
      @Override
      public void configure() throws Exception {
        from("direct:start")
            .transform(constant("OK"));
      }
    });

    CamelBridge bridge = CamelBridge.create(vertx, new CamelBridgeOptions(camel)
        .addOutboundMapping(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 RouteBuilder() {
      @Override
      public void configure() throws Exception {
        from("direct:my-route")
            .to("http://localhost:8080");
      }
    });

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

    camel.start();
    bridge.start();

    vertx.eventBus().send("camel-route", "hello", reply -> {
      if (reply.succeeded()) {
        Object theResponse = reply.result().body();
      } else {
        Throwable 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 RouteBuilder() {
      @Override
      public void configure() throws Exception {
        from("direct:my-route")
          .process(new Processor() {
            @Override
            public void process(Exchange exchange) throws Exception {
              // Do something blocking...
            }
          })
          .to("http://localhost:8080");
      }
    });

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

    camel.start();
    bridge.start();

    vertx.eventBus().send("camel-route", "hello", reply -> {
      if (reply.succeeded()) {
        Object theResponse = reply.result().body();
      } else {
        Throwable 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.

## Exchanging custom object

If you want to send and receive custom objects, you need to register a codec on the event bus:

    vertx.eventBus().registerDefaultCodec(Person.class, codec);