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44.2. How to Implement a Component

Overview

This section gives a brief overview of the steps required to implement a custom Apache Camel component.

Which interfaces do you need to implement?

When implementing a component, it is usually necessary to implement the following Java interfaces:
  • org.apache.camel.Component
  • org.apache.camel.Endpoint
  • org.apache.camel.Consumer
  • org.apache.camel.Producer
In addition, it can also be necessary to implement the following Java interfaces:
  • org.apache.camel.Exchange
  • org.apache.camel.Message

Implementation steps

You typically implement a custom component as follows:
  1. Implement the Component interface—A component object acts as an endpoint factory. You extend the DefaultComponent class and implement the createEndpoint() method.
    See Chapter 45, Component Interface.
  2. Implement the Endpoint interface—An endpoint represents a resource identified by a specific URI. The approach taken when implementing an endpoint depends on whether the consumers follow an event-driven pattern, a scheduled poll pattern, or a polling pattern.
    For an event-driven pattern, implement the endpoint by extending the DefaultEndpoint class and implementing the following methods:
    • createProducer()
    • createConsumer()
    For a scheduled poll pattern, implement the endpoint by extending the ScheduledPollEndpoint class and implementing the following methods:
    • createProducer()
    • createConsumer()
    For a polling pattern, implement the endpoint by extending the DefaultPollingEndpoint class and implementing the following methods:
    • createProducer()
    • createPollConsumer()
    See Chapter 46, Endpoint Interface.
  3. Implement the Consumer interface—There are several different approaches you can take to implementing a consumer, depending on which pattern you need to implement (event-driven, scheduled poll, or polling). The consumer implementation is also crucially important for determining the threading model used for processing a message exchange.
    See Section 47.2, “Implementing the Consumer Interface”.
  4. Implement the Producer interface—To implement a producer, you extend the DefaultProducer class and implement the process() method.
    See Chapter 48, Producer Interface.
  5. Optionally implement the Exchange or the Message interface—The default implementations of Exchange and Message can be used directly, but occasionally, you might find it necessary to customize these types.
    See Chapter 49, Exchange Interface and Chapter 50, Message Interface.

Installing and configuring the component

You can install a custom component in one of the following ways:
  • Add the component directly to the CamelContext—The CamelContext.addComponent() method adds a component programatically.
  • Add the component using Spring configuration—The standard Spring bean element creates a component instance. The bean's id attribute implicitly defines the component prefix. For details, see Section 44.3.2, “Configuring a Component”.
  • Configure Apache Camel to auto-discover the component—Auto-discovery, ensures that Apache Camel automatically loads the component on demand. For details, see Section 44.3.1, “Setting Up Auto-Discovery”.