Complex DSL extensions

Complex DSL extensions are not complex to use, but they encapsulate enterprise integration patterns that would be anything but trivial to write using plain Camel.

Validation

The validation DSL extension implements a validation process that delegates the actual message validation to a validator, which can be an endpoint or an object that implements validation logic.

If validation succeeds the message is forwarded in-only to the next processor defined in the route, otherwise the message is dropped. In both cases the response generated by the validator is returned to the sender of the original in-out message exchange.

In the following example, the validation process delegates message validation to the direct:validator endpoint. If validation succeeds the message is forwarded as in-only exchange to mock:output, otherwise it is dropped. The response returned from direct:validator is returned to the direct:input endpoint.

    from('direct:input')
        .validation('direct:validator')
        .to('mock:output')

The validation process interprets a message exchange as failed if any of the following conditions is true:

• an exception was thrown by the validator
• the message exchange contains an exception
• the message exchange contains a fault message (i.e. an out message marked as fault)

Instead of providing an endpoint, the validator logic can also be provided as Groovy Closure or as Camel Processor:

    Processor validator = new MyFamousValidator()

    from('direct:input1')
        .validation(validator)
        .to('mock:output')

    from('direct:input2')
        // throw a validation exception
        .validation { throw new ValidationException('input sucks in any case') }
        .to('mock:output')

Multiplast

The Multiplast enterprise integration pattern combines splitter and recipient list EIPs. It generates a list of n messages and a list of n endpoint URIs, sends splitted messages in parallel to their corresponding endpoint, and aggregates their responses.

The DSL element therefore requires three parameters:

• splittingExpression: Camel expression that creates a list of messages from the original one
• recipientListExpression: Camel expression which creates the list of target endpoint URIs
• aggregationStrategy: strategy for aggregating received responses

    from('direct:input')
        .multiplast(splitter, recipients, aggregator)
        .to('mock:output')