//tag::ref-doc[] = Transform Processor Transformer processor allows you to convert the message payload structure based on a SpEL expression. Here is an example of how you can run this application. `java -jar filter-processor-kafka-<version>.jar --spel.function.expression=toUpperCase()` Change kafka to rabbit if you want to run it against RabbitMQ. === Payload The incoming message can contain any type of payload. == Options //tag::configuration-properties[] $$spel.function.expression$$:: $$A SpEL expression to apply.$$ *($$String$$, default: `$$<none>$$`)* //end::configuration-properties[] //end::ref-doc[]