Sort

The Sort is a Message Translator from Hohpe and Woolf. It orders the elements of a body array by a sort key expression. The route downstream sees the array in the chosen order.

      - set_body:
          value: [3, 1, 4, 1, 5, 9, 2, 6]
      - sort:
          expression: "${body}"
      - to: "log:sorted?showBody=true&showCorrelationId=true"

The included route fires a timer every second for three ticks. The set_body step sets the body to a JSON array of eight numbers. The sort step orders the array by the ${body} expression, which uses each element itself as the sort key. The to step logs the sorted array. The sort defaults to ascending order. A reverse: true flag produces descending order.

The Sort step reads the body as a JSON array. A non-array body fails with a processor error. The upstream set_body step guarantees that contract for this example. The sort key expression extracts a comparable value from each element. The expression ${body} uses the element itself. The expression ${body.field} extracts a nested field for sorting objects by a property.

The Sort differs from the Splitter. The Sort keeps the body as a single array and reorders it in place. The Splitter decomposes the body into many exchanges. A route that needs both patterns sorts first and then splits per element. The Sort also pairs with the Aggregator. A split-sort-aggregate flow splits a collection, sorts the fragments, then aggregates the results back into one message.

Per ADR-0001, the sort step compiles into a Service<Exchange> step in the Tower middleware pipeline. The sort runs inside the step and the ordered body flows out before the next step runs. The processor contract is documented in camel-processor/CONTEXT.md.

The example source is at examples/sort.