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Clojure DSL for Apache Camel Clojure CI Clojars Project


Camel is an open source integration framework that empowers you to quickly and easily integrate various systems consuming or producing data.

This library adds a thin layer on top of Java Apache Camel and provides a more idiomatic experience of using Apache Camel in the Clojure ecosystem, without changing the original functionality.


Include in your project.clj


(require [clj-camel.core :as c]
         [clj-camel.util :as cu])


Simple route

(c/route-builder (c/from "direct:test")
                 (c/route-id "test-route")
                 (c/set-body (c/constant "test-body"))
                 (c/log "log: ${body}")
                 (c/to "direct:result"))

Filter (original doc)

(c/route-builder (c/from "direct:test")
                 (c/route-id "test-route")
                 (c/to "http://test-http")
                 (c/filter (c/predicate (comp pos? :body))
                           (c/log "Filtered ... ${body}")
                           (c/to "direct:result"))
                 (c/process (fn [_] {:body "after filter"})))

Choice (original doc)

(c/route-builder (c/choice (c/when (c/predicate (comp pos? :body))
                                   (c/log "when 1")
                                   (c/process some-processor))
                           (c/when (c/predicate (comp neg? :body))
                                   (c/log "when 2")
                                   (c/process some-processor))
                             (c/log "otherwise")
                             (c/process some-processor)))
                 (c/log "after choice"))

Split (original doc)

(c/route-builder (c/from "direct:test")
                 (c/route-id "test-route")
                 (c/process processor1)
                 (c/to "http://test-http")
                 (c/split (c/json-path "$.data.*") {:agg-strategy        c/grouped-exchange-strategy
                                                    :streaming           true
                                                    :parallel-processing true}
                          (c/process (fn [_] {}))
                          (c/filter (c/predicate (comp pos? :reserved-today :body))
                                    (c/log "Filtered ... ${body}")
                                    (c/to "direct:result")))
                 (c/process (fn [_] {:body "after"})))

Aggregate (original doc)

(c/route-builder (c/from "direct:test")
                 (c/set-body (c/constant "test"))
                 (c/aggregate (c/constant 1) c/grouped-body-strategy
                              {:completion-size      1000
                               :completion-timeout   1000
                               :completion-predicate (c/predicate (fn [_] true))}
                              (c/to "direct:result"))
                 (c/log "after aggregating"))

Caching (original doc)

(c/route-builder (c/from "direct:test")
                 (c/route-id "test-route")
                 (c/set-body (c/constant "key"))
                 (c/log "key requested: ${body}")
                 (c/memoize (cu/create-jcache-expiration-policy "cache-name" 60)
                            (c/set-body (c/constant "value"))
                            (c/log "Populate cache with ${body}"))
                 (c/log "key value result: ${body}")
                 (c/to "direct:result"))

Throttling (original doc)

(c/route-builder (c/from "direct:test")
                 (c/set-body (c/constant "test"))
                 (c/throttle 20 {:async-delayed      false
                                 :reject-execution   false
                                 :time-period-millis 10000})
                 (c/log "after throttling")
                 (c/to "direct:result"))

Try/Catch/Finally (original doc)

(c/route-builder (c/from "direct:test")
                 (c/route-id "test-route")
                 (c/do-try (c/to "http://test-http")
                           (c/do-catch Exception
                                       (c/log "handle exception")
                                       (c/log "handle exception2"))
                             (c/log "finally")
                             (c/log "finally2")))
                 (c/log "after do-try"))

MDC from headers UOW

The following will populate MDC context with name-of-mdc-field with value of incoming exchange header field name-of-header-field (if incoming exchange has a respective header)

Example of log:

  "message": "example message",
  "mdc": {
    "name-of-mdc-field": "test-value",
    "camel.breadcrumbId": "xxx",
    "camel.routeId": "yyy"
(c/set-customer-uow-with-mdc-from-headers context {"name-of-header-filed" "name-of-mdc-field"})

GCP Pub-sub attributes propagation

Specified pub-sub message attributes will be added to exchange header if exist

(c/set-pubsub-attributes-propagation context {"pubsub-attribute-name" "name-of-header-field"})

Logging Configuration

When configuring your logging appenders, contrary to the Camel documentation, you will need to add clj-camel.core as your logging namespace.

Apache Camel 3.8 -> 3.11 Migration Notes

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