Writing Integrations in YAML

Defining a route

A route is collection of elements defined as follows:

- from: (1)
    uri: "direct:start"
    steps: (2)
      - filter:
          expression:
            simple: "${in.header.continue} == true"
          steps: (2)
            - to:
                uri: "log:filtered"
      - to:
          uri: "log:original"
1 route entry point, by default from and rest are supported
2 processing steps

Each step is represented by a YAML map that has a single entry where the field name is the EIP name

As general rule each step provide all the parameters the related definition declares but there are some minor differences/enhancements:

  • Output Aware Steps

    Some steps such as filter and split have their own pipeline when an exchange matches the filter expression or for the items generated by the split expression, such pipeline can be defined by the steps field:

    filter:
      expression:
        simple: "${in.header.continue} == true"
          steps:
            - to:
                uri: "log:filtered"

    if the steps field is omitted, then each subsequent step is considered part of the filter pipeline.

  • Expression Aware Steps

    Some EIP such as filter and split supports the definition of an expression through the expression field:

    Explicit Expression field
    filter:
        expression:
          simple: "${in.header.continue} == true"

    To make the DSL less verbose, the expression field can be omitted:

    Implicit Expression field
    filter:
        simple: "${in.header.continue} == true"

    In general expression can be defined inline like in the examples above but in case you need provide more information, you can 'unroll' the expression definition and configure any single parameter the expression defines.

    Full Expression definition
    filter:
        tokenize:
          token: "<"
          end-token: ">"
  • Data Format Aware Steps

    Some EIP such as set-body and marshal supports the definition of data formats through the data-format field:

    Explicit Data Format field
    set-body:
        data-format:
          json:
            library: Gson

    To make the DSL less verbose, the data-format field can be omitted:

    Implicit Data Format field
    set-body:
        json:
          library: Gson

    In case you want to use the data-format’s default settings, you need to place an empty block as data format parameters, like json: {}

Defining endpoints

To define an endpoint with the YAML dsl you have three options:

  1. Using a classic Camel URI:

    - from:
        uri: "timer:tick?period=1s"
        steps:
          - to:
              uri: "telegram:bots?authorizationToken=XXX"
  2. Using URI and parameters:

    - from:
        uri: "timer://tick"
        parameters:
          period: "1s"
        steps:
          - to:
              uri: "telegram:bots"
              parameters:
                authorizationToken: "XXX"
  3. Using the YAML implementation of the Endpoint DSL:

    - from:
        timer:
          name: "tick"
          period: "1s"
        steps:
          - telegram:
              type: "bots"
              authorizationToken: "XXX"

Support for the Endpoint DSL with YAML is experimental and subject to changes.

Support for Endpoint DSL auto completion is not yet available.

Defining beans

In addition to the general support for creating beans provided by Camel Main, the YAML DSL provide a convenient syntax to define and configure them:

- beans:
  - name: beanFromMap  (1)
    type: com.acme.MyBean (2)
    properties: (3)
      foo: bar
1 the name of the bean which will be used to bound the instance to the Camel Registry
2 the full qualified class name of the bean
3 the properties of the bean to be set

The properties of the bean can be defined using either a map or properties style as shown in the example below:

- beans:
  # map style
  - name: beanFromMap
    type: com.acme.MyBean
    properties:
      field1: 'f1'
      field2: 'f2'
      nested:
        field1: 'nf1'
        field2: 'nf2'
  # properties style
  - name: beanFromProps
    type: com.acme.MyBean
    properties:
      field1: 'f1_p'
      field2: 'f2_p'
      nested.field1: 'nf1_p'
      nested.field2: 'nf2_p'

The beans elements can only be used as root element

Extending the DSL

The DSL is designed to be easily extended, so you can provide your own step handler which is discovered at runtime using Camel’s factory finder.

Assuming you want to create a step to simplify the creation of a certain type of endpoints then you need:

  • create a service definition entry in META-INF/services/org/apache/camel/k/yaml with content like:

    class=com.acme.converter.MyConverter
  • create the step handler extending org.apache.camel.k.loader.yaml.parser.ProcessorStepParser

    package com.acme.converter.AcmeConverter;
    
    import org.apache.camel.k.loader.yaml.parser.ProcessorStepParser;
    
    public class AcmeConverter
            implements ProcessorStepParser {
        /**
         * @param context contains references to the camel context and the current node as raw JsonNode
         */
        @Override
        public ProcessorDefinition<?> toProcessor(Context context) {
            // decode the raw json node
            Definition definition = context.node(Definition.class);
    
            // create the definition
            ToDefinition to = new ToDefinition();
            to.setUri(String.format("http://%s:%d/fixed/path", definition.host, definition.port));
    
            return to;
        }
    
        /*
         * Define the data
         */
        public static final class Definition {
            public String host;
    
            @JsonSetter(nulls = Nulls.SKIP)
            public Integer port = 8080;
        }
    }

Assuming the entry in the META-INF/services/org/apache/camel/k/yaml is named acme then you can use it from the YAML DSL like:

from:
  uri: "direct:start"
  steps:
    - acme:
        host: acme.com
        port: 8081

Supported EIP

  • Aggregate

  • Bean

  • Choice

  • Circuit Breaker

  • Claim Check

  • Convert Body To

  • Delay

  • Dynamic Router

  • Enrich

  • Filter

  • From

  • Idempotent Consumer

  • Load Balance

  • Log

  • Loop

  • Marshal

  • Multicast

  • Pipeline

  • PollEnrich

  • Process

  • Recipient List

  • Remove Header

  • Remove Headers

  • Remove Property

  • Remove Properties

  • Resequence

  • Rest DSL

  • Rollback

  • Routing Slip

  • Saga

  • Sample

  • Script

  • ServiceCall

  • Set Body

  • Set Exchange Pattern

  • Set Header

  • Set Property

  • Sort

  • Split

  • Step

  • Stop

  • Threads

  • Throttle

  • Throw Exception

  • To

  • To Dynamic

  • Transacted

  • Transform

  • Try Catch Finally

  • Unmarshal

  • Validate

  • Wire Tap

The Try Catch Finally EIP currently only support specifying one do-catch clause.