YAML DSL

Since Camel 3.9

The YAML DSL provides the capability to define your Camel routes, route templates & REST DSL configuration 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 a general rule, each step provides 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 a pipeline can be defined by the steps field:
```
filter:
  expression:
    simple: "${in.header.continue} == true"
      steps:
        - to:
            uri: "log:filtered"
```
Expression Aware Steps

Some EIPs such as filter and split support 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 to 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

The EIP marshal and unmarshal supports the definition of data formats:
```
marshal:
    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 two options:

Using a classic Camel URI:

- from:
    uri: "timer:tick?period=1s"
    steps:
      - to:
          uri: "telegram:bots?authorizationToken=XXX"

Using URI and parameters:

- from:
    uri: "timer://tick"
    parameters:
      period: "1s"
    steps:
      - to:
          uri: "telegram:bots"
          parameters:
            authorizationToken: "XXX"

Defining beans

In addition to the general support for creating beans provided by Camel Main, the YAML DSL provides 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 the root element

Configuring options on languages

Some Languages have additional configurations you may need to use.

For example, the JSONPath can be configured to ignore JSon parsing errors. This is intended when you use a Content Based Router and want to route the message to different endpoints. But the JSon payload of the message can be in different forms; meaning that the JSonPath expressions in some cases would fail with an exception, and other times not. In this situation, you need to set suppress-exception to true, as shown below:

- from:
    uri: "direct:start"
    steps:
      - choice:
          when:
          - jsonpath:
              expression: "person.middlename"
              suppress-exceptions: true
            steps:
            - to: "mock:middle"
          - jsonpath:
              expression: "person.lastname"
              suppress-exceptions: true
            steps:
            - to: "mock:last"
          otherwise:
            steps:
              - to: "mock:other"

In the route above, the following message

{
  "person": {
    "firstname": "John",
    "lastname": "Doe"
  }
}

Would have failed the JSonPath expression person.middlename because the JSon payload does not have a middlename field. To remedy this we have suppressed the exception.

External examples

You can find a set of examples using main-yaml in Camel Examples which demonstrate creating Camel Routes with YAML.

Another way to find examples of YAML DSL is to look in Camel Kamelets where each Kamelet is defined using YAML.

Supported EIPs

The following set of high level EIPs are supported in the yaml DSL language. For full details on their expected configuration, please refer to the Camel YAML DSL specification.

Aggregate
Bean
Do Catch
Do Try
Do Finally
Choice
Circuit Breaker
Claim Check
Convert Body To
Delay
Dynamic Router
Enrich
Error Handler
Filter
From
Idempotent Consumer
Intercept
Intercept From
Intercept Send To Endpoint
Load Balance
Log
Loop
Marshal
Multicast
On Completion
On Exception
On Fallback
Otherwise
Pausable
Pipeline
Policy
Poll Enrich
Process
Recipient List
Remove Header
Remove Headers
Remove Property
Remove Properties
Resequence
Resumable
REST DSL
Rollback
Routing Slip
Saga
Sample
Script
Service Call
Set Body
Set Exchange Pattern
Set Header
Set Property
Sort
Split
Step
Stop
Threads
Throttle
Throw Exception
To
To Dynamic
Transacted
Transform
Unmarshal
Validate
When
When Skip Send To Endpoint
Wire Tap

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