yaml-snakeyaml-dataformat.adoc

YAML

YAML is a Data Format to marshal and unmarshal Java objects to and from YAML.

For YAML to object marshalling, Camel provides integration with three popular YAML libraries:

• The SnakeYAML library

Every library requires adding the special camel component (see "Dependency…​" paragraphs further down). By default Camel uses the SnakeYAML library.

YAML Options

The YAML SnakeYAML dataformat supports 10 options which are listed below.

{% raw %}

Name	Default	Java Type	Description
library	SnakeYAML	YAMLLibrary	Which yaml library to use such. Is by default SnakeYAML
unmarshalTypeName		String	Class name of the java type to use when unarmshalling
constructor		String	BaseConstructor to construct incoming documents.
representer		String	Representer to emit outgoing objects.
dumperOptions		String	DumperOptions to configure outgoing objects.
resolver		String	Resolver to detect implicit type
useApplicationContextClassLoader	true	Boolean	Use ApplicationContextClassLoader as custom ClassLoader
prettyFlow	false	Boolean	Force the emitter to produce a pretty YAML document when using the flow style.
allowAnyType	false	Boolean	Allow any class to be un-marshaled
typeFilter		List	Set the types SnakeYAML is allowed to un-marshall

{% endraw %}

Warning

SnakeYAML can load any class from YAML definition which may lead to security breach so by default, SnakeYAML DataForma restrict the object it can load to standard Java objects like List or Long. If you want to load custom POJOs you need to add theirs type to SnakeYAML DataFormat type filter list. If your source is trusted, you can set the property allowAnyType to true so SnakeYAML DataForma won’t perform any filter on the types.

Using YAML data format with the SnakeYAML library

• Turn Object messages into yaml then send to MQSeries

  from("activemq:My.Queue")
    .marshal().yaml()
    .to("mqseries:Another.Queue");

  from("activemq:My.Queue")
    .marshal().yaml(YAMLLibrary.SnakeYAML)
    .to("mqseries:Another.Queue");

• Restrict classes to be loaded from YAML

  // Creat a SnakeYAMLDataFormat instance
  SnakeYAMLDataFormat yaml = new SnakeYAMLDataFormat();
  
  // Restrict classes to be loaded from YAML
  yaml.addTypeFilters(TypeFilters.types(MyPojo.class, MyOtherPojo.class));
  
  from("activemq:My.Queue")
    .unmarshal(yaml)
    .to("mqseries:Another.Queue");

Using YAML in Spring DSL

When using Data Format in Spring DSL you need to declare the data formats first. This is done in the DataFormats XML tag.

<dataFormats>
  <!--
    here we define a YAML data format with the id snake and that it should use
    the TestPojo as the class type when doing unmarshal. The unmarshalTypeName
    is optional
  -->
  <yaml
    id="snake"
    library="SnakeYAML"
    unmarshalTypeName="org.apache.camel.component.yaml.model.TestPojo"/>

  <!--
    here we define a YAML data format with the id snake-safe which restricts the
    classes to be loaded from YAML to TestPojo and those belonging to package
    com.mycompany
  -->
  <yaml id="snake-safe">
    <typeFilter value="org.apache.camel.component.yaml.model.TestPojo"/>
    <typeFilter value="com.mycompany\..*" type="regexp"/>
  </yaml>
</dataFormats>

And then you can refer to those ids in the route:

  <route>
    <from uri="direct:unmarshal"/>
    <unmarshal>
      <custom ref="snake"/>
    </unmarshal>
    <to uri="mock:unmarshal"/>
  </route>
  <route>
    <from uri="direct:unmarshal-safe"/>
    <unmarshal>
      <custom ref="snake-safe"/>
    </unmarshal>
    <to uri="mock:unmarshal-safe"/>
  </route>

Dependencies for SnakeYAML

To use YAML in your camel routes you need to add the a dependency on camel-snakeyaml which implements this data format.

If you use maven you could just add the following to your pom.xml, substituting the version number for the latest & greatest release (see the download page for the latest versions).

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-snakeyaml</artifactId>
  <version>${camel-version}</version>
</dependency>