DataSonnet

Since Camel 3.7

Camel supports DataSonnet transformations to allow an Expression or Predicate to be used in the DSL.

For example, you could use DataSonnet to create a Predicate in a Message Filter or as an Expression for a Recipient List.

To use a DataSonnet expression use the following Java code:

datasonnet("someDSExpression")

DataSonnet Options

The DataSonnet language supports 5 options, which are listed below.

Name Default Java Type Description

bodyMediaType

String

The String representation of the message’s body MediaType.

outputMediaType

String

The String representation of the MediaType to output.

source

String

Source to use, instead of message body. You can prefix with variable:, header:, or property: to specify kind of source. Otherwise, the source is assumed to be a variable. Use empty or null to use default source, which is the message body.

resultType

String

Sets the class of the result type (type from output).

trim

true

Boolean

Whether to trim the value to remove leading and trailing whitespaces and line breaks.

Example

Here is a simple example using a DataSonnet expression as a predicate in a Message Filter:

// lets route if a line item is over $100
from("queue:foo")
    .filter(datasonnet("ds.arrays.firstWith(body.lineItems, function(item) item > 100) != null"))
    .to("queue:bar")

And the XML DSL:

<route>
    <from uri="queue:foo"/>
    <filter>
        <datasonnet>ds.arrays.firstWith(body.lineItems, function(item) item > 100) != null</datasonnet>
        <to uri="queue:bar"/>
    </filter>
</route>

Here is an example of a simple DataSonnet expression as a transformation EIP. This example will transform an XML body with lineItems into JSON while filtering out lines that are under 100.

from("queue:foo")
    .transform(datasonnet("ds.filter(body.lineItems, function(item) item > 100)", String.class, "application/xml", "application/json"))
    .to("queue:bar")

And the XML DSL:

<route>
    <from uri="queue:foo"/>
    <filter>
        <datasonnet bodyMediaType="application/xml" outputMediaType="application/json" resultTypeName="java.lang.String" >
            ds.filter(body.lineItems, function(item) item > 100)
        </datasonnet>
        <to uri="queue:bar"/>
    </filter>
</route>

Setting result type

The DataSonnet expression will return a com.datasonnet.document.Document by default. The document preserves the content type metadata along with the contents of the result of the transformation. In predicates, however, the Document will be automatically unwrapped and the boolean content will be returned. Similarly any times you want the content in a specific result type like a String. To do this you have to instruct the DataSonnet which result type to return.

In Java DSL:

datasonnet("body.foo", String.class)

In XML DSL you use the resultType attribute to provide a fully qualified classname:

<datasonnet resultType="java.lang.String">body.foo</datasonnet>

If the expression results in an array, or an object, you can instruct the expression to return you List.class or Map.class, respectively. However, you must also set the output media type to application/x-java-object.

The default Document object is useful in situations where there are intermediate transformation steps, and so retaining the content metadata through a route execution is valuable.

Specifying Media Types

Traditionally the input and output media types are specified through the DataSonnet Header The DataSonnet expression provides convenience options for specifying the body and output media types without the need for a Header, this is useful if the transformation is a one-liner, for example.

The DataSonnet expression will look for a body media type in the following order:

  1. If the body is a Document it will use the metadata in the object

  2. If the bodyMediaType parameter was provided in the DSL, it will use its value

  3. A "CamelDatasonnetBodyMediaType" exchange property

  4. A "Content-Type" message header

  5. The DataSonnet Header payload media type directive

  6. application/x-java-object

And for output media type:

  1. If the outputMediaType parameter was provided in the DSL, it will use its value

  2. A "CamelDatasonnetOutputMediaType" exchange property

  3. A "CamelDatasonnetOutputMediaType" message header

  4. The DataSonnet Header output media type directive

  5. application/x-java-object

Functions

Camel adds the following DataSonnet functions that can be used to access the exchange:

Function Argument Type Description

cml.properties

key for property

String

To lookup a property using the Properties component (property placeholders).

cml.header

the header name

String

Will return the message header.

cml.exchangeProperty

key for property

String

Will return the exchange property.

Here’s an example showing some of these functions in use:

from("direct:in")
    .setBody(datasonnet("'hello, ' + cml.properties('toGreet')", String.class))
    .to("mock:camel");

And the XML DSL:

<route>
    <from uri="direct:in"/>
    <setBody>
        <datasonnet resultTypeName="java.lang.String">'hello, ' + cml.properties('toGreet')</datasonnet>
    </setBody>
    <to uri="mock:camel"/>
</route>

Loading script from external resource

You can externalize the script and have Camel load it from a resource such as "classpath:", "file:", or "http:".
This is done using the following syntax: "resource:scheme:location", eg to refer to a file on the classpath you can do:

.setHeader("myHeader").datasonnet("resource:classpath:mydatasonnet.ds")

Dependencies

To use scripting languages in your camel routes you need to add a dependency on camel-datasonnet.

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

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-datasonnet</artifactId>
  <version>x.x.x</version>
</dependency>