Transformer

Transformer (org.apache.camel.spi.Transformer) performs declarative transformation of the message according to the declared Input Type and/or Output Type on a route definition which declares the expected message type. The default camel Message implements DataTypeAware, which allows to hold the message type represented by DataType.

If the input type and/or output type is declared by Input Type and/or Output Type in the route definition, and it is different from actual message type at runtime, camel internal processor looks for a Transformer which transforms from the current message type to the expected message type and apply. Once transform succeed or message is already in expected type, then the message data type is updated.

Data type format

scheme:name

where scheme is the type of data model like java, xml or json, and name is the individual data type name. If you only specify scheme then it hits all the data types which has that scheme like a wildcard.

Supported Transformers

Transformer Description

Data Format Transformer

Transform with using Data Format

Endpoint Transformer

Transform with using Endpoint

Custom Transformer

Transform with using custom transformer class. Transformer must be a subclass of org.apache.camel.spi.Transformer

Common Options

All transformers have following common options to specify which data type is supported by the transformer. scheme or both of fromType and toType must be specified.

Name Description

scheme

Type of data model like xml or json. For example if xml is specified, the transformer is applied for all java -> xml and xml -> java transformation.

fromType

Data type to transform from.

toType

Data type to transform to.

DataFormat Transformer Options

Name Description

type

Data Format type

ref

reference to the Data Format ID

Here is an example to specify Bindy DataFormat type:

Java DSL:

BindyDataFormat bindy = new BindyDataFormat();
bindy.setType(BindyType.Csv);
bindy.setClassType(com.example.Order.class);
transformer()
    .fromType(com.example.Order.class)
    .toType("csv:CSVOrder")
    .withDataFormat(bindy);

XML DSL:

<dataFormatTransformer fromType="java:com.example.Order" toType="csv:CSVOrder">
    <bindy id="csvdf" type="Csv" classType="com.example.Order"/>
</dataFormatTransformer>

Endpoint Transformer Options

Name Description

ref

Reference to the Endpoint ID

uri

Endpoint URI

Here is an example to specify endpoint URI in Java DSL:

transformer()
    .fromType("xml")
    .toType("json")
    .withUri("dozer:myDozer?mappingFile=myMapping.xml...");

And here is an example to specify endpoint ref in XML DSL:

<endpointTransformer ref="myDozerEndpoint" fromType="xml" toType="json"/>

Custom Transformer Options

Note that Transformer must be a subclass of org.apache.camel.spi.Transformer

Name Description

ref

Reference to the custom Transformer bean ID

className

Fully qualified class name of the custom Transformer class

Here is an example to specify custom Transformer class:

Java DSL:

transformer()
    .fromType("xml")
    .toType("json")
    .withJava(com.example.MyCustomTransformer.class);

XML DSL:

<customTransformer className="com.example.MyCustomTransformer" fromType="xml" toType="json"/>

Example

For example to declare the Endpoint Transformer which uses xslt component to transform from xml:ABCOrder to xml:XYZOrder, we can do as follows:

Java DSL:

transformer()
    .fromType("xml:ABCOrder")
    .toType("xml:XYZOrder")
    .withUri("xslt:transform.xsl");

XML DSL:

<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
    <transformers>
        <endpointTransformer uri="xslt:transform.xsl" fromType="xml:ABCOrder" toType="xml:XYZOrder"/>
    </transformers>
    ....
</camelContext>

If you have following route definition, above transformer will be applied when direct:abc endpoint sends the message to direct:xyz:

Java DSL:

from("direct:abc")
    .inputType("xml:ABCOrder")
    .to("direct:xyz");

from("direct:xyz")
    .inputType("xml:XYZOrder")
    .to("somewhere:else");

XML DSL:

<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
    <route>
        <from uri="direct:abc"/>
        <inputType urn="xml:ABCOrder"/>
        <to uri="direct:xyz"/>
    </route>
    <route>
        <from uri="direct:xyz"/>
        <inputType urn="xml:XYZOrder"/>
        <to uri="somewhere:else"/>
    </route>
</camelContext>

See Also

The Validator is a related functionality.

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