Java Transformers

There are two methods available for creating a Java-based transformer in SwitchYard:

1. Implement the org.switchyard.transform.Transfomer interface and add a <transform.java> definition to your switchyard.xml.

2. Annotate one or more methods on your Java class with @Transformer.

When using the @Transformer annotation, the SwitchYard maven plugin will automatically generate the <transform.java> definition(s) for you and add them to the switchyard.xml packaged in your application.  The following Java class would produce the <transform.java> definition provided above:

@Named("MyTransformerBean")
public class MyTransformer {
    @Transformer(from = "{urn:switchyard-quickstart-demo:orders:1.0}submitOrder")
    public Order transform(Element from) {
       // handle transformation here
    }
}

The optional from and to elements of the @Transformer annotation can be used to specify the qualified type name used during transformer registration.  If not supplied, the full class name of the method parameter will be used as the from type and the full class name of the return type will be used as the to type.

The CDI bean name specified by @Named annotation is used to resolve transformer class. If you don't specify, then class name of the transformer is used instead like following:

<transforms>
   <transform.java class="org.switchyard.quickstarts.demos.orders.MyTransformer"
                   from="{urn:switchyard-quickstart-demo:orders:1.0}submitOrder"
                   to="java:org.switchyard.quickstarts.demos.orders.Order"/>
</transforms>

Note that both of above <transform.java> definition has a bean attribute or a class attribute. bean attribute and class attribute are mutually exclusive.

JAXB Transformers

The JAXB transformer allows you to perform Java to XML (and XML to Java) transformations using JAXB (XML marshalling and unmarshalling). It is exactly like the JSON Transformer in terms of how it is configured i.e. a to and from configuration with one Java type and one QNamed XML type.

JAXB Java Model Creation

JAXB Java models can be generated from an XML Schema using XJC, or from a WSDL using tools like wsconsume (.sh/.bat), which is shipped with both SwitchYard AS6 and AS7 distros (in the bin directory).

JAXB Transformer Configurations

Working out the available transformations is quite simple. Just look in the ObjectFactory class source file (ObjectFactory.java). In this source file you will see factory methods representing the available marshallings/unmarshallings e.g.

@XmlElementDecl(namespace = "http://com.acme/orders", name = "create")
public JAXBElement<CreateOrder> createOrder(CreateOrder value) {
    return new JAXBElement<Order>(_CreateOrder_QNAME, CreateOrder.class, null, value);
}

JSON Transformers

The JSON transformer provides a basic mapping facility between POJOs and JSON (JSON marshalling and unmarshalling). Just like the JAXB Transformer, specification of the transformer requires a to and from specification with one Java type and one QNamed JSON type, depending on whether you're performing a Java to JSON or JSON to Java transformation.

The following configuration illustrates a JSON to Java transformation.

<trfm:transform.json
            from="{urn:switchyard-quickstart:transform-json:1.0}order"
            to="java:org.switchyard.quickstarts.transform.json.Order"/>

The following configuration illustrates a Java to JSON transformation of the same types as above.

<trfm:transform.json
            from="java:org.switchyard.quickstarts.transform.json.Order"
            to="{urn:switchyard-quickstart:transform-json:1.0}order"/>

Smooks Transformers

There are three distinct transformation models available with Smooks in SwitchYard:

1. XML to Java :  Based on a standard Smooks Java Binding configuration.

2. Java to XML:   Based on a standard Smooks Java Binding configuration.

3. Smooks :  This is a "normal" Smooks transformation in which the developer must define which Smooks filtering Result is to be exported back to the SwitchYard Message as the transformation result.

Smooks transformations are declared by including a <transform.smooks> definition in switchyard.xml.

<transform.smooks config="/smooks/OrderAck_XML.xml"
                  from="java:org.switchyard.quickstarts.transform.smooks.OrderAck"
                  to="{urn:switchyard-quickstart:transform-smooks:1.0}submitOrderResponse"
                  type="JAVA2XML"/>

The config attribute points to a Smooks resource containing the mapping definition.  The type attribute can be one of SMOOKS, XML2JAVA, or JAVA2XML.

XSLT Transformers

The XSLT transformer allows you to perform a transformation between 2 types, using an XSLT. It is configured simply by specifying the to and from QNames, as well as the path to the XSLT to be applied.

<transform.xslt from="{http://acme/}A" to="{http://acme/}B" xsltFile="com/acme/xslt/A2B.xslt"/>