12.14. RESTEasy JAXB

12.14.1. Create a JAXB Decorator

Summary

RESTEasy's JAXB providers have a pluggable way to decorate Marshaller and Unmarshaller instances. An annotation is created that can trigger either a Marshaller or Unmarshaller instance. This topic covers the steps to create a JAXB decorator with RESTEasy.

Procedure 12.8. Create a JAXB Decorator with RESTEasy

  1. Create the Processor Class

    1. Create a class that implements DecoratorProcessor<Target, Annotation>. The target is either the JAXB Marshaller or Unmarshaller class. The annotation is created in step two.
    2. Annotate the class with @DecorateTypes, and declare the MIME Types the decorator should decorate.
    3. Set properties or values within the decorate function.

    Example 12.22. Example Processor Class

    import org.jboss.resteasy.core.interception.DecoratorProcessor;
    import org.jboss.resteasy.annotations.DecorateTypes;
    
    import javax.xml.bind.Marshaller;
    import javax.xml.bind.PropertyException;
    import javax.ws.rs.core.MediaType;
    import javax.ws.rs.Produces;
    import java.lang.annotation.Annotation;
    
    @DecorateTypes({"text/*+xml", "application/*+xml"})
    public class PrettyProcessor implements DecoratorProcessor<Marshaller, Pretty>
    {
        public Marshaller decorate(Marshaller target, Pretty annotation,
    	  Class type, Annotation[] annotations, MediaType mediaType)
        {
    	target.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
        }
    }
    
    
  2. Create the Annotation

    1. Create a custom interface that is annotated with the @Decorator annotation.
    2. Declare the processor and target for the @Decorator annotation. The processor is created in step one. The target is either the JAXB Marshaller or Unmarshaller class.

    Example 12.23. Example Annotation

    import org.jboss.resteasy.annotations.Decorator;
    
    @Target({ElementType.TYPE, ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD})
    @Retention(RetentionPolicy.RUNTIME)
    @Decorator(processor = PrettyProcessor.class, target = Marshaller.class)
    public @interface Pretty {}
    
    
  3. Add the annotation created in step two to a function so that either the input or output is decorated when it is marshalled.
Result

The JAXB decorator has been created and applied within the JAX-RS web service.