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15.14. RESTEasy Atom Support

15.14.1. About the Atom API and Provider

The RESTEasy Atom API and Provider is a simple object model that RESTEasy defines to represent Atom. The main classes for the API are in the org.jboss.resteasy.plugins.providers.atom package. RESTEasy uses JAXB to marshal and unmarshal the API. The provider is JAXB based, and is not limited to sending atom objects using XML. All JAXB providers that RESTEasy has can be reused by the Atom API and provider, including JSON. Refer to the javadocs available from the Customer Service Portal for more information on the API.
import org.jboss.resteasy.plugins.providers.atom.Content;
import org.jboss.resteasy.plugins.providers.atom.Entry;
import org.jboss.resteasy.plugins.providers.atom.Feed;
import org.jboss.resteasy.plugins.providers.atom.Link;
import org.jboss.resteasy.plugins.providers.atom.Person;

@Path("atom")
public class MyAtomService
{

   @GET
   @Path("feed")
   @Produces("application/atom+xml")
   public Feed getFeed() throws URISyntaxException
   {
      Feed feed = new Feed();
      feed.setId(new URI("http://example.com/42"));
      feed.setTitle("My Feed");
      feed.setUpdated(new Date());
      Link link = new Link();
      link.setHref(new URI("http://localhost"));
      link.setRel("edit");
      feed.getLinks().add(link);
      feed.getAuthors().add(new Person("John Brown"));
      Entry entry = new Entry();
      entry.setTitle("Hello World");
      Content content = new Content();
      content.setType(MediaType.TEXT_HTML_TYPE);
      content.setText("Nothing much");
      entry.setContent(content);
      feed.getEntries().add(entry);
      return feed;
   }
}

15.14.2. Using JAXB with Atom Provider

The org.jboss.resteasy.plugins.providers.atom.Content class allows you to unmarshal and marshal JAXB annotated objects that are the body of the content. You can refer the example of sending an Entry with a Customer object attached as the body of the entry's content.
 
@XmlRootElement(namespace = "http://jboss.org/Customer")
@XmlAccessorType(XmlAccessType.FIELD)
public class Customer
{
   @XmlElement
   private String name;

   public Customer()
   {
   }

   public Customer(String name)
   {
      this.name = name;
   }

   public String getName()
   {
      return name;
   }
}

@Path("atom")
public static class AtomServer
{
   @GET
   @Path("entry")
   @Produces("application/atom+xml")
   public Entry getEntry()
   {
      Entry entry = new Entry();
      entry.setTitle("Hello World");
      Content content = new Content();
      content.setJAXBObject(new Customer("bill"));
      entry.setContent(content);
      return entry;
   }
}
The Content.setJAXBObject() method is used to specify the content object you are sending back to Java JAXB object to marshal appropriately. If you are using a different base format other than XML, i.e. "application/atom+json", the attached JAXB object is marshalled in the same format. If you have an atom document as your input, you can also extract JAXB objects from Content using the Content.getJAXBObject(Class clazz) method. Here is an example of an input atom document and extracting a Customer object from the content.
 
@Path("atom")
public static class AtomServer
{
   @PUT
   @Path("entry")
   @Produces("application/atom+xml")
   public void putCustomer(Entry entry)
   {
      Content content = entry.getContent();
      Customer cust = content.getJAXBObject(Customer.class);
   }
}