Chapter 23. RESTEasy Atom Support

RESTEasy has defined a simple object model in Java to represent Atom and uses Jakarta XML Binding to marshal and unmarshal it. The main classes are in the org.jboss.resteasy.plugins.providers.atom package and are Feed, Entry, Content, and Link. If you look at the source, you will see that these are annotated with Jakarta XML Binding annotations. The distribution contains the javadocs for this project and are a must to learn the model. Here is a simple example of sending an atom feed using the RESTEasy 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("Bill Burke"));
        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;
    }
}

RESTEasy's atom provider is Jakarta XML Binding based, there are no limits to sending atom objects using XML. All the other Jakarta XML Binding providers that RESTEasy has like JSON and fastinfoset can automatically be re-use. Just add "atom+" in front of the main subtype. i.e. @Produces("application/atom+json") or @Consumes("application/atom+fastinfoset")

The org.jboss.resteasy.plugins.providers.atom.Content class is used to unmarshal and marshal Jakarta XML Binding annotated objects that are the body of the content. Here's an 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 tell the content object, an object is being sent back and it is to be marshalled appropriately. If using a different base format than XML, i.e. "application/atom+json", this attached object will be marshalled into that same format.

If the input is an atom document, Jakarta XML Binding objects can be extracted 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);
    }
}