Question

I have an entity like this:

@Entity
@XmlRootElement
public class Article {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private com.google.appengine.api.datastore.Key key;
private String content;
private String title;
private Date created; 
private Date lastUpdate;

private boolean isActive;

   /* public getter and setters */
}

Now I have a rest webserivce which returns the articles:

@SuppressWarnings({ "unchecked", "unused" })
@GET
@Path("/{user}")
@Produces({ MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON })
public List<Article> getArtilceListByUser(@PathParam("user") String userName) {

    List<Article> articles = null;
    EntityManager em = EMF.get().createEntityManager();
    try {
        articles = (List<Article>) em.createQuery("SELECT FROM Article WHERE createdBy = :user AND isActive = true")
                    .setParameter("user", userName)
                    .getResultList();
        // lazy load is activated, but em is closed (find a better solution)
        for (Article article : articles) ;

    } finally {
        em.close();
    }

    return articles;
}

The problem is, that the object of com.google.appengine.api.datastore.Key cannot get serialized to json or xml, but I need the id of the articles… So have I to use a long-type for the id or to add an extra field, which wraps the key? Do you have better solutions for this problem?

Answer 1

com.google.appengine.api.datastore.KeyFactory.keyToString

and then

com.google.appengine.api.datastore.KeyFactory.stringToKey

These create and consume “websafe” keys for just this purpose.