JAX-RS custom mapping from entities to xml

Question

Here's my problem:

Say I have two entities annotated with JAX-RS annotations:

@XmlRootElement
@Entity
public Person {
  private String firstname;
  private String lastname;

  private Address address;
}

@XmlType
@Entity
public Address {
  private String street;
  private String city;
}

This will get rendered into:

<person>
  <firstname></firstname>
  <lastname></lastname>
  <address>
    <street></street>
   <city></city>
  </address>
</person>

My question therefore is:

Is it possible to annotate those entities so that the xml returned is:

<person>
  <firstname></firstname>
  <lastname></lastname>
  <street></street>
  <city></city>
</person>

i.e. properties of Address entity are treated as Person properties (without the enclosing tags)?

Answer 1

I'm not entirely sure why you would want to, but this might work (untested)

@XmlRootElement
@Entity
@XmlAccessorType(XmlAccessType.PROPERTY)
public Person {
   private String firstname;
   private String lastname;

   private Address address;

   // getter and setter for firstname/lastname

   @XmlTransient
   public Address getAddress() { return address; }

   public String getStreet() { return getAddress().getStreet(); }

   // more getters and setters
}

@XmlType
@Entity
public Address {
  private String street;
  private String city;

  // getters and setters
}

I personally would be using a DTO pattern at this point though. Mixing ORM and Serialization annotations is rarely a good thing.

Answer 2

You could do this using EclipseLink JAXB (MOXy). MOXy contains an annotation called @XmlPath, this is used to do XPath based mappings. The self XPath (".") will give you the desired effect:

@Entity 
@XmlAccessorType(XmlAccessType.PROPERTY) 
@XmlRootElement 
public Person { 
   private String firstname; 
   private String lastname; 
   private Address address; 

   // getter and setter for firstname/lastname 

   @XmlPath(".")
   public Address getAddress() { return address; } 

   public String getStreet() { return getAddress().getStreet(); } 

   // more getters and setters 
} 

For an example on using EclipseLink JAXB extensions see:

• http://bdoughan.blogspot.com/2010/07/xpath-based-mapping.html
• http://wiki.eclipse.org/EclipseLink/Examples/MOXy/GettingStarted/MOXyExtensions

In order to use MOXy as your JAXB implementation you must add a jaxb.properties file in with your model classes with the following content:

javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory

BTW, MOXy also has a number of extensions for handling JPA entities:

• http://wiki.eclipse.org/EclipseLink/Examples/MOXy/JPA

I have posted a series of examples to my blog on how to create a JPA based RESTful service using JAX-RS:

• Part 1 - Data Model
• Part 2 - JPA
• Part 3 - JAXB (using MOXy)
• Part 4 - RESTful Service (using an EJB session bean)