JAX-RS using exception mappers

Question

I have read that I can create an implementation of javax.ws.rs.ext.ExceptionMapper that will map a thrown application exception to a Response object.

I've created a simple example which throws an exception if the phone length is greater than 20 characters when persisting the object. I am expecting the exception to be mapped to an HTTP 400 (Bad Request) response; however, I am receiving an HTTP 500 (Internal Server Error) with the following exception:

java.lang.ClassCastException: com.example.exception.InvalidDataException cannot be cast to java.lang.Error 

What am I missing? Any advice is greatly appreciated.

Exception mapper:

@Provider public class InvalidDataMapper implements ExceptionMapper<InvalidDataException> {      @Override     public Response toResponse(InvalidDataException arg0) {         return Response.status(Response.Status.BAD_REQUEST).build();     }  } 

Exception class:

public class InvalidDataException extends Exception {      private static final long serialVersionUID = 1L;      public InvalidDataException(String message) {         super(message);     }      ...  } 

Entity class:

@Entity @Table(name="PERSON") @XmlAccessorType(XmlAccessType.FIELD) @XmlRootElement public class Person {      @Id @GeneratedValue(strategy = GenerationType.IDENTITY)     @Column(name="ID")     private Long id;      @Column(name="NAME")     private String name;      @Column(name="PHONE")     private String phone;      public Long getId() {         return id;     }      public void setId(Long id) {         this.id = id;     }      public String getName() {         return name;     }      public void setName(String name) {         this.name = name;     }      public String getPhone() {         return phone;     }      public void setPhone(String phone) {         this.phone = phone;     }         @PrePersist     public void validate() throws InvalidDataException {         if (phone != null) {             if (phone.length() > 20) {                 throw new InvalidDataException("Phone number too long: " + phone);             }         }            } } 

Service:

@Path("persons/") @Produces(MediaType.APPLICATION_XML) @Consumes(MediaType.APPLICATION_XML) @Stateless public class PersonResource {      @Context     private UriInfo uriInfo;      @PersistenceContext(name="simple")     private EntityManager em;      @POST     public Response createPerson(JAXBElement<Person> personJaxb) {         Person person = personJaxb.getValue();         em.persist(person);         em.flush();         URI personUri = uriInfo.getAbsolutePathBuilder().         path(person.getId().toString()).build();         return Response.created(personUri).build();       }  } 

Answer 1

Is InvalidDataException getting wrapped in a PersistenceException? Maybe you could do something like the following:

@Provider  public class PersistenceMapper implements ExceptionMapper<PersistenceException> {       @Override      public Response toResponse(PersistenceException arg0) {          if(arg0.getCause() instanceof InvalidDataException) {            return Response.status(Response.Status.BAD_REQUEST).build();          } else {            ...         }     }   }