ConstraintViolationException in Java RESTful Webservice - web-services

Question

I'm relatively new to JavaEE and web services, however, I'm using netbeans to generate my client and webservice resources. I have a resource "CustomerData" that represents a mysql database table and a value "rewardsPoints" representing a column in that table, however, I am unable to update the value due to a ConstraintViolationException, specifically:
javax.validation.ConstraintViolationException: Bean Validation constraint(s) violated while executing Automatic Bean Validation on callback event:'preUpdate'. Please refer to embedded ConstraintViolations for details.
I'm not familiar with the 'preUpdate' callback event, is it something I need to override? I can't seem to figure out exactly why this exception is being thrown, but, as I said, i'm very new to web service programming. Here are my classes:
#Stateless
#Path("customers")
public class CustomerDataFacadeREST extends AbstractFacade<CustomerData> {
#PersistenceContext(unitName = "CustomerPortalPU")
private EntityManager em;
public CustomerDataFacadeREST() {
super(CustomerData.class);
}
#PUT
#Path("{id}")
#Consumes({"application/xml", "application/json"})
public void edit(#PathParam("id") Integer id, CustomerData entity) {
super.edit(entity);
}
#GET
#Path("{id}")
#Produces({"application/xml", "application/json"})
public CustomerData find(#PathParam("id") Integer id) {
return super.find(id);
}
#GET
#Path("addPoints/{id}/{amount}")
#Produces({"text/plain"})
public String addPoints(#PathParam("id") Integer id, #PathParam("amount") int amount) {
CustomerData customer = find(id);
customer.getRewardsPoints(customer.getRewardsPoints() + amount);
em.persist(customer);
edit(customer);
return customer.getRewardsPoints();
}
#Override
protected EntityManager getEntityManager() {
return em;
}
}
And the CustomerData entity class:
#Entity
#Table(name = "tbl_customer_data")
#XmlRootElement
public class CustomerData implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Basic(optional = false)
#Column(name = "id")
private Integer id;
#Basic(optional = false)
#NotNull
#Column(name = "rewards_points")
private int rewardsPoints;
public CustomerData(Integer id, int rewardsPoints) {
this.id = id;
this.rewardsPoints = rewardsPoints;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public int getRewardsPoints() {
return rewardsPoints;
}
public void setRewardsPoints(int rewardsPoints) {
this.rewardsPoints = rewardsPoints;
}
}
When I try to access the URI:
http://localhost:8080/CustomerPortal/ws/customers/addPoints/1/5
to add 5 points to user with id 1 i get an HTTP 500 error and in the glassfish logs it says
[2013-11-05T03:28:11.733-0500] [glassfish 4.0] [WARNING] [ejb.system_exception] [javax.enterprise.system.container.ejb.com.sun.ejb.containers] [tid: _ThreadID=21 _ThreadName=http-listener-1(3)] [timeMillis: 1383640091733] [levelValue: 900] [[
EJB5184:A system exception occurred during an invocation on EJB CustomerDataFacadeREST, method: public java.lang.String com.webservice.entities.CustomerDataFacadeREST.addPoints(java.lang.Integer,int)]]
[2013-11-05T03:28:11.741-0500] [glassfish 4.0] [WARNING] [] [javax.enterprise.web] [tid: _ThreadID=21 _ThreadName=http-listener-1(3)] [timeMillis: 1383640091741] [levelValue: 900] [[
StandardWrapperValve[com.webservice.entities.ApplicationConfig]: Servlet.service() for servlet com.webservice.entities.ApplicationConfig threw exception
javax.validation.ConstraintViolationException: Bean Validation constraint(s) violated while executing Automatic Bean Validation on callback event:'preUpdate'. Please refer to embedded ConstraintViolations for details.
Any resources, insight or information regarding this issue would be extremely helpful.

Answer 1

The exception has little to do with web services: it has to do with Bean Validation instead.
In this case, since the Validation fails inside method addPoints (look at the stack trace) the only line that can cause it is when persisting or editing an Entity of type CustomerData. The only constraint you have in that class is that rewardsPoints should not be null. So, that's the cause of the exception.
However there some things that won't work in addPoints method:
You should check that find() method doesn't return a null object.
customer.getRewardsPoints(customer.getRewardsPoints() + amount) never sets the property (does it compile?)
EntityManager.persist() throws exception if the entity already exists. You probably want to remove that line if you only want to edit (update) the entity.
Note: I am not sure that the code you have posted is really compiling and causing that exception. That's probably caused by another version.