Glassfish - cannot remove entity using JPA - jax-rs

Question

In my exploration of JPA, I have the code below (which I understand should not be used in production). Running my code produces the following error:
java.lang.IllegalStateException:
Exception Description: Cannot use an EntityTransaction while using JTA.
The Resource code is as follows:
#Path("users")
public class UsersAPI {
#Context
UriInfo uriInfo;
#Inject
UserBean accountsBean;
#GET
#Path("deduplicate")
public Response deduplicateDB(){
List<UserProfile> profiles = accountsBean.getAll();
int profilesNum = profiles.size();
for(int i = 0; i < profilesNum; ++i){
for(int k = 0; k < profilesNum; ++k){
if(i != k){ //if it's not the same profile
if(profiles.get(i).getUsername().equals(profiles.get(k).getUsername())){
accountsBean.remove(profiles.get(k));
profiles.remove(k);
}
}
profilesNum = profiles.size();
}
}
return Response.ok().build();
}
}
The code in the ProfilesBean is as follows:
#Local
#Stateless
public class UserBean {
#PersistenceContext
EntityManager eManager;
public void save(UserProfile data){
eManager.merge(data);
}
public void remove(UserProfile data){
eManager.getTransaction().begin();
eManager.remove(data);
eManager.getTransaction().commit();
}
public List<UserProfile> getAll(){
Query q = eManager.createQuery("SELECT profile FROM Users profile");
return (List<UserProfile>)q.getResultList();
}
}
Here is the code for the Entity class:
#Entity(name="Users")
public class UserProfile {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
Long id;
String password;
#Column(unique=true)
String username;
public UserProfile(String username){
setUsername(username);
}
public UserProfile(){
this(null);
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
}
It seems like the error comes from my misusing the platform somehow. How can I fix this code and not misuse the platform in the future?

Answer 1

If you are using JTA as transaction-type in persistence.xml file just leave JTA handles your transactions
public void remove(UserProfile data){
eManager.remove(eManager.merge(data));
}
UPDATE:
In a more clear solution you could use "find", but you need to provide the object id
public void remove(UserProfile data){
UserProfile e = em.find(UserProfile.class, data.getId());
eManager.remove(e);
}