Hi. Can anybody explain me, why i get dublicate Objects (same instanzes) from the resultList of an namedQuery and Joint Fetch?
I have a Object Person with a list of Phones. If the personA has 2 phones, i execute the namedQuery with fetch join and get the correct count of 2 Rows (outer join) from the Database. My resultset has now 2 items of the same persons. But i have only one person with 2 phones. The problem seams the Join. I think, the Query should identify the same objects (to call hashCode or equals) and should only get one item back.
Example:
Code:
create table person
(
person_id bigint not null AUTO_INCREMENT,
firstname varchar(50),
primary key (person_id)
) engine=innodb default charset=utf8 ;
create table phone
(
phone_id bigint not null AUTO_INCREMENT,
phonenumber varchar(25),
person_id bigint not null,
primary key (phone_id)
) engine=innodb default charset=utf8 ;
alter table phone add constraint phone_person_fk foreign key (person_id) references person (person_id);
Code:
@Table(name="phone")
public class Phone {
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="phone_id")
private Long phoneId;
@Column(name="phonenumber")
private String phoneNumber;
public long getPhoneId() {return phoneId;}
public void setPhoneId(long phoneId) {this.phoneId = phoneId;}
public String getPhoneNumber() {return phoneNumber;}
public void setPhoneNumber(String phoneNumber) {this.phoneNumber = phoneNumber;}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((phoneId == null) ? 0 : phoneId.hashCode());
result = prime * result
+ ((phoneNumber == null) ? 0 : phoneNumber.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Phone other = (Phone) obj;
if (phoneId == null) {
if (other.phoneId != null)
return false;
} else if (!phoneId.equals(other.phoneId))
return false;
if (phoneNumber == null) {
if (other.phoneNumber != null)
return false;
} else if (!phoneNumber.equals(other.phoneNumber))
return false;
return true;
}
Code:
@Entity
@Table(name="person")
@NamedQueries( { @NamedQuery(name = "person.loadAll", query = "SELECT p FROM Person p LEFT JOIN FETCH p.phoneList") })
public class Person {
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="person_id")
private Long personId;
@Column(name="firstname")
private String firstName;
@OneToMany(cascade=CascadeType.ALL)
@JoinColumn(name="person_id")
private List<Phone> phoneList;
public Long getPersonId() {return personId;}
public void setPersonId(Long personId) {this.personId = personId;}
public String getFirstName() {return firstName;}
public void setFirstName(String firstName) {this.firstName = firstName; }
public List<Phone> getPhoneList() {return phoneList;}
public void setPhoneList(List<Phone> phoneList) {this.phoneList = phoneList;}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result
+ ((firstName == null) ? 0 : firstName.hashCode());
result = prime * result
+ ((personId == null) ? 0 : personId.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Person other = (Person) obj;
if (firstName == null) {
if (other.firstName != null)
return false;
} else if (!firstName.equals(other.firstName))
return false;
if (personId == null) {
if (other.personId != null)
return false;
} else if (!personId.equals(other.personId))
return false;
return true;
}
I persist one person with 2 phones sucessesfully. Inside table person exist one row with personid 1;
Inside table phone exists two rows with phoneid 1 and 2 and both with personid 1.
Code:
Person person = new Person();
person.setFirstName("jon");
Phone phone1 = new Phone();
phone1.setPhoneNumber("020-020222");
Phone phone2 = new Phone();
phone2.setPhoneNumber("0178-2221020222");
List<Phone> phoneList = new ArrayList();
phoneList.add(phone1);
phoneList.add(phone2);
person.setPhoneList(phoneList);
em.persist(person);
After this, i will load the person with phoneList
with only one sql (named query with left outer join).
Code:
Query q = em.createNamedQuery("person.loadAll");
Collection<Person> c = (List<Person>)q.getResultList();
The resulting sql (correct) gets 2 rows.
Code:
select
person0_.person_id as person1_1_0_,
phonelist1_.phone_id as phone1_7_1_,
person0_.firstname as firstname1_0_,
phonelist1_.phonenumber as phonenum2_7_1_,
phonelist1_.person_id as person3_0__,
phonelist1_.phone_id as phone1_0__
from
person person0_
left outer join
phone phonelist1_
on person0_.person_id=phonelist1_.person_id
The List c now has 2 same Objects inside! I think, it should be only one person. Whats wrong? Thanks for every tip. alex
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