Hi,

Just been playing around with hibernate and i came across this issue which i dont know how to solve.
Any help will be appreciated.

I have a 2 Entities.

Client Entity has collection of Session Entities.

Client.java

public class ClientDO implements Serializable{
@Id
@Column(name="clientID")
@GeneratedValue(strategy=GenerationType.AUTO)
private Integer id;
private String status;
@Column(name="DateOfBirth")
@Temporal(javax.persistence.TemporalType.DATE)
private Date dob;
private String login;
private Integer testerid;
private String type;
private String role;

@OneToMany(cascade=CascadeType.PERSIST,
mappedBy="id",
fetch=FetchType.EAGER)
@JoinColumn(name="clientID",nullable=false)
private Set<SessionDO> sessions;

}

Session.java
@Entity
@Table(name="session")
public class SessionDO implements Serializable {
@Id
@Column(name="sessionID")
@GeneratedValue(strategy=GenerationType.AUTO)
private Integer id;
@ManyToOne(optional=false)
private ClientDO client;
...
}

When I load client object, SQL produced by Hibernate looks like:
select clientdo0_.clientID as clientID0_2_, clientdo0_.status as status0_2_, clientdo0_.DateOfBirth as DateOfBi3_0_2_, clientdo0_.login as login0_2_, clientdo0_.testerid as testerid0_2_, clientdo0_.type as type0_2_, clientdo0_.role as role0_2_, sessions1_.clientID as clientID4_, sessions1_.sessionID as sessionID4_, sessions1_.sessionID as sessionID1_0_, sessions1_.client_clientID as client7_1_0_, sessions1_.status as status1_0_, sessions1_.productId as productId1_0_, sessions1_.suffix as suffix1_0_, sessions1_.hand as hand1_0_, sessions1_.demographicsConfirmed as demograp6_1_0_, clientdo2_.clientID as clientID0_1_, clientdo2_.status as status0_1_, clientdo2_.DateOfBirth as DateOfBi3_0_1_, clientdo2_.login as login0_1_, clientdo2_.testerid as testerid0_1_, clientdo2_.type as type0_1_, clientdo2_.role as role0_1_
from client clientdo0_
left outer join session sessions1_ on clientdo0_.clientID=sessions1_.clientID
left outer join client clientdo2_ on sessions1_.client_clientID=clientdo2_.clientID where clientdo0_.clientID=?

Why is there an extra outer join when only 1 join is needed to fetch the data required. Any idea?

I Think , your mapping is wrong..
Try this...

Client.java

public class ClientDO implements Serializable{
@Id
@Column(name="clientID")
@GeneratedValue(strategy=GenerationType.AUTO)
private Integer id;
private String status;
@Column(name="DateOfBirth")
@Temporal(javax.persistence.TemporalType.DATE)
private Date dob;
private String login;
private Integer testerid;
private String type;
private String role;

@OneToMany(cascade=CascadeType.PERSIST,
mappedBy="client",
fetch=FetchType.EAGER)
private Set<SessionDO> sessions;

}

Session.java
@Entity
@Table(name="session")
public class SessionDO implements Serializable {
@Id
@Column(name="sessionID")
@GeneratedValue(strategy=GenerationType.AUTO)
private Integer id;

@ManyToOne(optional=false)
@JoinColumn(name="clientID",nullable=false)
private ClientDO client;
...
}

Thanks. It was the mapping issue as you pointed out.