I have an enity 'A' which as a collection of enity 'B', the collection is mapped to be lazily loaded which works fine as expected.
Entity 'B' has an one to one relationship with entity 'C' which I have mapped to be lazily loaded by Proxy.But I see that a sql is immediatley executed to fetch enity 'C' whenever the parent enity 'B' is fetched into memory. I guess I am missing some basic concept here, can someone clarify it please.

Not all one-to-one relations can be proxied. For example if, constrained="true" or if you use property-ref, proxies don't work. See http://docs.jboss.org/hibernate/stable/ ... n-onetoone

If the one-to-one is bi-directional it is always so that only one end can be proxied, the other end is always eagerly fetched.

I have my code below, can somebody point out what is exactly causing the one to one mapped entity 'SubscriberServiceConfig ' not to be lazily fetched.
1)Class 'A'

@Entity
@Table(name = "SERVICE")
@org.hibernate.annotations.Entity(dynamicInsert = true, dynamicUpdate = true)
public class Service implements Serializable {
private static final long serialVersionUID = -5345322513746418441L;

@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "EDI_SEQ")
@SequenceGenerator(name = "EDI_SEQ", sequenceName = "EDI_SEQ", allocationSize = 1)
@Column(name = "SERVICE_ID", nullable = false, unique = true)
private Long id;

@OneToMany(mappedBy = "service")
@Cascade( { CascadeType.ALL, CascadeType.DELETE_ORPHAN })
@LazyCollection(LazyCollectionOption.TRUE)
private List<SubscriberServiceReltn> subscrServiceReltns = new ArrayList<SubscriberServiceReltn>();
}

2) Class B
@Entity
@Table(name = "SUBSCRIBER_SERVICE_RELTN")
@org.hibernate.annotations.Entity(dynamicInsert = true, dynamicUpdate = true)
public class SubscriberServiceReltn implements Serializable {

private static final long serialVersionUID = 2843713013040198985L;

@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "EDI_SEQ")
@SequenceGenerator(name = "EDI_SEQ", sequenceName = "EDI_SEQ", allocationSize = 1)
@Column(name = "SUBSCRIBER_SERVICE_RELTN_ID", nullable = false, unique = true)
private Long id;

@ManyToOne(targetEntity = com.cerner.edi.dep.subscriber.entity.Subscriber.class, fetch = FetchType.LAZY)
@JoinColumn(name = "SUBSCRIBER_ID", insertable = true, updatable = false, nullable = false)
private Subscriber subscriber;

@ManyToOne(targetEntity = com.cerner.edi.dep.subscriber.entity.Service.class, fetch = FetchType.LAZY)
@JoinColumn(name = "SERVICE_ID", insertable = true, updatable = false, nullable = false)
private Service service;

@OneToOne(mappedBy = "subscriberServiceReltn", fetch = FetchType.LAZY)
@Cascade( { CascadeType.DELETE_ORPHAN, CascadeType.ALL })
private SubscriberServiceConfig subscriberServiceConfig;
}


c) Class 'C'
@Entity
@Table(name = "SUBSCRIBER_SERVICE_CONFIG")
@org.hibernate.annotations.Entity(dynamicInsert = true, dynamicUpdate = true)
public class SubscriberServiceConfig implements Serializable {

private static final long serialVersionUID = 6351762912651912853L;
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "EDI_SEQ")
@SequenceGenerator(name = "EDI_SEQ", sequenceName = "EDI_SEQ", allocationSize = 1)
@Column(name = "SUBSCRIBER_SERVICE_CONFIG_ID", nullable = false, unique = true)
private Long id;

@OneToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "SUBSCRIBER_SERVICE_RELTN_ID")
private SubscriberServiceReltn subscriberServiceReltn;
}

The presence of the mappedBy attribute is what is causing this. Even with proxies Hibernate needs know if subscriberServiceConfig should be null or not. This information is only found in the SUBSCRIBER_SERVICE_CONFIG table. Eg. is there is a value in the SUBSCRIBER_SERVICE_RELTN_ID column pointing back to the primary key in SUBSCRIBER_SERVICE_RELTN table or not? So, since Hibernate needs to query the table anyway the entity is loaded eagerly.

In the other direction, the lazy fetching works since Hibernate knows if there is an associated entity or not just by looking at the SUBSCRIBER_SERVICE_RELTN_ID column that is already part of the first query.

Now I understand .Thanks for the reply.