@Entity @Table(name = "master")
public class Master implements java.io.Serializable {
  @Id @Column(name = "ID", unique = true, nullable = false, precision = 9, scale = 0)
  private int id;
  @OneToOne(fetch = FetchType.LAZY, mappedBy = "master")
  private Detail detail;
  public Master() { }
  public int getId() {
    return id;
  }
  public void setId(int id) {
    this.id = id;
  }
  public Detail getDetail() {
    return detail;
  }
  public void setDetail(Detail detail) {
    this.detail = detail;
  }
}

@Entity @Table(name = "detail")
public class Detail implements java.io.Serializable {
  @Id @Column(name = "ID", unique = true, nullable = false, precision = 9, scale = 0)
  private int id;
  @ManyToOne(fetch = FetchType.LAZY, optional = false)   
  @JoinColumn(name = "master_id")
  private Master master; 
  public Detail() { }
  public int getId() {
    return id;
  }
  public void setId(int id) {
    this.id = id;
  }
  public Master getMaster() {
    return master;
  }
  public void setMaster(Master master) {
    this.master = master;
  }
}

SELECT e FROM Master e LEFT JOIN FETCH e.detail

Hibernate:
    select
        master0_.ID as ID1_0_,
        detail1_.ID as ID0_1_,
        detail1_.master_id as master2_0_1_
    from
        master master0_
    left outer join
        detail detail1_
            on master0_.ID=detail1_.master_id

SELECT e FROM Detail e LEFT JOIN FETCH e.master

Hibernate:
    select
        detail0_.ID as ID0_0_,
        master1_.ID as ID1_1_,
        detail0_.master_id as master2_0_0_
    from
        detail detail0_
    left outer join
        master master1_
            on detail0_.master_id=master1_.ID
Hibernate:
    select
        detail0_.ID as ID0_0_,
        detail0_.master_id as master2_0_0_
    from
        detail detail0_
    where
        detail0_.master_id=?
Hibernate:
    select
        detail0_.ID as ID0_0_,
        detail0_.master_id as master2_0_0_
    from
        detail detail0_
    where
        detail0_.master_id=?
...

@Entity @Table(name = "master")
public class Master implements java.io.Serializable {
-----
----

public void setDetail(Detail detail) {
    this.detail = detail;
    details.setMaster(this); //This line need to be added
  }

}