JPA使用指南 javax.persistence的注解配置_weixin_30709635的博客

@SuppressWarnings("serial")
@Entity
@Table(name="T_X")
public class X implements Serializable
{
	@Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	private int id;

	@Column(length=32)
	private String name;
	
         @Transient   //表示此数据不在数据库表里建立属性
         private String temp;

	@Temporal(TemporalType.TIMESTAMP) //这个是带时分秒的类型
	private Date date;

	@OneToOne(cascade = CascadeType.ALL, mappedBy = "x")
	private A a;
}
@SuppressWarnings("serial")
@Entity
@Table(name="T_A")
public class A implements Serializable
{
	@Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	private int id;

	@OneToMany(cascade = CascadeType.ALL, mappedBy = "a", fetch = FetchType.EAGER)
	private List<B> b = new ArrayList<B>();

	@OneToOne()
	@JoinColumn(name = "x_Id") //加这句后就会双方共同维护关系
	private X x;
}

@SuppressWarnings("serial")
@Entity
public class B implements Serializable{
         @Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	protected int id;

	@ManyToOne()
	@JoinColumn(name = "a_id")
	protected A a;
}
@SuppressWarnings("serial")
@Entity
@T