Hibernate关联查询

@Test
	public void Test1() {
		Session session = null;
		Transaction transaction = null;
		try {
			// 创建session
			session = HibernateUntil.getSession();
			// 开始事务
			transaction = session.beginTransaction();
			//查询id=1的husband数据，这里将会使用左外连接查询数据，直接联表查询
			Husband husband=session.get(Husband.class, 1);

			//获取Husband中的Wife对象属性
			Wife wife=husband.getWife();

			//输出wife的属性age的值，由于前面已经查询过了，因此这里不再发出sql语句
			System.out.println(wife.getAge());

			// 提交事务
			transaction.commit();
		} catch (Exception exception) {
			transaction.rollback(); // 事务回滚
		} finally {
			if (session!=null) {
				session.close();
			}
		}

@Entity   //指定实体类
@Table(name="husband")   //指定对应数据库的表名为husband
public class Husband {
	private int id;
	private String name;
	private int age;
	private Wife wife;   //Wife对象
	@Id
	@GeneratedValue   //主键生成策略，自增长
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	@OneToOne(fetch=FetchType.LAZY)   //设置wife的主键为Husband的外键，默认的对应表中的字段为wife_id
	@JoinColumn(name="wifeid") // 默认外键的名字为wife_id.我们使用这个注解改变外键的名字为wifeid
	public Wife getWife() {
		return this.wife;
	}
	public void setWife(Wife wife) {
		this.wife = wife;
	}
	@Column(length=20)   //设置长度为20
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	@Override
	public String toString() {
		return "Husband [id=" + id + ", name=" + name + ", age=" + age
				+ ", Wife=" + this.wife + "]";
	}
}

@Test
	public void Test1() {
		Session session = null;
		Transaction transaction = null;
		try {
			// 创建session
			session = HibernateUntil.getSession();
			// 开始事务
			transaction = session.beginTransaction();
			//查询id=1的husband数据，这里使用懒加载，只会查找husband的表，并不会联表查询
			Husband husband=session.get(Husband.class, 1);

			//获取Husband中的Wife对象属性，此处依然没有查询wife表
			Wife wife=husband.getWife();

			//输出wife的属性age的值，此处发出sql语句查询wife表，验证了只有当用到的wife属性的时候才会发出查询语句
			System.out.println(wife.getAge());

			// 提交事务
			transaction.commit();
		} catch (Exception exception) {
			transaction.rollback(); // 事务回滚
		} finally {
			if (session!=null) {
				session.close();
			}
		}
	}