Hibernate_映射_关联关系_一对一映射2_基于外键的方式

骑猪看日落 2022-06-16 06:47 200阅读 0赞

单向关联:
    	单向一对多
    	单向多对一
    	单向多对多
    	单向一对一(只能做从有外键方到无外键方的单向关联)

<?xml version="1.0"?>
    <!DOCTYPE hibernate-mapping PUBLIC
            "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
            "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
    
    <hibernate-mapping package="cn.itcast.i_hbm_oneToOne">
    	
    	<class name="Person" table="t_person">
    		<id name="id" type="integer" column="id">
    			<generator class="native" />
    		</id>
    		<property name="name" type="string" column="name" />
    
    		
    		<one-to-one name="idCard" class="IdCard" property-ref="person" />
    	</class>
    </hibernate-mapping>

<?xml version="1.0"?>
    <!DOCTYPE hibernate-mapping PUBLIC
            "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
            "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
    
    <hibernate-mapping package="cn.itcast.i_hbm_oneToOne">
    	
    	<class name="IdCard" table="t_idcard">
    		<id name="id" type="integer" column="id">
    			<generator class="native" />
    		</id>
    		<property name="number" type="string" column="number" />
    		
    		
    		<many-to-one name="person" class="Person" column="personId" unique="true" ></many-to-one>
    	</class>
    </hibernate-mapping>

package cn.itcast.i_hbm_oneToOne;
    
    /**
     * 公民实体类
     * 
     * @author 风清杨
     * @version V1.0
     */
    public class Person {
    	private Integer id;// 主键id
    	private String name;// 姓名
    	private IdCard idCard;// 关联的身份证
    
    	public Integer getId() {
    		return id;
    	}
    
    	public void setId(Integer id) {
    		this.id = id;
    	}
    
    	public String getName() {
    		return name;
    	}
    
    	public void setName(String name) {
    		this.name = name;
    	}
    
    	public IdCard getIdCard() {
    		return idCard;
    	}
    
    	public void setIdCard(IdCard idCard) {
    		this.idCard = idCard;
    	}
    
    	@Override
    	public String toString() {
    		return "IdCard [id=" + id + ", name=" + name + "]";
    	}
    }

package cn.itcast.i_hbm_oneToOne;
    
    /**
     * 身份证 实体类
     * 
     * @author 风清杨
     * @version V1.0
     */
    public class IdCard {
    	private Integer id;// 主键
    	private String number;// 身份证编号
    	private Person person;// 关联的公民对象
    
    	public Integer getId() {
    		return id;
    	}
    
    	public void setId(Integer id) {
    		this.id = id;
    	}
    
    	public String getNumber() {
    		return number;
    	}
    
    	public void setNumber(String number) {
    		this.number = number;
    	}
    
    	public Person getPerson() {
    		return person;
    	}
    
    	public void setPerson(Person person) {
    		this.person = person;
    	}
    
    	@Override
    	public String toString() {
    		return "IdCard [id=" + id + ", number=" + number + "]";
    	}
    
    }

package cn.itcast.i_hbm_oneToOne;
    
    import org.hibernate.Session;
    import org.hibernate.SessionFactory;
    import org.hibernate.Transaction;
    import org.hibernate.cfg.Configuration;
    import org.junit.Test;
    
    /**
     * 应用程序操作类
     * 
     * @author 风清杨
     * @version V1.0
     * 
     */
    public class App {
    	private static SessionFactory sessionFactory = new Configuration()//
    			.configure()//
    			.addClass(Person.class)//
    			.addClass(IdCard.class)//
    			.buildSessionFactory();
    
    	// 保存,有关联关系
    	@Test
    	public void testSave() throws Exception {
    		Session session = sessionFactory.openSession();
    		Transaction tx = null;
    		try {
    			tx = session.beginTransaction();
    			// ------------------------------------
    
    			// 新建对象
    			Person person = new Person();
    			person.setName("张三");
    
    			IdCard idCard = new IdCard();
    			idCard.setNumber("10000001X");
    
    			// 关联起来
    			person.setIdCard(idCard);
    			idCard.setPerson(person);
    
    			// 保存
    			session.save(person);
    			session.save(idCard);
    			// ------------------------------------
    			tx.commit();
    		} catch (RuntimeException e) {
    			tx.rollback();
    			throw e;
    		} finally {
    			session.close();
    		}
    	}
    
    	// 获取,可以获取到关联的对方
    	@Test
    	public void testGet() throws Exception {
    		Session session = sessionFactory.openSession();
    		Transaction tx = null;
    		try {
    			tx = session.beginTransaction();
    			// ------------------------------------
    
    			// 获取一方数据,并显示另一方信息
    			// Person person = (Person) session.get(Person.class, 1);
    			// System.out.println(person);
    			// System.out.println(person.getIdCard());
    
    			IdCard idCard = (IdCard) session.get(IdCard.class, 1);
    			System.out.println(idCard);
    			System.out.println(idCard.getPerson());
    			// ------------------------------------
    			tx.commit();
    		} catch (RuntimeException e) {
    			tx.rollback();
    			throw e;
    		} finally {
    			session.close();
    		}
    	}
    
    	// 解除关联关系：一对一中,只能有外键可以维护关联关系
    	@Test
    	public void testRemoveRelation() throws Exception {
    		Session session = sessionFactory.openSession();
    		Transaction tx = null;
    		try {
    			tx = session.beginTransaction();
    			// ------------------------------------
    
    			// 从有外键方解除关系,可以。
    			// IdCard idCard = (IdCard) session.get(IdCard.class, 1);
    			// idCard.setPerson(null);
    
    			// 从无外键方解除关系,不可以。
    			Person person = (Person) session.get(Person.class, 1);
    			person.setIdCard(null);
    
    			// ------------------------------------
    			tx.commit();
    		} catch (RuntimeException e) {
    			tx.rollback();
    			throw e;
    		} finally {
    			session.close();
    		}
    	}
    
    	// 删除对象,对关联对象的影响
    	@Test
    	public void testDelete() throws Exception {
    		Session session = sessionFactory.openSession();
    		Transaction tx = null;
    		try {
    			tx = session.beginTransaction();
    			// ------------------------------------
    
    			// a,如果没有关联的对方：
    			// b,如果有关联的对方且可以维护关联关系(有外键方),它就会先删除关联关系,再删除自已。
    			// c,如果有关联的对方且不能维护关联关系(无外键方),所以会直接执行删除自已,就会有异常。
    			IdCard idCard = (IdCard) session.get(IdCard.class, 1);
    			session.delete(idCard);
    
    			// Person person = (Person) session.get(Person.class,1);
    			// session.delete(person);
    
    			// ------------------------------------
    			tx.commit();
    		} catch (RuntimeException e) {
    			tx.rollback();
    			throw e;
    		} finally {
    			session.close();
    		}
    	}
    }