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HiberNate学习-2映射关系

 
阅读更多

 1.Hibernate的一对一主键关联映射

 

默认cascade属性为true;

 

核心代码：

1.主键生成策略：

Xml代码 复制代码 收藏代码
  1. <!-- Person的主键来源于idCard, 也就是共享idCard主键 -->
  2. <generatorclass="foreign">
  3. <paramname="property">idCard</param>
  4. </generator>
<!-- Person的主键来源于idCard, 也就是共享idCard主键 -->
<generator class="foreign">
	<param name="property">idCard</param>
</generator>

2.one-to-one配置

Java代码 复制代码 收藏代码
  1. <!-- one-to-one标签的含义，指示hibernate怎样加载它的关联对象，默认根据主键加载
  2. constrained="true",表明当前主键上存在一个约束，person的主键作为外键参照了idcard
  3. -->
  4. <one-to-one name="idCard" constrained="true" /> 
<!-- one-to-one标签的含义，指示hibernate怎样加载它的关联对象，默认根据主键加载
	constrained="true",表明当前主键上存在一个约束，person的主键作为外键参照了idcard
 -->
<one-to-one name="idCard" constrained="true" />

 

 

一：实体类：

Person.java代码 复制代码 收藏代码
  1. package com.tao.hibernate.one2one;
  3. public class Person {
  4. private Integer id;
  5. private String name;
  6. private IdCard idCard;
  8. public Person() {
  9. super();
  10. }
  12. public Integer getId() {
  13. return id;
  14. }
  16. public void setId(Integer id) {
  17. this.id = id;
  18. }
  20. public String getName() {
  21. return name;
  22. }
  24. public void setName(String name) {
  25. this.name = name;
  26. }
  28. public IdCard getIdCard() {
  29. return idCard;
  30. }
  32. public void setIdCard(IdCard idCard) {
  33. this.idCard = idCard;
  34. }
  36. } 
package com.tao.hibernate.one2one;

public class Person {
	private Integer id;
	private String name;
	private IdCard idCard;

	public Person() {
		super();
	}

	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;
	}

}

 

Idcard.java代码 复制代码 收藏代码
  1. package com.tao.hibernate.one2one;
  3. public class IdCard {
  4. private Integer id;
  5. private String cardNo;
  6. private Person person;
  8. public IdCard() {
  9. super();
  10. }
  12. public Integer getId() {
  13. return id;
  14. }
  16. public void setId(Integer id) {
  17. this.id = id;
  18. }
  20. public String getCardNo() {
  21. return cardNo;
  22. }
  24. public void setCardNo(String cardNo) {
  25. this.cardNo = cardNo;
  26. }
  28. public Person getPerson() {
  29. return person;
  30. }
  32. public void setPerson(Person person) {
  33. this.person = person;
  34. }
  36. } 
package com.tao.hibernate.one2one;

public class IdCard {
	private Integer id;
	private String cardNo;
	private Person person;

	public IdCard() {
		super();
	}

	public Integer getId() {
		return id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public String getCardNo() {
		return cardNo;
	}

	public void setCardNo(String cardNo) {
		this.cardNo = cardNo;
	}

	public Person getPerson() {
		return person;
	}

	public void setPerson(Person person) {
		this.person = person;
	}

}

二：映射文件：

Person.hbm.xml代码 复制代码 收藏代码
  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  3. "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
  5. <hibernate-mapping package="com.tao.hibernate.one2one">
  6. <class name="Person" table="t_Person">
  7. <id name="id" column="id" type="integer">
  8. <!-- Person的主键来源于idCard, 也就是共享idCard主键 -->
  9. <generator class="foreign">
  10. <param name="property">idCard</param>
  11. </generator>
  12. </id>
  13. <property name="name" column="name" />
  14. <!-- one-to-one标签的含义，指示hibernate怎样加载它的关联对象，默认根据主键加载
  15. constrained="true",表明当前主键上存在一个约束，person的主键作为外键参照了idcard
  16. -->
  17. <one-to-one name="idCard" constrained="true" />
  18. </class>
  19. </hibernate-mapping> 
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.tao.hibernate.one2one">
	<class name="Person" table="t_Person">
		<id name="id" column="id" type="integer">
			<!-- Person的主键来源于idCard, 也就是共享idCard主键 -->
			<generator class="foreign">
				<param name="property">idCard</param>
			</generator>
		</id>
		<property name="name" column="name" />
		<!-- one-to-one标签的含义，指示hibernate怎样加载它的关联对象，默认根据主键加载
			constrained="true",表明当前主键上存在一个约束，person的主键作为外键参照了idcard
		 -->
		<one-to-one name="idCard" constrained="true" />
	</class>
</hibernate-mapping>

 

Idcard.hbm.xml代码 复制代码 收藏代码
  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  3. "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
  5. <hibernate-mapping package="com.tao.hibernate.one2one">
  6. <class name="IdCard" table="t_IdCard">
  7. <id name="id" column="id" type="integer">
  8. <generator class="native" />
  9. </id>
  10. <property name="cardNo" column="cardNo" />
  11. <one-to-one name="person" fetch="select"/>
  12. </class>
  13. </hibernate-mapping> 
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.tao.hibernate.one2one">
	<class name="IdCard" table="t_IdCard">
		<id name="id" column="id" type="integer">
			<generator class="native" />
		</id>
		<property name="cardNo" column="cardNo" />
		<one-to-one name="person" fetch="select"/>
	</class>
</hibernate-mapping>

三：测试类

Java代码 复制代码 收藏代码
  1. package com.tao.hibernate.one2one;
  3. import org.hibernate.Session;
  4. import org.hibernate.Transaction;
  5. import org.junit.Test;
  7. import com.tao.hibernate.HibernateUtils;
  9. publicclass TestMain {
  11. @Test
  12. publicvoid testSave() {
  13. Session session = HibernateUtils.getFactory().openSession();
  15. IdCard idCard = new IdCard();
  16. idCard.setCardNo("100");
  18. Person person = new Person();
  19. person.setName("Tao");
  20. person.setIdCard(idCard);
  22. Transaction ts = session.beginTransaction();
  23. ts.begin();
  24. session.save(person);
  25. ts.commit();
  26. }
  28. @Test
  29. publicvoid testLoad() {
  30. Session session = HibernateUtils.getFactory().openSession();
  31. Person person = (Person) session.load(Person.class, 2);
  32. System.out.println(person.getName());
  33. System.out.println(person.getIdCard().getCardNo());
  34. }
  36. @Test
  37. publicvoid testLoad2() {
  38. Session session = HibernateUtils.getFactory().openSession();
  39. IdCard idCard = (IdCard) session.load(IdCard.class, 2);
  40. System.out.println(idCard.getCardNo());
  41. System.out.println(idCard.getPerson().getName());
  42. }
  44. }

2 Hibernate的一对一唯一外键关联映射

一对一唯一外键关联映射实际上是多对一关联映射的特例。

 

可以采用many-to-one标签，指定多的一端的unique=true,这样就限制了多的一端的多重性唯一。

通过这种手段映射一对一唯一外键关联。

<many-to-one name="idCard" unique="true"/>

 

一对一唯一外键关联双向，需要在另一端（idCard），添加<one-to-one>标签，指示hibernate如何加载其关联对象，默认根据主键加载，外键关联映射中，因为两个实体采用的是person外键维护的关系，所以不能指定主键加载person，而要根据person的外键加载，所以采用如下映射方式：

<one-to-one name="person" property-ref="idCard">

 

一：实体类：

Idcard2.java代码 复制代码 收藏代码
  1. package com.tao.hibernate.one2one2;
  3. public class IdCard2 {
  4. private Integer id;
  5. private String cardNo;
  6. private Person2 person;
  8. public IdCard2() {
  9. super();
  10. }
  12. public Integer getId() {
  13. return id;
  14. }
  16. public void setId(Integer id) {
  17. this.id = id;
  18. }
  20. public String getCardNo() {
  21. return cardNo;
  22. }
  24. public void setCardNo(String cardNo) {
  25. this.cardNo = cardNo;
  26. }
  28. public Person2 getPerson() {
  29. return person;
  30. }
  32. public void setPerson(Person2 person) {
  33. this.person = person;
  34. }
  36. } 
package com.tao.hibernate.one2one2;

public class IdCard2 {
	private Integer id;
	private String cardNo;
	private Person2 person;

	public IdCard2() {
		super();
	}

	public Integer getId() {
		return id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public String getCardNo() {
		return cardNo;
	}

	public void setCardNo(String cardNo) {
		this.cardNo = cardNo;
	}

	public Person2 getPerson() {
		return person;
	}

	public void setPerson(Person2 person) {
		this.person = person;
	}

}

 

Person2.java代码 复制代码 收藏代码
  1. package com.tao.hibernate.one2one2;
  4. public class Person2 {
  5. private Integer id;
  6. private String name;
  7. private IdCard2 idCard;
  9. public Person2() {
  10. super();
  11. }
  13. public Integer getId() {
  14. return id;
  15. }
  17. public void setId(Integer id) {
  18. this.id = id;
  19. }
  21. public String getName() {
  22. return name;
  23. }
  25. public void setName(String name) {
  26. this.name = name;
  27. }
  29. public IdCard2 getIdCard() {
  30. return idCard;
  31. }
  33. public void setIdCard(IdCard2 idCard2) {
  34. this.idCard = idCard2;
  35. }
  37. } 
package com.tao.hibernate.one2one2;


public class Person2 {
	private Integer id;
	private String name;
	private IdCard2 idCard;

	public Person2() {
		super();
	}

	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 IdCard2 getIdCard() {
		return idCard;
	}

	public void setIdCard(IdCard2 idCard2) {
		this.idCard = idCard2;
	}

}

 

二：映射文件：

Idcard2.hbm.xml代码 复制代码 收藏代码
  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  3. "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
  5. <hibernate-mapping package="com.tao.hibernate.one2one2">
  6. <class name="IdCard2" table="t_IdCard2">
  7. <id name="id" column="id" type="integer">
  8. <generator class="native" />
  9. </id>
  10. <property name="cardNo" column="cardNo" />
  11. <one-to-one name="person" property-ref="idCard" />
  12. </class>
  13. </hibernate-mapping> 
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.tao.hibernate.one2one2">
	<class name="IdCard2" table="t_IdCard2">
		<id name="id" column="id" type="integer">
			<generator class="native" />
		</id>
		<property name="cardNo" column="cardNo" />
		<one-to-one name="person" property-ref="idCard" />
	</class>
</hibernate-mapping>

 

Person2.hbm.xml代码 复制代码 收藏代码
  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  3. "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
  5. <hibernate-mapping package="com.tao.hibernate.one2one2">
  6. <class name="Person2" table="t_Person2">
  7. <id name="id" column="id" type="integer">
  8. <generator class="native">
  9. </generator>
  10. </id>
  11. <property name="name" column="name" />
  12. <many-to-one name="idCard" unique="true"/>
  13. </class>
  14. </hibernate-mapping> 
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.tao.hibernate.one2one2">
	<class name="Person2" table="t_Person2">
		<id name="id" column="id" type="integer">
			<generator class="native">
			</generator>
		</id>
		<property name="name" column="name" />
		<many-to-one name="idCard" unique="true"/>
	</class>
</hibernate-mapping>

 

三：测试类：

Java代码 复制代码 收藏代码
  1. package com.tao.hibernate.one2one2;
  3. import org.hibernate.Session;
  4. import org.hibernate.Transaction;
  5. import org.junit.Test;
  7. import com.tao.hibernate.HibernateUtils;
  9. publicclass TestMain {
  11. @Test
  12. publicvoid testSave() {
  13. Session session = HibernateUtils.getFactory().openSession();
  15. IdCard2 idCard = new IdCard2();
  16. idCard.setCardNo("100");
  18. Person2 person = new Person2();
  19. person.setName("Tao");
  20. person.setIdCard(idCard);
  22. Transaction ts = session.beginTransaction();
  23. ts.begin();
  24. session.save(idCard);
  25. session.save(person);
  26. ts.commit();
  27. }
  29. @Test
  30. publicvoid testLoad() {
  31. Session session = HibernateUtils.getFactory().openSession();
  32. Person2 person = (Person2) session.load(Person2.class, 1);
  33. //System.out.println(person.getName());
  34. System.out.println(person.getIdCard().getCardNo());
  35. }
  37. @Test
  38. publicvoid testLoad2() {
  39. Session session = HibernateUtils.getFactory().openSession();
  40. IdCard2 idCard = (IdCard2) session.load(IdCard2.class, 1);
  41. System.out.println(idCard.getCardNo());
  42. System.out.println(idCard.getPerson().getName());
  43. }
  45. }  

 

3  hibernate多对一关联映射

关联映射的本质：
* 将关联关系映射到数据库，所谓的关联关系是对象模型在内存中的一个或多个引用

<many-to-one>会在多的一端加入一个外键，指向一的一端，这个外键是由<many-to-one>
中的column属性定义的，如果忽略了这个属性那么默认的外键与实体的属性一致

<many-to-one>标签的定义示例：
* <many-to-one name="group" column="groupid"/>

理解级联的含义？
* 是对象的连锁操作

 

一：实体类

Group.java代码 复制代码 收藏代码
  1. package com.tao.hibernate.many2one;
  3. public class Group {
  4. private Integer id;
  5. private String name;
  7. public Group() {
  8. super();
  9. }
  11. public Integer getId() {
  12. return id;
  13. }
  15. public void setId(Integer id) {
  16. this.id = id;
  17. }
  19. public String getName() {
  20. return name;
  21. }
  23. public void setName(String name) {
  24. this.name = name;
  25. }
  27. } 
package com.tao.hibernate.many2one;

public class Group {
	private Integer id;
	private String name;

	public Group() {
		super();
	}

	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;
	}

}

 

User.java代码 复制代码 收藏代码
  1. package com.tao.hibernate.many2one;
  3. public class User {
  4. private Integer id;
  5. private String name;
  6. private Group group;
  8. public User() {
  9. super();
  10. }
  12. public Integer getId() {
  13. return id;
  14. }
  16. public void setId(Integer id) {
  17. this.id = id;
  18. }
  20. public String getName() {
  21. return name;
  22. }
  24. public void setName(String name) {
  25. this.name = name;
  26. }
  28. public Group getGroup() {
  29. return group;
  30. }
  32. public void setGroup(Group group) {
  33. this.group = group;
  34. }
  36. } 
package com.tao.hibernate.many2one;

public class User {
	private Integer id;
	private String name;
	private Group group;

	public User() {
		super();
	}

	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 Group getGroup() {
		return group;
	}

	public void setGroup(Group group) {
		this.group = group;
	}

}

 

二：映射文件

Group.hbm.xml代码 复制代码 收藏代码
  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  3. "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
  5. <hibernate-mapping package="com.tao.hibernate.many2one">
  6. <class name="Group" table="t_group">
  7. <id name="id" column="id" type="integer">
  8. <generator class="native">
  9. </generator>
  10. </id>
  11. <property name="name" column="name" />
  12. </class>
  13. </hibernate-mapping> 
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.tao.hibernate.many2one">
	<class name="Group" table="t_group">
		<id name="id" column="id" type="integer">
			<generator class="native">
			</generator>
		</id>
		<property name="name" column="name" />
	</class>
</hibernate-mapping>

 

User.hbm.xml代码 复制代码 收藏代码
  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  3. "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
  5. <hibernate-mapping package="com.tao.hibernate.many2one">
  6. <class name="User" table="t_user">
  7. <id name="id" column="id" type="integer">
  8. <generator class="native">
  9. </generator>
  10. </id>
  11. <property name="name" column="name" />
  12. <many-to-one name="group" column="groupId"/>
  13. </class>
  14. </hibernate-mapping> 
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.tao.hibernate.many2one">
	<class name="User" table="t_user">
		<id name="id" column="id" type="integer">
			<generator class="native">
			</generator>
		</id>
		<property name="name" column="name" />
		<many-to-one name="group" column="groupId"/>
	</class>
</hibernate-mapping>

 

三：测试类：

Testmain .java代码 复制代码 收藏代码
  1. package com.tao.hibernate.many2one;
  3. import org.hibernate.Session;
  4. import org.hibernate.Transaction;
  5. import org.junit.Test;
  7. import com.tao.hibernate.HibernateUtils;
  9. public class TestMain {
  10. Session session = HibernateUtils.getFactory().openSession();
  12. @Test
  13. public void testSave() {
  14. Group group = new Group();
  15. group.setName("second group");
  17. User user = new User();
  18. user.setName("Tao2");
  19. user.setGroup(group);
  21. Transaction ts = session.beginTransaction();
  22. ts.begin();
  23. session.save(group);
  24. session.save(user);
  25. ts.commit();
  26. }
  28. @Test
  29. public void testLoad() {
  30. Session session = HibernateUtils.getFactory().openSession();
  31. User user = (User) session.load(User.class, 1);
  32. System.out.println(user.getName());
  33. System.out.println(user.getGroup().getName());
  34. }
  36. }
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