学习笔记-----------表之间的关联(one-to-one many-to-one many-to-many)

技术2022-05-20 39

一.Hibernate3.3.2_一对一单向外键关联_annotation

1.Husband.java private Wife wife让他们有关联，对象的引用。

package com.bjsxt.hibernate; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.OneToOne; @Entity public class Husband { private int id; private String name; private Wife wife; @Id @GeneratedValue public int getId() { return id; } public String getName() { return name; } @OneToOne @JoinColumn(name="wifeId") public Wife getWife() { return wife; } public void setId(int id) { this.id = id; } public void setName(String name) { this.name = name; } public void setWife(Wife wife) { this.wife = wife; } }

2.Wife.java

package com.bjsxt.hibernate; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; @Entity public class Wife { private int id; private String name; @Id @GeneratedValue public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } }

3.src目录下hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://localhost/hibernate</property> <property name="connection.username">root</property> <property name="connection.password">bjsxt</property> <property name="dialect">org.hibernate.dialect.MySQLDialect</property>   <property name="connection.pool_size">1</property>  <property name="current_session_context_class">thread</property>  <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>  <property name="show_sql">true</property> <property name="format_sql">true</property>   <mapping class="com.bjsxt.hibernate.Husband"/> <mapping class="com.bjsxt.hibernate.Wife"/> </session-factory> </hibernate-configuration>

4.测试junit

@Test public void testSchemaExport() { new SchemaExport(new AnnotationConfiguration().configure()).create(false, true); }

二.Hibernate3.3.2_一对一单向外键关联_xml

Husband..hbm.xml 这个配置不能直接使用修要自行修改。<many-to-one name="wife" column="wifeId" unique="true"></many-to-one>是主要的参考，不需要注解时用这句话。

<?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> <class name="com.bjsxt.hibernate.StuIdCard"> <id name="id"> <generator class="native"></generator> </id> <property name="num"/> <many-to-one name="wife" column="wifeId" unique="true"></many-to-one> </class> </hibernate-mapping>

三.Hibernate3.3.2_一对一双向外键关联annotation

查文档

四.一对多one-to-many，@JoinColumn(name="groupId")这就很重要，没有会当成many-to-many生成第三张表。

1.Group.java

package com.bjsxt.hibernate; import java.util.HashSet; import java.util.Set; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.OneToMany; import javax.persistence.Table; @Entity @Table(name="t_group") public class Group { private int id; private String name; private Set<User> users = new HashSet<User>(); @Id @GeneratedValue public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } @OneToMany @JoinColumn(name="groupId") public Set<User> getUsers() { return users; } public void setUsers(Set<User> users) { this.users = users; } }

2.User.java

package com.bjsxt.hibernate; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.ManyToOne; import javax.persistence.Table; @Entity @Table(name="t_user") public class User { private int id; private String name; @Id @GeneratedValue public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } }

3.使用配置文件

Group.hbm.xml

<?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> <class name="com.bjsxt.hibernate.Group" table="t_group"> <id name="id"> <generator class="native"></generator> </id> <property name="name"></property> <set name="users"> <key column="groupId"></key> <one-to-many class="com.bjsxt.hibernate.User"/> </set> </class> </hibernate-mapping>

4.User.hbm.xml

<?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> <class name="com.bjsxt.hibernate.User" table="t_user"> <id name="id"> <generator class="native"></generator> </id> <property name="name"></property> </class> </hibernate-mapping>

5.hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://localhost/hibernate</property> <property name="connection.username">root</property> <property name="connection.password">bjsxt</property> <property name="dialect">org.hibernate.dialect.MySQLDialect</property>   <property name="connection.pool_size">1</property>  <property name="current_session_context_class">thread</property>  <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>  <property name="show_sql">true</property> <property name="format_sql">true</property>   <mapping resource="com/bjsxt/hibernate/Group.hbm.xml"/> <mapping resource="com/bjsxt/hibernate/User.hbm.xml"/> </session-factory> </hibernate-configuration>

6,注意凡是双向都要使用mappedby否则会生成多余列field冗余，要在多的那方写（但这是被动的，须在小的写语句）

多用annotation较方便快捷简单容易。

五.Hibernate3.3.2__多对多单向关联

1.Teacher.java

package com.bjsxt.hibernate; import java.util.HashSet; import java.util.Set; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.JoinTable; import javax.persistence.ManyToMany; import javax.persistence.OneToMany; import javax.persistence.Table; @Entity public class Teacher { private int id; private String name; private Set<Student> students = new HashSet<Student>(); @Id @GeneratedValue public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } @ManyToMany @JoinTable(name="t_s", joinColumns={@JoinColumn(name="teacher_id")}, inverseJoinColumns={@JoinColumn(name="student_id")} ) public Set<Student> getStudents() { return students; } public void setStudents(Set<Student> students) { this.students = students; } }

2.Student.java

package com.bjsxt.hibernate; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.ManyToOne; import javax.persistence.Table; @Entity public class Student { private int id; private String name; @Id @GeneratedValue public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } }

3.Student.hbm.xml

<?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> <class name="com.bjsxt.hibernate.Student"> <id name="id"> <generator class="native"></generator> </id> <property name="name"></property> </class> </hibernate-mapping>

4.Teacher.hbm.xml

<?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> <class name="com.bjsxt.hibernate.Teacher"> <id name="id"> <generator class="native"></generator> </id> <property name="name"></property> <set name="students" table="t_s"> <key column="teacher_id"></key> <many-to-many class="com.bjsxt.hibernate.Student" column="student_id"/> </set> </class> </hibernate-mapping>

专利

最新回复(0)