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

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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;@Entitypublic class Husband {private int id;private String name;private Wife wife;@Id@GeneratedValuepublic 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;@Entitypublic class Wife {private int id;private String name;@Id@GeneratedValuepublic 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

@Testpublic 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@GeneratedValuepublic 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@GeneratedValuepublic 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;@Entitypublic class Teacher {private int id;private String name;private Set<Student> students = new HashSet<Student>();@Id@GeneratedValuepublic 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;@Entitypublic class Student {private int id;private String name;@Id@GeneratedValuepublic 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>