第九章 关系映射 多对多关联映射
2013-06-08 10:00
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表设计:
有一张中间表,中间表中有两张关联表的外键
如:student与teacher
Student:
package cn.framelife.mvc.entity;
import java.util.Set;
public class Student {
private Integer id;
private String name;
private Set<Teacher> teachers;
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 Set<Teacher> getTeachers() {
return teachers;
}
public void setTeachers(Set<Teacher> teachers) {
this.teachers = teachers;
}
}
Teacher:
package cn.framelife.mvc.entity;
import java.util.Set;
public class Teacher {
private Integer id;
private String name;
private Set<Student> students;
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 Set<Student> getStudents() {
return students;
}
public void setStudents(Set<Student> students) {
this.students = students;
}
}
Student.hbm.xml:
<hibernate-mapping>
<class name="cn.framelife.hibernate.entity.Student" table="student">
<id name="id" type="java.lang.Integer">
<column name="id" />
<generator class="native" />
</id>
<property name="name" type="java.lang.String">
<column name="s_name" length="45" not-null="true" />
</property>
<set name="teachers" table="s_t" cascade="all">
<key column="student_id"/>
<many-to-many column="teacher_id" class="cn.framelife.hibernate.entity.Teacher"></many-to-many>
</set>
</class>
</hibernate-mapping>
Teacher.hbm.xml:
<hibernate-mapping>
<class name="cn.framelife.hibernate.entity.Teacher" table="teacher" catalog="hibernate">
<id name="id" type="java.lang.Integer">
<column name="id" />
<generator class="native" />
</id>
<property name="name" type="java.lang.String">
<column name="t_name" length="45" not-null="true" />
</property>
<set name="students" table="s_t" >
<key column="teacher_id"/>
<many-to-many column="student_id" class="cn.framelife.hibernate.entity.Student"></many-to-many>
</set>
</class>
</hibernate-mapping>
增加:
Student s1 = new Student();
s1.setName("s10");
Student s2 = new Student();
s2.setName("s11");
Set<Teacher> set = new HashSet<Teacher>();
Teacher t1 = new Teacher();
t1.setName("t10");
Teacher t2 = new Teacher();
t2.setName("t11");
set.add(t1);
set.add(t2);
//设置学生与老师的的关系
s1.setTeachers(set);
s2.setTeachers(set);
//增加两个学生,同时会把老师也加到数据库中
session.save(s1);
session.save(s2);
有一张中间表,中间表中有两张关联表的外键
如:student与teacher
Student:
package cn.framelife.mvc.entity;
import java.util.Set;
public class Student {
private Integer id;
private String name;
private Set<Teacher> teachers;
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 Set<Teacher> getTeachers() {
return teachers;
}
public void setTeachers(Set<Teacher> teachers) {
this.teachers = teachers;
}
}
Teacher:
package cn.framelife.mvc.entity;
import java.util.Set;
public class Teacher {
private Integer id;
private String name;
private Set<Student> students;
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 Set<Student> getStudents() {
return students;
}
public void setStudents(Set<Student> students) {
this.students = students;
}
}
Student.hbm.xml:
<hibernate-mapping>
<class name="cn.framelife.hibernate.entity.Student" table="student">
<id name="id" type="java.lang.Integer">
<column name="id" />
<generator class="native" />
</id>
<property name="name" type="java.lang.String">
<column name="s_name" length="45" not-null="true" />
</property>
<set name="teachers" table="s_t" cascade="all">
<key column="student_id"/>
<many-to-many column="teacher_id" class="cn.framelife.hibernate.entity.Teacher"></many-to-many>
</set>
</class>
</hibernate-mapping>
Teacher.hbm.xml:
<hibernate-mapping>
<class name="cn.framelife.hibernate.entity.Teacher" table="teacher" catalog="hibernate">
<id name="id" type="java.lang.Integer">
<column name="id" />
<generator class="native" />
</id>
<property name="name" type="java.lang.String">
<column name="t_name" length="45" not-null="true" />
</property>
<set name="students" table="s_t" >
<key column="teacher_id"/>
<many-to-many column="student_id" class="cn.framelife.hibernate.entity.Student"></many-to-many>
</set>
</class>
</hibernate-mapping>
增加:
Student s1 = new Student();
s1.setName("s10");
Student s2 = new Student();
s2.setName("s11");
Set<Teacher> set = new HashSet<Teacher>();
Teacher t1 = new Teacher();
t1.setName("t10");
Teacher t2 = new Teacher();
t2.setName("t11");
set.add(t1);
set.add(t2);
//设置学生与老师的的关系
s1.setTeachers(set);
s2.setTeachers(set);
//增加两个学生,同时会把老师也加到数据库中
session.save(s1);
session.save(s2);
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