Hibernate映射关系配置（四）

多对多单向：

Bean：

public class Student implements Serializable {

    private int id ;

    private String name ;

    private Set<Teacher> teachers ;
        ....
}
public class Teacher implements Serializable{

    private int id ;

    private String  name ;
    ....
}

xml:

Student.hbm.xml:
<class name = "Student">
        <!-- id是来配置主键
             name是类中的哪个属性和主键映射
             generator:表示主键的生成策略
        -->
        <id name = "id">
            <generator class="native" />
        </id>
        <!-- property是用来把类中的属性和表的字段做一一对应 -->
        <property name="name" />

        <set name="teachers" table="t_s">
            <!-- key 会在指定的表中新添加列,外键-->
            <key column="sid" />
            <many-to-many class="Teacher" column="tid" />
        </set>

    </class>
Teacher.hbm.xml:
<class name = "Teacher">
        <!-- id是来配置主键
             name是类中的哪个属性和主键映射
             generator:表示主键的生成策略
        -->
        <id name = "id">
            <generator class="native" />
        </id>
        <property name="name" />
    </class>

annotation：

@Entity
public class Student implements Serializable {
        @Id @GeneratedValue
    public int getId() {
        return id;
    }
        /**
     * joinColumns 是指定第三张表中的哪个字段引用当前类对应的表的主键
     * inverseJoinColumns 是指定第三张表中的哪个字段引用关联的另一张表的主键
     * @return
     */
    @ManyToMany
    @JoinTable(name="ts",joinColumns={
            @JoinColumn(name="sid")
    },inverseJoinColumns={
            @JoinColumn(name="tid")
    })
    public Set<Teacher> getTeachers() {
        return teachers;
    }
}

@Entity
public class Teacher implements Serializable{
        @Id @GeneratedValue
    public int getId() {
        return id;
    }
}

多对多双向：

Bean:

public class Student implements Serializable {

    private int id ;

    private String name ;

    private Set<Teacher> teachers ;
        ....
}
public class Teacher implements Serializable{

    private int id ;

    private String  name ;

    private Set<Student> stus ;
        ....
}

Xml:

Student.hbm.xml:
        <class name = "Student">
        <!-- id是来配置主键
             name是类中的哪个属性和主键映射
             generator:表示主键的生成策略
        -->
        <id name = "id">
            <generator class="native" />
        </id>
        <!-- property是用来把类中的属性和表的字段做一一对应 -->
        <property name="name" />

        <set name="teachers" table="t_s">
            <!-- key 会在指定的表中新添加列,外键-->
            <key column="sid" />
            <many-to-many class="Teacher" column="tid" />
        </set>

    </class>

Teacher.hbm.xml:
<class name = "Teacher">
        <!-- id是来配置主键
             name是类中的哪个属性和主键映射
             generator:表示主键的生成策略
        -->
        <id name = "id">
            <generator class="native" />
        </id>
        <property name="name" />

        <set name="stus" table="t_s" cascade="all">
            <key column="tid" />
            <many-to-many column="sid" class="Student" />
        </set>
    </class>

annotation:

@Entity
public class Student implements Serializable {
        @Id @GeneratedValue
    public int getId() {
        return id;
    }
        /**
     * joinColumns 是指定第三张表中的哪个字段引用当前类对应的表的主键
     * inverseJoinColumns 是指定第三张表中的哪个字段引用关联的另一张表的主键
     * @return
     */
    @ManyToMany
    @JoinTable(name="ts",joinColumns={
            @JoinColumn(name="sid")
    },inverseJoinColumns={
            @JoinColumn(name="tid")
    })
    public Set<Teacher> getTeachers() {
        return teachers;
    }
}

@Entity
public class Teacher implements Serializable{
        @Id @GeneratedValue
    public int getId() {
        return id;
    }
        @ManyToMany(mappedBy="teachers")
    public Set<Student> getStus() {
        return stus;
    }
}