java之hibernate之多對多雙向關聯映射

1.好比在權限管理中，角色和權限之間的關係就是多對多的關係，表結構爲：

2.類結構

Role.java

public class Role implements Serializable{ private int id; private String name; private Set<Permission> permissions=new HashSet<Permission>(); public Role() { } public Role(String name) { super(); this.name = name; } 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; } public Set<Permission> getPermissions() { return permissions; } public void setPermissions(Set<Permission> permissions) { this.permissions = permissions; } }

Permisssion.java

public class Permission implements Serializable{ private int id; private String name; private Set<Role> roles; public Permission() { // TODO Auto-generated constructor stub
 } public Permission(String name) { super(); this.name = name; } 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; } public Set<Role> getRoles() { return roles; } public void setRoles(Set<Role> roles) { this.roles = roles; } }

3.映射文件信息

Role.hbm.xml

<hibernate-mapping package="cn.sxt.pojo">
    <class name="Role" table="t_role">
        <id name="id">
            <generator class="native">
            </generator>
        </id>
        <property name="name"/>
        <set name="permissions" table="t_role_permission">
            <!-- 當前類在鏈接表中的外鍵 -->
            <key column="rid"></key>
            <many-to-many column="pid" class="Permission"></many-to-many>
        </set>
    </class>
</hibernate-mapping>

Permission.hbm.xml

<hibernate-mapping package="cn.sxt.pojo">
    <class name="Permission" table="t_permission">
        <id name="id">
            <generator class="native">
            </generator>
        </id>
        <property name="name"/>
        <set name="roles" table="t_role_permission" inverse="true">
            <!-- 當前類在鏈接表中的外鍵 -->
            <key column="pid"></key>
            <many-to-many column="rid" class="Role"></many-to-many>
        </set>
    </class>
</hibernate-mapping>

4.測試

public class HibernateTest { /** * 生成數據庫表的工具方法 * */ @Test public void testCreateDB(){ Configuration cfg = new Configuration().configure(); SchemaExport se = new SchemaExport(cfg); //第一個參數 是否打印sql腳本 //第二個參數 是否將腳本導出到數據庫中執行
        se.create(true, true); } /** * 初始化表數據 */ @Test public void testInit(){ Session session = null; Transaction tx = null; try { session = HibernateUtil.getSession(); tx = session.beginTransaction(); Permission p1 = new Permission("增長用戶"); Permission p2 = new Permission("刪除用戶"); Permission p3 = new Permission("查詢用戶"); Permission p4 = new Permission("修改用戶"); Role r1 = new Role("管理員"); r1.getPermissions().add(p1); r1.getPermissions().add(p2); r1.getPermissions().add(p3); r1.getPermissions().add(p4); Role r2 = new Role("vip");  r2.getPermissions().add(p3); r2.getPermissions().add(p4); session.save(p1); session.save(p2); session.save(p3); session.save(p4); session.save(r1); session.save(r2); tx.commit(); } catch (Exception e) { if(tx!=null) tx.rollback(); }finally { HibernateUtil.close(); } } /**
     */ @Test public void testGetData(){ Session session = HibernateUtil.getSession(); Role role = (Role)session.get(Role.class, 1); System.out.println(role.getId()+"---"+role.getName()); System.out.println("-------------"); for(Permission p:role.getPermissions()){ System.out.println(p.getId()+"---"+p.getName()); } System.out.println("=========================="); Permission p = (Permission)session.get(Permission.class, 3); System.out.println(p.getId()+"----"+p.getName()); for(Role r:p.getRoles()){ System.out.println(r.getId()+"---"+r.getName()); } HibernateUtil.close(); } }