这篇 单向的多对多关联映射

1.如何在权限管理中，角色和权限之间的关系就是多对多的关系，表结构为：

2.类结构

Permission.java

public class Permission implements Serializable{    private int id;    private String name;    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;    }    }

Role.java

public class Role implements Serializable{    private int id;    private String name;    private Set
     
       permissions=new HashSet
      
       ();//这个地方特别容易忘记，，，    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
       
         getPermissions() {        return permissions;    }    public void setPermissions(Set
        
          permissions) {        this.permissions = permissions;    }}
        
       
      
     

3.映射文件

Permission.hbm.xml

Role.hbm.xml

4.测试

public class HibernateTest {    /**     * 生成数据库表的工具方法     * */    @Test    public void testCreateDB(){        Configuration cfg = new Configuration().configure();        SchemaExport se = new SchemaExport(cfg);        //第一个参数  是否打印sql脚本        //第二个参数 是否将脚本导出到数据库中执行        se.create(true, true);    }    /**     * 初始化表数据     */    @Test    public void testInit(){        Session session = null;        Transaction tx = null;        try {            session = HibernateUtil.getSession();            tx = session.beginTransaction();            Permission p1 = new Permission("增加用户");            Permission p2 = new Permission("删除用户");            Permission p3 = new Permission("查询用户");            Permission p4 = new Permission("修改用户");                        Role r1 = new Role("管理员");            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());        }                HibernateUtil.close();    }}