1.在一对多的关联映射中，表结构如下

2.实体类结构

User.java

public class User implements Serializable{    private int id;    private String name;    private int age;    private int roleId;    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 int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    public int getRoleId() {        return roleId;    }    public void setRoleId(int roleId) {        this.roleId = roleId;    }    @Override    public String toString() {        return "User [id=" + id + ", name=" + name + ", age=" + age + ", roleId=" + roleId +  "]";    }}

Role.java

public class Role {    private int id;    private String name;    private List
     
       users;    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 List
      
        getUsers() {        return users;    }    public void setUsers(List
       
         users) {        this.users = users;    }    @Override    public String toString() {        return "Role [id=" + id + ", name=" + name + "]";    }}
       
      
     

3.映射文件

         
              select u.id as uid,u.name as uname,u.age as uage,        roleId,r.name as rname from t_user u,t_role r         where u.roleId=r.id and r.id=#{id}        
              
               
               
                   
                    
                    
                    
                
           
      
     

4.测试

　　@Test    public void testFindById() throws IOException{        SqlSession session = MybatisUtil.getSqlSession();        Role role = (Role)session.selectOne("cn.sxt.vo.RoleMapper.findById",2);        System.out.println(role.getId()+"-----"+role.getName());        for(User u:role.getUsers()){            System.out.println(u);        }        session.close();    }

5.使用2个映射语句实现映射

RoleMapper.xml

        select * from t_role where id=#{id}        
             
              
              
              
          
     

UserMapper.xml

         
              select * from t_user where roleId=#{roleId}