学习mybatis的关联关系，主要注解在代码上，这里不做解释。配置文件一样的就不贴了

1.关联关系表创建（学生对应老师 多对一）

　　学生老师表

 

 2.表对应的实体类

package com.home.entity;/** * 此类是：学生 * @author hpc * @2017年1月14日下午7:06:33 */public class Student {    private Integer student_id;//学生id    private String student_name;//学生名字    private Integer student_number;//学生编号    private Teacher student_teacher;//是哪个教师的学生    public Integer getStudent_id() {        return student_id;    }    public void setStudent_id(Integer student_id) {        this.student_id = student_id;    }    public String getStudent_name() {        return student_name;    }    public void setStudent_name(String student_name) {        this.student_name = student_name;    }    public Integer getStudent_number() {        return student_number;    }    public void setStudent_number(Integer student_number) {        this.student_number = student_number;    }    public Teacher getStudent_teacher() {        return student_teacher;    }    public void setStudent_teacher(Teacher student_teacher) {        this.student_teacher = student_teacher;    }    @Override    public String toString() {        return "Student [student_id=" + student_id + ", student_name=" + student_name + ", student_number="                + student_number + ", student_teacher=" + student_teacher + "]";    }}

package com.home.entity;import java.util.HashSet;import java.util.Set;/** * 此类是：老师 * @author hpc * @2017年1月14日下午7:06:47 */public class Teacher {    private Integer teacher_id;// 老师id    private String teacher_name;// 老师名字    private Integer teacher_number;// 老师编号    private Set
     
       teacher_student = new HashSet
      
       ();// 老师教过哪些学生        public Integer getTeacher_id() {        return teacher_id;    }    public void setTeacher_id(Integer teacher_id) {        this.teacher_id = teacher_id;    }    public String getTeacher_name() {        return teacher_name;    }    public void setTeacher_name(String teacher_name) {        this.teacher_name = teacher_name;    }    public Integer getTeacher_number() {        return teacher_number;    }    public void setTeacher_number(Integer teacher_number) {        this.teacher_number = teacher_number;    }    public Set
       
         getTeacher_student() {        return teacher_student;    }    public void setTeacher_student(Set
        
          teacher_student) {        this.teacher_student = teacher_student;    }    @Override    public String toString() {        return "Teacher [teacher_id=" + teacher_id + ", teacher_name=" + teacher_name + ", teacher_number="                + teacher_number + ", teacher_student=" + teacher_student + "]";    }    }
        
       
      
     

3.核心主要是配置文件

     
     
          
          
          
              select *        from students as s join teachers as t        on t.teacher_id=s.student_teacher        where s.student_id=#{id}        
          
          
              
               
               
               
               
               
               
               
           
          
          
              
               
               
           
      
     

     
         
          
              select *        from teachers as t join students as s        on s.student_teacher=t.teacher_id        where teacher_id=#{teacher_id}        
              
               
               
               
                   
                    
                    
                
           
      
     

 4. 测试

package com.home.mybatis;import java.io.IOException;import org.apache.ibatis.session.SqlSession;import com.home.entity.Student;import com.home.entity.Teacher;public class TestApp {    public static void main(String[] args) throws IOException {        // 我将获取session的代码封装成了一个工具类，直接用工具类来获取session        SqlSession session = SessionUtils.getSession("mybatis.xml");        String loadTeacher="com.home.entity.teacherMapper.loadTeacher";        String loadStudent="com.home.entity.studentMapper.loadStudent";        Teacher teacher = session.selectOne(loadTeacher,1);        Student student = session.selectOne(loadStudent,1);        System.out.println(student);        System.out.println(teacher);        // 将数据属性到数据中去        session.commit();        // 关闭session        session.close();    } }

5.结果

Student [student_id=4, student_name=hpc, student_number=1, student_teacher=Teacher [teacher_id=1, teacher_name=王老师, teacher_number=1, teacher_student=[]]]Teacher [teacher_id=1, teacher_name=王老师, teacher_number=1, teacher_student=[Student [student_id=5, student_name=zll, student_number=2, student_teacher=null], Student [student_id=4, student_name=hpc, student_number=1, student_teacher=null]]]