1. 步骤：

• (1). 加包
• (2). 编写db.properties；编写conf.xml，将db.properties加入到conf.xml；引入别名
• (3). 建立实体类
• (4). 编写sql操作对应的***Mapper.xml文件
• (5). 将sql操作对应的***Mapper.xml文件注册到conf.xml文件中
• (6). 编写MyBaitsUtils
• (7). 测试

2. 详细步骤

• (1). 加包

　　

• (2). 编写db.properties；

driverClass=com.mysql.jdbc.Driverurl=jdbc:mysql://localhost:3306/mybatis1username=rootpassword=lfdy

• 编写conf.xml，将db.properties加入到conf.xml；

• 引入别名

• (3). 建立实体类

package com.atguigu.mybatis.domain;import java.util.List;/** * @author hp * */public class Classes {        private int id;    private String name;    private Teacher teacher;    private List
      
        students;    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 Teacher getTeacher() {        return teacher;    }    public void setTeacher(Teacher teacher) {        this.teacher = teacher;    }    public List
       
         getStudents() {        return students;    }    public void setStudents(List
        
          students) {        this.students = students;    }    public Classes(int id, String name, Teacher teacher, List
         
           students) {        super();        this.id = id;        this.name = name;        this.teacher = teacher;        this.students = students;    }    public Classes() {        super();    }    @Override    public String toString() {        return "Classses [id=" + id + ", name=" + name + ", teacher=" + teacher + ", students=" + students + "]";    }    }
         
        
       
      

package com.atguigu.mybatis.domain;/** * @author hp * */public class Teacher {    private int id;    private String 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 Teacher(int id, String name) {        super();        this.id = id;        this.name = name;    }    public Teacher() {        super();    }    @Override    public String toString() {        return "Teacher [id=" + id + ", name=" + name + "]";    }    }

package com.atguigu.mybatis.domain;/** * @author hp * */public class Student {        private int id;    private String 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 Student(int id, String name) {        super();        this.id = id;        this.name = name;    }    public Student() {        super();    }    @Override    public String toString() {        return "Student [id=" + id + ", name=" + name + "]";    }    }

• (4). 编写sql操作对应的***Mapper.xml文件

      
     
       　　
          
              select * from class c,teacher t,student s where c.teacher_id = t.t_id and c.c_id = s.class_id and c.c_id = #{id}            
              
               
               
                   
                    
                
                       
                   
                    
                
           
      
     

　　　　　　　　

      <!-- 嵌套chaxun查询 -->

　　　　<select id="getClass2" parameterType="int" resultMap="ClassResultMap2">

　　　　　　　　select * from class where c_id = #{id}

　　　　</select>

　　　　<resultMap type="Classes" id="ClassResultMap2">

　　　　　　<id property="id" column="c_id"/>

　　　　<result property="name" column="c_name"/>

　　　　<association property="teacher" column="teacher_id" javaType="Teacher" select="getTeacher2"/>

　　　　<collection property="students" column="c_id" ofType="Student" select="getStudent2"/>

　　　　</resultMap>

　　　　<select id="getTeacher2" parameterType="int" resultType="Teacher">

　　　　　　select t_id id,t_name name from teacher where t_id=#{id}

　　　　</select>

　　　　<select id="getStudent2" parameterType="int" resultType="Student">

　　　　　　select s_id id,s_name name from student where class_id=#{id}

　　　　</select>

• (5). 将sql操作对应的***Mapper.xml文件注册到conf.xml文件中

• (6). 编写MyBaitsUtils

package com.atguigu.mybatis.test;import java.io.InputStream;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;public class MyBatisUtils {        public static SqlSessionFactory getFactory(){        String resource = "config.xml";                InputStream is = MyBatisUtils.class.getClassLoader().getResourceAsStream(resource);                SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);                    return factory;    }}

• (7). 测试

package com.atguigu.mybatis.test;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import com.atguigu.mybatis.domain.*;/** * @author hp * */public class MyBatisTest {        public static void main(String[] args) {                SqlSessionFactory factory = MyBatisUtils.getFactory();                SqlSession session = factory.openSession();                String statement = "com.atguigu.mybatis.mapper.ClassMapper.getClass";            Classes c=  (Classes) session.selectOne(statement,1);        System.out.println(c);                session.close();            }}