1. MyBaits基本概念：略

2. 案例：需求：建立数据库查询，一对一

3.开发步骤：

• (1).建立数据库+表
• (2).加包
• (3).定义实体类
• (4).编写db.properties,将数据库信息写入其中；编写MyBatis的配置文件conf.xml文件，引入db.properties；引入别名
• (5).定义sql映射文件***Mapper.xml文件
• (6).将***Mapper.xml文件注册到conf.xml文件中
• (7).编写MyBaitsUtils工具
• (8).测试

4.代码

　　(1).加包

　　

　　(2). 建立数据库和表

CREATE TABLE teacher(    t_id INT PRIMARY KEY AUTO_INCREMENT,     t_name VARCHAR(20));CREATE TABLE class(    c_id INT PRIMARY KEY AUTO_INCREMENT,     c_name VARCHAR(20),     teacher_id INT);ALTER TABLE class ADD CONSTRAINT fk_teacher_id FOREIGN KEY (teacher_id) REFERENCES teacher(t_id);    INSERT INTO teacher(t_name) VALUES('LS1');INSERT INTO teacher(t_name) VALUES('LS2');INSERT INTO class(c_name, teacher_id) VALUES('bj_a', 1);INSERT INTO class(c_name, teacher_id) VALUES('bj_b', 2);

　　(3). 定义实体类

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

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() {        }    @Override    public String toString() {        return "Teacher [id=" + id + ", name=" + name + "]";    }            }

　  (4). 编写db.properties,将数据库信息写入其中；

username=rootpassword=lfdyjdbcUrl=jdbc:mysql://localhost:3306/mybatis1driverClass=com.mysql.jdbc.Driver

　　编写MyBatis的配置文件conf.xml文件，引入db.properties；

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　　引入别名

　　(5).定义sql映射文件***Mapper.xml文件

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

　　

　　<!-- 方式二：嵌套查询，使用另一个SQL语句来返回预期的复杂类型 -->

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

　　　　select * from class where c_id = #{id}

　　</select>

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

　　　　select t_id id,t_name name from teacher where t_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" select="getTeacher2">

　　　　　　</association>

　　</resultMap>

　　(6). 将***Mapper.xml文件注册到conf.xml文件中

　　(7). 编写MyBaitsUtils工具

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 = "conf.xml";                InputStream is = MyBatisUtils.class.getClassLoader().getResourceAsStream(resource);                SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);                    return factory;    }}

　　(8).测试

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