<insert id="insertitem" parameterType="cn.qkp.po.user">
INSERT INTO user(username,birthday,sex,address) VALUES(#{username},#{ birthday},#{sex},#{address})
</insert>

 @Test
 public void start3(){
  SqlSession session = sqlsessionfactory.openSession();//打开SqlSession
  User user = new User();//创建实体对象
  user.setUsername("mylydg");
  user.setSex("1");
  user.setBirthday(new Date());
  session.insert("test.insertUser", user);//执行插入
  session.commit();//提交事务
  session.close();//关闭连接
 }

<insert id="insertitem" parameterType="cn.qkp.pojo.user">
<!-- 1、语句select LAST_INSERT_ID()为查找最后插入元素的id
  2、order属性表示相对insert语句在什么时候执行，有两个参数"AFTER"之后和"BEFORE"之前
  3、resultType属性表示返回值的类型
  4、keyProperty表示返回到的属性，切记要与insert中的parameterType类型的值相同，它会把值返回给parameterType对象
 -->
<selectKey order="AFTER" resultType="int" keyProperty="id"> 
select LAST_INSERT_ID()
</selectKey>

@Test
 public void start3(){
  SqlSession session = sqlsessionfactory.openSession();//打开SqlSession
  User user = new User();//创建实体对象
  user.setUsername("mylydg");
  user.setSex("1");
  user.setBirthday(new Date());
  session.insert("test.insertUser", user);//执行插入
  session.commit();//提交事务
  session.close();//关闭连接
  System.out.println("the id ="+user.getId());//获得主键并打印
 }

 <update id="update" parameterType="cn.qkp.mybatis.po.User">
 update user set username = #{username},sex = #{sex},birthday = #{birthday},address = #{address} where id=#{id}
 </update>

 @Test
 public void update(){
  //通过工厂类打开数据接口
  SqlSession sqlsession = sqlsessionfactory.openSession();
  //设置接收对象
  User user = new User();;
  user.setUsername("mylydg");
  user.setSex("1");
  user.setBirthday(new Date());
  user.setAddress("the address");
  user.setId(27);
  try {
   //查询数据selectOne为查询一条的方法第一个参数是user.xml中的namespace.id；第二个参数是user配置文件中的#{id}
   sqlsession.update("test.update", user);
   sqlsession.commit();
  } catch (Exception e) {
   // TODO: handle exception
  }finally{
   sqlsession.close();//读完要关闭sqlsession
  }
   System.out.println("the id ="+user.getId());//打印输出
 }

 <delete id="delete" parameterType="int">
 delete from user where id = #{id}
 </delete>

 @Test
 public void delete(){
  //通过工厂类打开数据接口
  SqlSession sqlsession = sqlsessionfactory.openSession();
  try {
   //查询数据selectOne为查询一条的方法第一个参数是user.xml中的namespace.id；第二个参数是user配置文件中的#{id}
   sqlsession.delete("test.delete", 27);
   sqlsession.commit();
  } catch (Exception e) {
   // TODO: handle exception
  }finally{
   sqlsession.close();//读完要关闭sqlsession
  }