我们根据上篇文章搭建的mybatis环境操作，如果没有搭建环境的可以去上篇博客(第一个mybatis程序)查看。
1、namespace
namespace中的包名要和Dao/mapper接口的包名一致!
2、select
选择，查询语句;
id：就是对应的namespace中的方法名;
resultType：Sql语句执行的返回值!
parameterType：参数类型!
1、编写接口
//根据id查询用户 User getUserById(int id);
2、编写mapper中对应的sql语句
<select id = "getUserById" resultType="com.allen.pojo.User" parameterType = "int">
select * from mybatis.user where id = #{id};
</select>3、测试
@Test
public void getUserById(){
SqlSession sqlSession = MybatisUtils.getSqlSession();
UserDao userDao = sqlSession.getMapper(UserDao.class);
User user = userDao.getUserById(1);
System.out.println(user);
sqlSession.close();
}
3、insert
插入，新增语句
//新增用户 int addUser(User user);
<insert id = "addUser" parameterType = "com.allen.pojo.User">
insert into mybatis.user(`id`, `name`, `pwd`) values (#{id}, #{name}, #{pwd});
</insert>@Test
public void addUser(){
SqlSession sqlSession = MybatisUtils.getSqlSession();
UserDao userDao = sqlSession.getMapper(UserDao.class);
int allen = userDao.addUser(new User(4, "allen", "123456"));
if(allen > 0){
System.out.println("新增成功");
sqlSession.commit();
}
sqlSession.close();
}
4、update
修改，更新语句
//修改用户 int updateUser(User user);
<update id = "updateUser" parameterType="com.allen.pojo.User">
update mybatis.user set `name` = #{name}, `pwd` = #{pwd} where id = #{id};
</update>@Test
public void updateUser(){
SqlSession sqlSession = MybatisUtils.getSqlSession();
UserDao userDao = sqlSession.getMapper(UserDao.class);
int liqinglin = userDao.updateUser(new User(4, "liqinglin", "654321"));
if (liqinglin > 0){
System.out.println("修改成功");
sqlSession.commit();
}
sqlSession.close();
}
5、delete
删除语句
//删除用户 int deleteUser(int id);
<delete id = "deleteUser" parameterType = "int">
delete from mybatis.user where id = #{id};
</delete>@Test
public void deleteUser(){
SqlSession sqlSession = MybatisUtils.getSqlSession();
UserDao userDao = sqlSession.getMapper(UserDao.class);
int i = userDao.deleteUser(4);
if(i > 0){
System.out.println("删除成功");
sqlSession.commit();
}
sqlSession.close();
}
注意：insert、update、delete要提交事务：sqlSession.commit();