demo/src/main/resources/mapping/mybatis.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.demo.dao.UserDao">

<select id="findUserByUserId" parameterType="String" resultType="com.demo.pojo.User">
	select * from user_t t where t.user_id = #{id}
</select>
<update id="updateUsername" parameterType="com.demo.pojo.User">
	update user_t t set t.username = "haha" where t.user_id = 1
</update>

<select id="findUserByUsername" resultType="com.demo.pojo.User">
	select * from user_t t where t.username = #{username}
</select>

<select id="findRolesByUsername" parameterType="String" resultType="java.lang.String">
	select r.role from role_t r,user_role_t ur, user_t u where r.role_id = ur.role_id and ur.user_id = u.user_id and u.username = #{username}
</select>

<select id="findPermissionsByUsername" resultType="java.lang.String">
	select p.permission from role_t r,user_role_t ur, user_t u, permission_t p, role_permission_t rp where r.role_id = ur.role_id and ur.user_id = u.user_id and r.role_id = rp.role_id and rp.permission_id = p.permission_id and u.username  = #{username}
</select>

<insert id="insertUserInfo" parameterType="com.demo.pojo.User">
	<selectKey resultType="java.math.BigDecimal" order="BEFORE" keyProperty="id">
		selet squence.nextval as userId from dual
	</selectKey>
	insert into user_t(id, username) values(#{userId}, #{username})
</insert>
</mapper>