*Mapper.xml中程式碼

<select id="query" parameterType="int" resultType="User">
	select username , password from user where id=#{id}
</select>

主要測試程式碼

User user2 = userMapper.query(7);
System.out.println(user2);
System.out.println(user2.getName() + " " + user2.getPwd());

控制檯輸出user2為null,報錯空指標異常

<select id="query" parameterType="int" resultType="User">
	select username as name, password as pwd from user where id=#{id}
</select>