问题解决

1.File–>Settings–>Editor–>File and Code Templates

模板中输入内容

<?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=""></mapper>

再次new，能够看到

成功！！！