refactor code

src/main/resources/mapper/book/ExpressCompanyDao.xml

@@ -0,0 +1,8 @@
+<?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.peanut.modules.book.dao.ExpressCompanyDao">
+    <select id="getExpressCompanyList" resultType="com.peanut.modules.book.vo.ExpressCompanyVo">
+        select name, code from express_company
+    </select>
+</mapper>