MyBatis核心配置文件和映射配置文件的约束头

核心配置文件（sqlMapperConfig.xml）的约束

DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">

映射配置文件（xxx.xml）的约束

DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">