mybatis entry --day01: configured via annotations

1. Attach a copy of a copy of improvement (notes). Due to the configuration using annotations, so no xml, and delete the resources in the file com

Here's what com in IUserDao.xml inside:

<?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.itheima.dao.IUserDao">
    <!--配置查询所有-->
    <select id="findAll" resultType="com.itheima.domain.User">
        select * from user
    </select>
</mapper>

---

Because deleted IUserDao.xml, so the location of the configuration file of the master configuration file to specify the mapping disappeared:

    <!--指定映射配置文件的位置，映射配置文件指的是每个dao独立的配置文件-->
    <mappers>
        <mapper resource="com/itheima/dao/IUserDao.xml"/>
    </mappers>

It needs to be changed:

    <!--指定映射配置文件的位置，映射配置文件指的是每个dao独立的配置文件-->
    <!--如果是用注解来配置，此处应该使用class属性指定被注解的dao全限定类名-->
    <mappers>
        <mapper class="com.itheima.dao.IUserDao"/>
    </mappers>

---

Because deleted IUserDao.xml, so the need to re-write the query. Join @Select ( "select * from user") in IUserDao interface.

public interface IUserDao {

    //查询所有操作
    @Select("select * from user")
    List<User> findAll();
}

Then run, it is still feasible.

2. A summary of 1

The xml configuration to configuration steps Notes:
① delete mapping configuration file resources in IUserDao.xml
② mappers will master the contents of the configuration file to read:

	<mappers>
        <mapper class="com.itheima.dao.IUserDao"/>
    </mappers>

I.e. mappers in the main configuration file attribute is used to specify the fully qualified class name of the class dao interface.
Add query ③ using annotations in IUserDao interface mode:

public interface IUserDao {

    //查询所有操作
    @Select("select * from user")
    List<User> findAll();
}