实体类设置别名（typeAliases）

• MyBatis中别名存在的主要意义就是简化开发

• MyBatis中引用类有三种方式
  1. 直接使用实体类的完整包名
  2. 使用实体类的typeAlias别名
  3. 使用包名作为别名

使用完整包名

<select id="getUserById" parameterType="int" resultType="com.mybatis.pojo.Users">
        select * from smbms_user where id=#{id}
</select>

使用实体类的 typeAlias 别名

• resource/mybatis-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>

 …

<!-- 设置实体类别名 -->

<typeAliases>

<typeAlias type="com.mybatis.pojo.Users" alias="Users"/>

</typeAliases>

</configuration>

• UserMapper.xml

<?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.mybatis.dao.UsersMapper">

<select id="getUserById" parameterType="int" resultType="Users">
        select * from smbms_user where id=#{id}
</select>

…

</mapper>

使用包名作为别名

• resource/mybatis-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>

    <!-- 设置实体类别名 -->

    <typeAliases>

    <package name="com.mybatis.pojo.Users" />

    </typeAliases>

</configuration>

• UserMapper.xml

<?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.mybatis.dao.UsersMapper">

<select id="getUserById" parameterType="int" resultType="Users">
        select * from smbms_user where id=#{id}
</select>

…

</mapper>