MyBatis alias configuration

MyBatis alias configuration

In sqlMapConfig.xml files often have to configure a lot of bean, the following code:

 <!--别名配置-->
    <typeAliases>
        <!--type：指的使需要配置的代码，alias：指定一个别名，建议使当前类-->
        <typeAlias type="com.***.mybatis.bean.Student" alias="student"></typeAlias>
  
    </typeAliases>

But often these classes in the bean directory, so MyBatis launched a package scanning this property, as follows

  <!--别名配置-->
    <typeAliases>
        <!--指定包名，指定后，别名默认就是包下的类名-->
        <package name="com.***.mybatis.bean"/>
    </typeAliases>

This eliminates the need to prepare excessive <typeAlias> </ typeAlias>, and the lower dao corresponding mapper can directly reference the file, such as the following is written directly in the resultType the student class, and case insensitive

 <!--查询所有学生-->
 <!--id:接口中类方法名，resultType：结果集的返回类型-->
    <select id="findAll" resultType="student">
        select * from tb_stu;
    </select>

But there are still many mapper.xml to be configured,
and in order not to repeat the configuration file Mapperxml, we can write

    <mappers>
        <!--当前包需要和mapper接口类所在包同名，并且当前包需要一级一级创建-->
        <package name="com.houpu.mybatis.mapper"/>
<!--        <mapper resource="mapper/StudentMapper.xml"></mapper>-->
    </mappers>

And often we are so configured, wasted too much time, development efficiency will be much slower

    <mappers>
      <mapper resource="mapper/StudentMapper.xml"></mapper>
    </mappers>

But one thing to note: when referencing mapper.xml hierarchy to Dao and Mapper is to be consistent,
and the packet to create a level as follows:

Mapper files in three directories, so the xml files have the same; as follows:

such references will succeed! ! !

Finally write about, reference sql configuration file
to create a new file the following documents:

db.driverName=com.mysql.cj.jdbc.Driver
db.url=jdbc:mysql:///数据库名
db.username=账号
db.password=密码

In sqlMapConfig.xml file as follows:

 <!--配置properties读取外部文件，注意：上下顺序-->
    <properties resource="file的路径名"></properties>
 <!--配置环境-->
    <environments default="abc">//default随便编写
        <!--环境中定义了，要访问的数据库连接池，事务管理类型-->
        <environment id="abc">
            <transactionManager type="JDBC"></transactionManager>
            <!--数据库连接池-->
            <dataSource type="POOLED">
                <property name="driver" value="${db.driverName}"/>
                <property name="url" value="${db.url}"/>
                <property name="username" value="${db.username}"/>
                <property name="password" value="${db.password}"/>
            </dataSource>
        </environment>
    </environments>

Note that the above files must be written in <configuration> sqlMapConfig.xml file </ configuration> tag