【MyBatis】如何配置Mapper

Java doesn’t really provide any good means of auto-discovery in this regard, so the best way to do it is to simply tell MyBatis where to find the mapping files.
於是我們有了<mappers>元素：

<!-- 我們可以寫xml檔案的全限定名 --><mappers>  <mapper resource="org/mybatis/builder/AuthorMapper.xml"/>  <mapper resource="org/mybatis/builder/BlogMapper.xml"/>  <mapper resource="org/mybatis/builder/PostMapper.xml"/></mappers><!-- 當然也可以是介面路徑 --><mappers>  <mapper class="org.mybatis.builder.AuthorMapper"/>  <mapper class="org.mybatis.builder.BlogMapper"/>  <mapper class="org.mybatis.builder.PostMapper"/></mappers><!-- 這才是最霸道的... --><mappers>  <package name="org.mybatis.builder"/></mappers>

如果要把mapper給Spring呢？Scanning for mappers！
我們需要MyBatis-Spring提供的三種方案：

• MyBatis-SpringUsing the <mybatis:scan/> element.
  

• <!-- 基本的... --><mybatis:scan base-package="org.mybatis.spring.sample.mapper" />

  Using the annotation @MapperScan
  

  //喜歡用註解的...@MapperScan("org.mybatis.spring.sample.mapper")

• Using a classic Spring xml file and registering the MapperScannerConfigurer
  The MapperScannerConfigurer is a BeanDefinitionRegistryPostProcessor that can be included in a classic xml application context as a normal bean.

  <!-- 我最喜歡的 --><bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">        <property name="basePackage" value="org.mybatis.spring.sample.mapper" /></bean>

  然後我再也不需要：

  <mappers>    <package name="org.mybatis.spring.sample.mapper"/></mappers>

  另外，當額外需要定義sqlSessionFactory or sqlSessionTemplate時：
  

  Note bean names are used, not bean references. This is because the scanner loads early during the start process and it is too early to build mybatis object instances.

  也就是說：

  <!-- 不是ref是value --><property name="sqlSessionFactoryBeanName" value="sqlSessionFactory" />