mybatis 映射器

秒速五厘米 2022-04-24 01:16 159阅读 0赞

mybatis 提供4种方式的映射器，如下图
    
    <mappers>
      <mapper resource="org/mybatis/builder/AuthorMapper.xml"/>
      <mapper resource="org/mybatis/builder/BlogMapper.xml"/>
      <mapper resource="org/mybatis/builder/PostMapper.xml"/>
    </mappers>
    
    
    <mappers>
      <mapper url="file:///var/mappers/AuthorMapper.xml"/>
      <mapper url="file:///var/mappers/BlogMapper.xml"/>
      <mapper url="file:///var/mappers/PostMapper.xml"/>
    </mappers>
    
    
    <mappers>
      <mapper class="org.mybatis.builder.AuthorMapper"/>
      <mapper class="org.mybatis.builder.BlogMapper"/>
      <mapper class="org.mybatis.builder.PostMapper"/>
    </mappers>
    
    
    <mappers>
      <package name="org.mybatis.builder"/>
    </mappers>

说是4种，其实就是2种，一个就是通过解析xml，生成MapperStatement，然后通过xml的namespace属性找到mapper接口，生成mapper接口的代理类，（然后通过mapper接口找同目录下的mapper.xml生成MapperStatement，由于xml在前面解析过，这里不能再次解析）再解析mapper接口方法上的注解，生成MapperStatement。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzM4NTU4MDc2_size_16_color_FFFFFF_t_70][]

一种就是解析mapper接口，生成mapper接口的代理类，然后通过mapper接口找同目录下的mapper.xml生成MapperStatement，再解析mapper接口方法上的注解，生成MapperStatement。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzM4NTU4MDc2_size_16_color_FFFFFF_t_70 1][]

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzM4NTU4MDc2_size_16_color_FFFFFF_t_70 1]: /images/20220221/4ca87fd5edbd4c94b383f8519e05f9d2.png