如何在另一个映射器中重用 MyBatis 的映射器？

Question

我有表event和message，它们具有一对一的关系并由类表示：

public class Event {

    private Long id;

    private Message message;

}

public class Message {

    private Long id;

}

并且有两个映射器：EventMapper和MessageMapper：

public interface EventMapper {

    @Select("SELECT * FROM event WHERE date BETWEEN #{from} AND #{to}")

    @Results({

            @Result(property = "id", column = "id"),

            @Result(property = "message", column = "message_id",

                    javaType = Message.class, one = @One(select = "getMessage"))

    })

    List<Event> selectInInterval(@Param("from") Date from, @Param("to") Date to);

    @Select("SELECT * FROM message WHERE id = #{id}")

    Message getMessage(@Param("id") Long id);

}

public interface MessageMapper {

    @Select("SELECT * FROM message WHERE id = #{id}")

    @Results({

            @Result(property = "id", column = "id"),

            @Result(property = "text", column = "text")

    })

    List<Event> selectById(@Param("id") Long id);

}

EventMapper选择事件并通过注释映射它们，getMessage用于选择和映射事件的消息。但是我已经有相同的方法selectById在MessageMapper，所以是有可能重新使用它？

Answer 1

为了使用来自其他映射器的任何定义，包括语句，或者ResultMap您应该namespace将映射器的（完全限定名称）包含到该实体的标识符中。在您的示例中，假设它MessageMapper在com.company.app.mappers包中，它将是：public interface EventMapper {&nbsp; &nbsp; @Select("SELECT * FROM event WHERE date BETWEEN #{from} AND #{to}")&nbsp; &nbsp; @Results({&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; @Result(property = "id", column = "id"),&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; @Result(property = "message", column = "message_id",&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; javaType = Message.class,&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; one = @One(select = "com.company.app.mappers.MessageMapper.getMessage"))&nbsp; &nbsp; })&nbsp; &nbsp; List<Event> selectInInterval(@Param("from") Date from, @Param("to") Date to);}