java - 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，使用 getMessage 选择和映射事件的消息。但是我在 MessageMapper 中已经有相同的方法 selectById，那么可以重用它吗？

Answer 1

为了使用其他映射器的任何定义(包括语句或 ResultMap)，您应该将映射器的命名空间(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 MessageMapper 位于 com.company.app.mappers 包中，则为:

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 = "com.company.app.mappers.MessageMapper.getMessage"))
    })
    List<Event> selectInInterval(@Param("from") Date from, @Param("to") Date to);
}