在Mybatis @Select注解中实现拼写动态sql

现在随着mybatis plus的应用，越来越多的弱化了SQL语句，对于单表操作可以说几乎不需要进行自己编写SQL语句了，但对于多表查询操作目前mybatis plus还没有很好的支持，还需要自己编写SQL语句，如：

import java.util.List; 
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
 
import com.baomidou.mybatisplus.mapper.BaseMapper;
import com.shield.base.model.domain.MenuDO;
import com.shield.base.model.param.MenuTreeParam;
 
/**
 * 基础数据操作对象
 *
 * @author xxx
 * @date 2018/5/18
 */
@Mapper
public interface MenuDAO extends BaseMapper {
 
 /**
  * 根据菜单编码获得所有下级菜单列表(包括本级)
  * @param menuId 菜单编码
  * @return 该菜单下的所有菜单列表(包括本级)
  */
 @Select("WITH menuTree"
  + " AS"
  + "("
  + " SELECT menu1.father_rowid as id,menu1.son_rowid as parentId,menu1.system_name as menuName,"
  + "menu1.system_full_rowid as menuTreeFlat,menu1.level_value as menuLevel,menu1.homepage_status as homeStatus,"
  + "menu1.menu_status as menuType,menu1.sort as sort,menu1.duty_name as createName,"
  + "menu1.duty_datetime as createDate,menu1.update_datetime as updateDate,menu1.stop_status as status"
  + " FROM system_menu_setup menu1 WHERE menu1.father_rowid = #{menuId}"
  + " UNION ALL"
  + " SELECT menu2.father_rowid as id,menu2.son_rowid as parentId,menu2.system_name as menuName,"
  + "menu2.system_full_rowid as menuTreeFlat,menu2.level_value as menuLevel,menu2.homepage_status as homeStatus,"
  + "menu2.menu_status as menuType,menu2.sort as sort,menu2.duty_name as createName,"
  + "menu2.duty_datetime as createDate,menu2.update_datetime as updateDate,menu2.stop_status as status"
  + " FROM system_menu_setup menu2"
  + " INNER JOIN menuTree T ON menu2.son_rowid = T.id"
  + ")"
  + " SELECT id,parentId,menuName,MenuTreeFlat,menuLevel,homeStatus,menuType,sort,createName,"
  + "createDate,updateDate,status FROM menuTree")
 List selectMenuTreeList(@Param(value = "menuId") Long menuId); 
}

这样整个语句基本上都是写死的,没有办法通过参数动态拼接SQL语句，在对于 相同语句不同参数来拼接SQL语句是十分不便的,而如果使用xml来配置的话可以用

 
 and menu.stop_status=#{stopStatus} and roleMenu.stop_status=#{stopStatus}
 
 
 and menuSource.menu_source=#{menuSource}
 
 
 and roleUser.operator_rowid=#{userId}
 

但是现在很多公司可能会采用@Select注解方式来编写SQL语句，而非通过xml 的SQL Mapper，那对于@Select这种该如何做呢？其实很简单，只是需要用") List selectMenuTreeListByUserId(MenuTreeParam menuTreeParam); }

至此我们就可以像在xml文件里面一样愉快的动态拼接你想要的SQL语句了！

注意：

在@Select注解中采用