常用jar使用杂记

news/2024/9/18 7:56:41/

dom4j

dom4j的xpath表达式，除了//外都必须从根节点开始写。

hibernate

bag不允许多个平行集合且更新性能低
a different object with the same identifier value was already associated with the session错误
session中有多个同类型对象，地址不一样，id一样，outer-join=“true” 可能会造成a different object with the same identifier value was already associated with the session错误
事务下 hibernate操作和sql操作，不能同时操作一个对象，否则会出现问题。

参数数组的顺序和addScalar顺序调用必须顺序一致

sqlQuery.addScalar("aid", StandardBasicTypes.INTEGER);
sqlQuery.addScalar("minPrice", StandardBasicTypes.DOUBLE);
sqlQuery.addScalar("maxPrice", StandardBasicTypes.DOUBLE);

Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1
线程1：

Member member = MemberUtil.getMember(62392);ClubMember clubMember = ClubMemberUtil.saveMember(null, member);//保存memberId=62392的会员，id=2clubMemberService.saveOrUpdate(clubMember);//又对id=2的进行一次更新，但是id=2的已经被删除了所以会报错。

线程2：

String sql = "SELECT * FROM club_member c WHERE c.member_id = " + memberId;SQLQuery query = getSession().createSQLQuery(sql);query.addEntity(ClubMember.class);@SuppressWarnings("rawtypes")List list = query.list();//因为一些原因（eg.并发保存，没处理好get,set原子性）库里存在memberId=62392的会员，所以返回多个if(list.size() >= 1) {for (int i = 1; i < list.size(); i++) {//删除多余的会员，(id=1,id=2)ClubMember m = (ClubMember) list.get(i);System.out.println("clubmemer------------" + m.getId());delete(m);//删掉了id=2的,即新创建的}return (ClubMember) list.get(0)}return null;

memberId应该是唯一的，如果用唯一索引做限制，则不会有上面问题

懒加载的实现要依赖主键，所以只有从表中的外键可以实现懒加载
Hibernate继承映射:有重复插入问题
java.lang.NoSuchMethodError:An internal error occurred during: “Fetching children of Database”.org.slf4j.spi.LocationAwareLogger.log(Lorg/slf4j/Marker;Ljava/lang/String;ILjava/lang/String;[Ljava/lang/Object;Ljava/lang/Throwable;)V
存在多个slf4j包或没有slf4j包，因而没有找到对应方法，解决方案：删除低版本包或添加slf4j包

mapstruct

org.mapstruct.Mapping 设置批量转换是不起做用的

@Mapper
public interface ExportTaskConverter {//mapping不起作用@Mapping(target = "exportTimeStart", dateFormat =  "yyyy-MM-dd HH:mm:ss")@Mapping(target = "createTime", dateFormat = "yyyy-MM-dd  HH:mm:ss")public List<ExportTaskVo> entityToVo(List<ExportTaskEntity>  entity);public ExportTaskVo entityToVo(ExportTaskEntity entity);
}

改为如下

@Mapper
public interface ExportTaskConverter {//liist会默认调用下面的方法public List<ExportTaskVo> entityToVo(List<ExportTaskEntity>  entity);//起作用@Mapping(target = "exportTimeStart", dateFormat =  "yyyy-MM-dd HH:mm:ss")@Mapping(target = "createTime", dateFormat = "yyyy-MM-dd  HH:mm:ss")public ExportTaskVo entityToVo(ExportTaskEntity entity);
}