hibernate的报错信息a different object with the same identifier value was already associated with the session解决办法

废话不多说,直接说原因,这是在hibernate中,有2个相同类型的实体类具有同样的主键标识符,然后调用update或者调用saveOrUpdate,我朋友出这个错的由于他想要update一条数据时,获取主键时从数据库查询获取,此时接收的对象的主键id是12,吧这个值赋给要更新入参的对象,2个对象的主键就都是12了,所有会报错,

 @Override
     public DTO createExamInfo(DTO dto) {

         Integer examId = GetParamUtil.convertObject(dto.getParam("examId"));
         ExamInfo examInfo=new ExamInfo();
         ExamInfo examInfo = examInfoList.get(0);

         examInfo.setExamId(examId);
         Integer examPaperId = GetParamUtil.convertObject(dto.getParam("examPaperId"));
         examInfo.setExamPaperId(examPaperId);
         String title = GetParamUtil.converObject(dto.getParam("title"));
         examInfo.setTitle(title);
         Integer pattern = GetParamUtil.convertObject(dto.getParam("pattern"));
         examInfo.setPattern(pattern);
         Integer type = GetParamUtil.convertObject(dto.getParam("type"));
         examInfo.setType(type);
         Integer form = GetParamUtil.convertObject(dto.getParam("form"));
         examInfo.setForm(form);
         Integer monitor = GetParamUtil.convertObject(dto.getParam("monitor"));
         examInfo.setMonitor(monitor);
         String isPerpetual = GetParamUtil.converObject(dto.getParam("isPerpetual"));
         examInfo.setIsPerpetual(isPerpetual);
         String startTime = GetParamUtil.converObject(dto.getParam("startTime"));
         examInfo.setStartTime(startTime);
         String endTime = GetParamUtil.converObject(dto.getParam("endTime"));
         examInfo.setEndTime(endTime);
         String examCreateTime = GetParamUtil.converObject(dto.getParam("examCreateTime"));
         examInfo.setExamCreateTime(examCreateTime);
         String createDate = GetParamUtil.converObject(dto.getParam("createDate"));
         examInfo.setCreateDate(createDate);
         examInfo.setIsUsed(0);
         examInfo.setDelFlg("0");
         List<ExamInfo> examInfoList=examInfoDao.findByProperty("examId", examId);
         if (examInfoList!=null&&examInfoList.size()>0) {
             examInfo.setId(examInfoList.get(0).getId());
             examInfoDao.update(examInfo);
         }else{
             examInfoDao.save(examInfo);
         }

         return null;
     }

第33行查出了这条数据,此时会话中包含一个id是12的对象(就是此时想要更新的那条数据的主键),然后35行又把id赋值给了另一个对象,执行update时就会报错,我给他改进了一下代码,如下:

 @Override
     public DTO createExamInfo(DTO dto) {

         Integer examId = GetParamUtil.convertObject(dto.getParam("examId"));
         List<ExamInfo> examInfoList=examInfoDao.findByProperty("examId", examId);
 //        ExamInfo examInfo=new ExamInfo();
         ExamInfo examInfo = examInfoList.get(0);

         examInfo.setExamId(examId);
         Integer examPaperId = GetParamUtil.convertObject(dto.getParam("examPaperId"));
         examInfo.setExamPaperId(examPaperId);
         String title = GetParamUtil.converObject(dto.getParam("title"));
         examInfo.setTitle(title);
         Integer pattern = GetParamUtil.convertObject(dto.getParam("pattern"));
         examInfo.setPattern(pattern);
         Integer type = GetParamUtil.convertObject(dto.getParam("type"));
         examInfo.setType(type);
         Integer form = GetParamUtil.convertObject(dto.getParam("form"));
         examInfo.setForm(form);
         Integer monitor = GetParamUtil.convertObject(dto.getParam("monitor"));
         examInfo.setMonitor(monitor);
         String isPerpetual = GetParamUtil.converObject(dto.getParam("isPerpetual"));
         examInfo.setIsPerpetual(isPerpetual);
         String startTime = GetParamUtil.converObject(dto.getParam("startTime"));
         examInfo.setStartTime(startTime);
         String endTime = GetParamUtil.converObject(dto.getParam("endTime"));
         examInfo.setEndTime(endTime);
         String examCreateTime = GetParamUtil.converObject(dto.getParam("examCreateTime"));
         examInfo.setExamCreateTime(examCreateTime);
         String createDate = GetParamUtil.converObject(dto.getParam("createDate"));
         examInfo.setCreateDate(createDate);
         examInfo.setIsUsed(0);
         examInfo.setDelFlg("0");
         if (examInfoList!=null&&examInfoList.size()>0) {
 //            examInfo.setId(examInfoList.get(0).getId());
             examInfoDao.update(examInfo);
         }else{
             examInfoDao.save(examInfo);
         }

         return null;
     }

直接采用查出数据时接收的对象作为更新时的入参,在这期间给对象set参数,这样从始至终主键为12的对象就只有一个了