/**
     * 判断数据库中是否存在该学号学生
     */
    private boolean isExit(String xh) {
        boolean flag = false;
        XsxxglXsjbxxVOImpl vo =
            (XsxxglXsjbxxVOImpl) ADFUtils.findIterator("XsxxglXsjbxxVO1Iterator").getViewObject(); //学生基本信息vo
        ViewCriteria vc = vo.createViewCriteria();   
        vc.setName("criteria");   
        ViewCriteriaRow vcRow = vc.createViewCriteriaRow();   
        ViewCriteriaItem item = vcRow.ensureCriteriaItem("Xh");   
        item.setOperator("=");   
        item.setValue(xh);   
        vc.add(vcRow);   
        RowIterator it = vo.findByViewCriteria(vc, -1, vo.QUERY_MODE_SCAN_DATABASE_TABLES);  
        if (it.getRowCount() > 0) {   //查询到结果 
            flag = true;
        }
        vo.removeViewCriteria("criteria");  
        return flag;
    }

 查询数据库而不影响vo结果集