注意实体类数据名称要和查询字段名称一样
String sql = null;
sql="select a.tagid,a.datetime,a.value,b.tagname,b.danwei,b.image,b.standvalue from Station"+station+" a left join tagDesc b on a.tagid=b.tagid where a.tagid="+tagid+" and a.datetime =(select MAX(datetime) from Station"+station+" where tagid="+tagid+")";
List<Export> list =this.getSession().createSQLQuery(sql).setResultTransformer(Transformers.aliasToBean(Export.class)).list()