为什么我一执行：rs.getInt(1)，就会抛出下面的异常来？？

为什么我一执行：rs.getInt(1)，就会抛出下面的异常来？？
java.sql.SQLException: [Microsoft][SQLServer 2000 Driver for JDBC]Invalid operation for the current cursor position. at com.microsoft.jdbc.base.BaseExceptions.createException(Unknown Source) at com.microsoft.jdbc.base.BaseExceptions.getException(Unknown Source) at com.microsoft.jdbc.base.BaseResultSet.validateCursorPosition(Unknown Source) at com.microsoft.jdbc.base.BaseResultSet.getInt(Unknown Source) at aisite.DataBaseAccessor.CheckUser(DataBaseAccessor.java:74) at aisite.UserLoginBean.userLoginIn(UserLoginBean.java:23) at aisite.userLoginAction.execute(userLoginAction.java:27) at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419) at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224) at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1192) at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:430) at javax.servlet.http.HttpServlet.service(HttpServlet.java:760) at javax.servlet.http.HttpServlet.service(HttpServlet.java:853) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:243) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:190) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.valves.CertificatesValve.invoke(CertificatesValve.java:246) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2347) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:170) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.connector.http.HttpProcessor.process(HttpProcessor.java:1027) at org.apache.catalina.connector.http.HttpProcessor.run(HttpProcessor.java:1125) at java.lang.Thread.run(Thread.java:534)