rscount.getInt(1)注意方法

public int doGetNewsNum() throws Exception{
            int rscountInt=0;
            ResultSet rscount=null;
            String sqlcount="select count(*) from news ";
            try{
            PreparedStatement psmtcount=conn.prepareStatement(sqlcount);
            rscount = psmtcount.executeQuery();
            }catch(SQLException e){
                String error="SQLException";
                throw new Exception(error);
            }catch(Exception e){
                String error="Exception";
                throw new Exception(error);
            }
            rscountInt=rscount.getInt(1);
            return rscountInt;
        }

 

报错

严重: Servlet.service() for servlet jsp threw exception

java.sql.SQLException: Before start of result set

at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1073)

at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987)

at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:982)

at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:927)

at com.mysql.jdbc.ResultSetImpl.checkRowPos(ResultSetImpl.java:841)

at com.mysql.jdbc.ResultSetImpl.getInt(ResultSetImpl.java:2672)

at data.News.doGetNewsNum(News.java:40)

at org.apache.jsp.testjdbc_jsp._jspService(testjdbc_jsp.java:94)

at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)

at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)

at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)

at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)

at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)

at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)

at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)

at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)

at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)

at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:859)

at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:579)

at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1555)

at java.lang.Thread.run(Thread.java:619)

原因：

RESULTSET在没进行操作是在第一条数据之前的，所以才有before start，你应该调用next（）方法，移动到第一条数据。

 

修改方法：

 

public int doGetNewsNum() throws Exception{
            int rscountInt=0;
            ResultSet rscount=null;
            String sqlcount="select count(*) from news ";
            try{
            PreparedStatement psmtcount=conn.prepareStatement(sqlcount);
            rscount = psmtcount.executeQuery();
            }catch(SQLException e){
                String error="SQLException";
                throw new Exception(error);
            }catch(Exception e){
                String error="Exception";
                throw new Exception(error);
            }
            rscount.next();
            rscountInt=rscount.getInt(1);
            return rscountInt;
        }

增加 rscount.next()