浮雨 浮雨
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跪求大神帮忙,servlet出现空指针异常,数据不能修改,急急急 listEmpServlet: package web; import java.io.IOException;import java.io.PrintWriter;import java.sql.Connection;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement; import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse; public class ListEmpServlet extends HttpServlet{ public void service(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{ //访问数据库 Connection conn=null; try{ Class.forName("com.mysql.jdbc.Driver"); conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/jd1109db2", "root", "123"); Statement stat=conn.createStatement(); ResultSet rst=stat.executeQuery("select * from t_emp"); //使用查询得到的结果,生成一个表格 response.setContentType("text/html;charset=utf-8"); PrintWriter out=response.getWriter(); out.println("<table border='1'"+"width='60%'"+"cellpadding='0'"+"cellspacing='0'"); out.println("<tr>"+ "<td>id</td>"+ "<td>姓名</td>"+ "<td>薪水</td>"+ "<td>年龄</td></tr>"); while(rst.next()){ long id=rst.getLong("id"); String name=rst.getString("name"); double salary=rst.getDouble("salary"); int age=rst.getInt("age"); out.println("<tr><td>" +id+"</td><td>" +name+"</td><td>" +salary+"</td><td>" +age+"</td><td>"+"<a href='del?id="+id+"'>"+"删除</a>"+"&nbsp;"+"<a href='load?id="+id+"'>"+"修改</a></td></tr>"); } out.println("</table>"); out.println("<a href='addEmp.html'>"+"增加成员</a>"); out.close(); } catch(Exception e){ e.printStackTrace(); throw new ServletException(e); } finally{ if(conn!=null){ try{ conn.close(); } catch(SQLException e){ e.printStackTrace(); } } } }} ModifyEmpServlet: package web; import java.io.IOException;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.SQLException; import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse; public class ModifyEmpServlet extends HttpServlet{ public void service(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{ request.setCharacterEncoding("utf-8"); long id=Long.parseLong(request.getParameter("id")); String name=request.getParameter("name"); double salary=Double.parseDouble(request.getParameter("salary")); int age=Integer.parseInt(request.getParameter("age")); //访问数据库 Connection conn=null; try{ Class.forName("com.mysql.jdbc.Driver"); conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/jd1109db2","root","123"); PreparedStatement prep=conn.prepareStatement("update t_emp set name=?,salary=?,age=? where id=?"); prep.setString(1, name); prep.setDouble(2, salary); prep.setLong(3, age); prep.setLong(4, id); prep.executeUpdate(); response.sendRedirect("list"); } catch(Exception e){ e.printStackTrace(); throw new ServletException(e); } finally{ if(conn!=null){ try{ conn.close(); } catch(SQLException e){ e.printStackTrace(); } } } }} 异常情况是这: 五月 03, 2013 8:28:56 下午 org.apache.catalina.core.StandardWrapperValve invokeSEVERE: Servlet.service() for servlet modifyEmpServlet threw exceptionjava.lang.NullPointerExceptionat sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1008)at java.lang.Double.parseDouble(Double.java:540)at web.ModifyEmpServlet.service(ModifyEmpServlet.java:19)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.Http11Processor.process(Http11Processor.java:859)at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)at java.lang.Thread.run(Thread.java:722) 数据能增删,修改只能打开页面,却不能修改,跪求大神帮忙啊
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