jsp中传递list对象运行时一直出错,( list=c.Show();运行时,一直提示这句出错,但是java中正常)求解答

package conMysql; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.Statement; public class Conn { private static final String Driver="com.mysql.jdbc.Driver"; private static final String url="jdbc:mysql://localhost:3306/home"; private static final String username="liuhuan"; private static final String password="4826334"; private static Connection conn=null; static{ try { Class.forName(Driver); } catch (ClassNotFoundException e) { e.printStackTrace(); System.out.println("驱动加载失败!"); } } public static Connection getConnection() throws Exception{ if (conn==null) { conn=DriverManager.getConnection(url, username, password); return conn; } return null; } //以下为测试代码 // public static void main(String[] args) throws Exception { // Connection conn=Conn.getConnection(); // if (conn!=null) { // System.out.println("数据库连接正常!"); // Statement stat=conn.createStatement(); // ResultSet rs=stat.executeQuery("select * from HomePage"); // while (rs.next()) { // System.out.println(rs.getString("Name")); // // } // } // else { // System.out.println("数据库连接异常!"); // } // } //以上为测试代码 } package entity; public class Page { private String webName; public String getWebName() { return webName; } public void setWebName(String webName) { this.webName = webName; } } package model; import entity.Page; import conMysql.Conn; import java.awt.List; import java.sql.Connection; import java.sql.ResultSet; import java.sql.Statement; import java.util.ArrayList; public class PageOut { Connection conn; public ArrayList<Page> Show() throws Exception{ Conn c=new Conn(); conn=c.getConnection(); Statement stat=conn.createStatement(); ResultSet rs=stat.executeQuery("select * from Homepage"); ArrayList<Page> list=new ArrayList<Page>(); while (rs.next()) { Page p=new Page(); p.setWebName(rs.getString("Name")); list.add(p); } return list; } } <%@page import="entity.Page"%> <%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%> <%@ page import="entity.Page,model.PageOut,java.util.ArrayList" %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>导航</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page">  </head> <% PageOut c=new PageOut(); ArrayList<Page> list=new ArrayList<Page>(); list=c.Show(); %> <body> <table align="center" bordercolor="green"> <% int i=0; if(i<list.size()){ %> <tr> <% for(;i%20!=0;i++){ %> <td><%list.get(i).getWebName();%></td> <%} %> </tr> <% }%> </table> </body> </html>

怎么没贴错误代码呢不过你Conn这个类里的getConnection()方法的最后一个return返回的应该是conn而不应该是null。

jsp中传递list对象运行时一直出错,( list=c.Show();运行时,一直提示这句出错,但是java中正常)求解答

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