请教在连接MYSQl时出现了连接问题,请大侠们救一下小弟,万分感谢!!!!!!

Question

小弟做一个在线书店的系统.
用的是J2EE+Tomcat 5.0 +mysql4.1 
小第在首页index.jsp登陆界面输入数据库中已经存在的用户名wxy,密码wxy提交表单转到login.jsp.
但是却出现了:
root cause: 
java.lang.NullPointerException
bookshop.run.login.excute(login.java:65)
org.apache.jsp.bookshop.login_jsp._jspService(login_jsp.java:71)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
在Tomcat 端出现了db  connect error:
index.jsp 源代码如下:
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<%@ page import="java.util.*" %>
<%@ page session="true" %>
<%@include file="/bookshop/inc/head.inc"%>
<br>  <form name="form1" method="post" action="login.jsp">
          <div align=center>用户登录 </div>
          <br>          
          <table width="300" border="0" cellspacing="1" cellpadding="1" align="center">
          <br>
            <tr> 
              <td align="right">用户名：</td>
              <td> 
                <input type="text" name="username" size="15" maxlength="25">
              </td>
            </tr>
            <tr> 
              <td align="right">密码：</td>
              <td> 
                <input type="password" name="passwd" size="15" maxlength="20">
              </td>
            </tr>
            <tr> 
              <td colspan="2" align="center"> 
                <input type="submit" name="Submit" value="登录">
              
                <input type="reset" name="Submit2" value="取消">
              </td>
            </tr>
             <tr>     
            <td colspan="2" align="center">
          <p>&nbsp;</p>
            测试用户：wxy 密码：wxy 
       </td>
        </tr>
            <tr> 
              <td colspan="2" align=center>如果不是本站会员，请在此<a href="reg.jsp">注册</a>。</td>              
            </tr>
         </table>
   </form><%@include file="/bookshop/inc/tail.inc"%>

Answer 1

另外login.jsp 源代码如下:
<%@ page session="true" %>
<jsp:useBean id="login" scope="page" class="bookshop.run.login" />
<%
String mesg = "";if( request.getParameter("username")!=null && !request.getParameter("username").equals("")){
String username =request.getParameter("username");
String passwd = request.getParameter("passwd");
username = new String(username.getBytes("ISO8859-1"));
passwd = new String(passwd.getBytes("ISO8859-1"));
login.setUsername(username);
login.setPasswd(passwd);
out.print(username+passwd);
if (login.excute()){
session.setAttribute("username",username);
String userid = Long.toString(login.getUserid());
session.setAttribute("userid",userid);
response.sendRedirect("booklist.jsp");
%>
<%
}else {
mesg = "登录出错！" ;
}
}
%>
<%@include file="/bookshop/inc/head.inc"%><script language="javascript"> function checkform() {
if (document.form1.username.value=="" || document.form1.passwd.value==""){
alert("用户名或密码为空！");
return false;
}
return true;  }</script>
<div align=center>用户登录 </div>
          <br>          
<% if (!mesg.equals("")){
out.println("<p>" + mesg + "</p>");}%>

  <form name="form1" method="post" action="login.jsp">
    <table width="400" border="0" cellspacing="1" cellpadding="1" align="center">
    <tr> 
      <td width="147" align="right">用户名：<br>
      </td>
      <td width="246" valign="top">
          <input type="text" name="username" size="16" maxlength="25">
        </td>
    </tr>
    <tr> 
      <td width="147" align="right">密码：</td>
      <td width="246" valign="top">
          <input type="password" name="passwd" maxlength="20" size="16">
        </td>
    </tr>
    <tr> 
      <td width="147" align="right">&nbsp;</td>
      <td width="246" valign="top">
          <input type="submit" name="Submit" value="登录" onclick="javascript:return(checkform());">
          <input type="reset" name="Submit2" value="取消">
        </td>
    </tr>
    <tr>     
      <td colspan="2" align="center">
        <p>&nbsp;</p>
        测试用户：wxy 密码：wxy
      </td>
    </tr>
    <tr> 
    
      <td colspan="2" align="center">
        <p>&nbsp;</p>
        <p>如果你还不是本站用户，请在此<a href="reg.jsp">注册</a></p>
      </td>
    </tr>
  </table>
    </form>
 <%@include file="/bookshop/inc/tail.inc"%>

Answer 2

DataBase.java原代码如下:
package bookshop.util;
/**
 * <p>数据库连接专用包 </p>
 * <p>Copyright: wxy Copyright (c) 2004</p>
 * <p>Company:juanjuan book shop online </p>
 * @by :wxy
 * @version 1.0
 */
import java.sql.*;
public class DataBase {
  public Connection conn;
  public Statement stmt;
  public ResultSet rs=null;
  public String sqlStr="";  public DataBase() {
    this.connect();
  }
 public boolean connect(){
      try{
        Class.forName("org.gjt.mm.mysql.Driver").newInstance();
        String url ="jdbc:mysql://localhost:3306/BookStore?user=root&password=&characterEncoding=8859_1";
        conn=DriverManager.getConnection(url);
        stmt = conn.createStatement ();
       }catch(Exception ee){
        System.out.println("connect db error:"+ee.getMessage());
        return false;
       }
      return true;
    }
 public static void main(String[] args) {
     try{
            DataBase db = new DataBase();
            db.connect();
          }catch(Exception e){
            e.printStackTrace();
          }
        }
}

Answer 3

login.java原代码如下:
package bookshop.run;
/**
 * <p>管理用户登录的类 </p>
 */
import bookshop.util.*;
public class login extends DataBase {
        private String username; //登录用户名
        private String passwd; //登录密码
        private boolean isadmin; //是否管理员登录
        private long userid=0; //用户ID号
        public login() throws Exception{
                super();
                username = "";
                passwd = "";
                isadmin = false;
        }
        public String getUsername() {
                return username;
        }
        public void setUsername(String newusername) {
                username = newusername;
        }
        public String getPasswd() {
                return passwd;
        }
        public void setPasswd(String newpasswd) {
                passwd = newpasswd;
        }
        public boolean getIsadmin() {
                return isadmin;
        }
        public void setIsadmin(boolean newIsadmin) {
                isadmin = newIsadmin;
        }
        public long getUserid() {
                return userid;
        }
        public void setUserid (long uid) {
                userid = uid;
        }
        /**
         * 获得查询用户信息的sql语句
         * @return
         */
        public String getSql() {
                if (isadmin) {
                        sqlStr = "select * from BookAdmin where adminuser = '" +
                            dataFormat.toSql(username) + "' and adminpass = '" +
                            dataFormat.toSql(passwd) + "'";
                }else {
                        sqlStr = "select * from shop_user where username = '" +
                            username + "' and password = '" + passwd + "'";
                }
                return sqlStr;
        }
        /**
         * 执行查询
         * @return
         * @throws java.lang.Exception
         */
        public boolean excute() throws Exception {
                boolean flag = false;
                DataBase db = new DataBase();
                db.connect();
           stmt = db.conn.createStatement ();
           rs = stmt.executeQuery(getSql());
                if (rs.next()){
                        if (!isadmin)
                        {
                                userid = rs.getLong("id");
                        }
                        flag = true;
                }
                rs.close();
                return flag;
        }
};

Answer 4

感觉应该是你的MYSQL安全访问问题吧，也就是必须要用户密码

Answer 5

感谢我改为有密码,重新测试发现又出现如下错误:
exception org.apache.jasper.JasperException: Unable to compile class for JSPGenerated servlet error:
C:\Tomcat 5.0\work\Catalina\localhost\_\org\apache\jsp\bookshop\booklist_jsp.java:627: handlePageException(java.lang.Exception) in javax.servlet.jsp.PageContext cannot be applied to (java.lang.Throwable)
        if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
                                                          ^
Generated servlet error:
Note: C:\Tomcat 5.0\work\Catalina\localhost\_\org\apache\jsp\bookshop\booklist_jsp.java uses unchecked or unsafe operations.
Generated servlet error:
Note: Recompile with -Xlint:unchecked for details.
1 error org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:84)
org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:332)
org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:412)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:472)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:451)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:439)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:511)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:295)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)说明一下book_list为login.jsp 导向的jsp page.