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Topic: 一个JavaBean的问题，大家进来看一下！

1.一个JavaBean的问题，大家进来看一下！

Posted by: zrwl
Posted on: 2006-03-22 13:00

各位好~小弟初学JSP+JAVABEAN,在编写一个数据库查询的JavaBean的时候出现了一个问题（使用别的JAVABEAN的时候没问题），望大家指教！我把代码跟错误提示贴出来：
JavaBean代码：
package test;
import java.io.UnsupportedEncodingException;
import java.sql.*;
public class QueryBean
{
  public String query_statement; /*定义SQL语句*/
  public String param[]; /*查询条件*/
  public ResultSet result=null; /*查询结果*/
  public Connection conn;

  //设置查询参数
  public void setParam(String param[])
  {
    this.param=param;
  }

  //设置SQL查询语句
  public void setQueryStatemnet(String query_statement)
  {
    this.query_statement=query_statement;
  }

  //设置连接参数
  public void setConnection(String drivername,String jdbcURL) throws Exception
  {
    Connection conn1;
   Class.forName(drivername);
   conn1=DriverManager.getConnection(jdbcURL);
   conn1.setAutoCommit(false);
   this.conn=conn1;
  }

  //获取查询结果
  public ResultSet getResult()
  {
    try
   {
      PreparedStatement select_stm=conn.prepareCall(query_statement,
          ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
      if(param!=null)
      {
        for(int i=0;i<=param.length;i++)
        {
          select_stm.setString(i+1,param[i]);
          result=select_stm.executeQuery();

        }
      }
     }catch(Exception e){e.printStackTrace();}

     return result;
  }

  //对数据库进行增加记录
  public void insertRecord() throws SQLException,UnsupportedEncodingException
  {
    try
    {
      PreparedStatement insert_stm=conn.prepareStatement(query_statement);
      if(param!=null)
      {
        for(int i=0;i<=param.length;i++)
        {
          insert_stm.setString(i+1,param[i]);
          insert_stm.executeUpdate();
          insert_stm.close();
          conn.commit();
        }
      }
    }
    catch(Exception e)
    {
      e.printStackTrace();
     conn.rollback();
    }
    }

  //对数据库进行更新操作
  public void updateRecord() throws SQLException,UnsupportedEncodingException
  {
    try
    {
      PreparedStatement update_stm=conn.prepareStatement(query_statement);
      if(param!=null)
      {
        for(int i=0;i<=param.length;i++)
        {
          update_stm.setString(i+1,param[i]);
          update_stm.executeUpdate();
          conn.close();
          conn.commit();
        }
      }
    }
    catch(Exception e)
    {
      e.printStackTrace();
      conn.rollback();
    }
  }

  //删除数据记录
  public void deleteRecord() throws SQLException,UnsupportedEncodingException
  {
    try
    {
      PreparedStatement delete_stm=conn.prepareStatement(query_statement);
      if(param!=null)
      {
        for(int i=0;i<=param.length;i++)
        {
          delete_stm.setString(i+1,param[i]);
          delete_stm.executeUpdate();
          conn.close();
          conn.commit();
        }
      }
    }
    catch(Exception e)
    {
      e.printStackTrace();
      conn.rollback();
    }
  }



}

下面是JSP代码：

<%@ page contentType="text/html; charset=gb2312" language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%@ page import="java.sql.*"%>
<%@ page import="test.QueryBean"%>
<jsp:useBean id="query" class="test.QueryBean" scope="page">
</jsp:useBean>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>My JSP 'queryjavaBeanjap.jsp' starting page</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>

<body>
<%//查询数据库
ResultSet rs=null;
String sqlString="select * from userTable";
try
{
query.setConnection("sun.jdbc.odbc.JdbcOdbcDriver","jdbc:odbc:testDB");

//设置SQL语句
query.setQueryStatemnet(sqlString);
rs=query.getResult();

}
catch(Exception e)
{
System.out.print("SQL异常！");
}

%>
<%//显示数据
out.print("<table border=1 width=700 align=center bgcolor=#33FFFF>");
out.print("<tr>");
out.print("<td colspan=7 align=center>用QueryBean查询得到的用户数据</td></tr>");
out.print("<tr>");
out.print("<td>"+"用户ID");
out.print("<td>"+"用户名");
out.print("<td>"+"用户真实姓名");
out.print("<td>"+"年龄");
out.print("<td>"+"性别");
out.print("<td>"+"联系地址");
out.print("<td>"+"联系电话");
out.print("</tr>");
rs.beforeFirst();
while(rs.next())
{
out.print("<tr>");
out.print("<td>"+rs.getLong("ID")+"</td>");
out.print("<td>"+rs.getString("username")+"</td>");
out.print("<td>"+rs.getString("truename")+"</td>");
out.print("<td>"+rs.getInt("age")+"</td>");
out.print("<td>"+rs.getString("sex")+"</td>");
out.print("<td>"+rs.getString("address")+"</td>");
out.print("<td>"+rs.getString("tel")+"</td>");
out.print("</tr>");

}
out.print("</table>");

%>
</body>
</html>

下面是错误提示：
type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException
  org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:510)
  org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
  org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
  org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
  javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

root cause

java.lang.NullPointerException
  org.apache.jsp.queryjavaBeanjsp_jsp._jspService(org.apache.jsp.queryjavaBeanjsp_jsp:121)
  org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
  javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
  org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
  org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
  org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
  javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

note The full stack trace of the root cause is available in the Apache Tomcat/5.5.15 logs.

非常感谢各位能帮我解决这个问题~~谢谢！！

2.Re:一个JavaBean的问题，大家进来看一下！ [Re: zrwl]	Copy to clipboard
Posted by: xiaoqiang Posted on: 2006-03-24 22:50 rs=query.getResult(); 没有正确的返回值

3.Re:一个JavaBean的问题，大家进来看一下！ [Re: zrwl]	Copy to clipboard
Posted by: chunming_buaa Posted on: 2006-03-26 11:04 //设置SQL查询语句 public void setQueryStatemnet(String query_statement) { this.query_statement=query_statement; } 这里Statemnet 拼正确了？！！

4.Re:一个JavaBean的问题，大家进来看一下！ [Re: chunming_buaa]	Copy to clipboard
Posted by: zrwl Posted on: 2006-03-26 20:29 多谢~~虽然这里写成了setQueryStatemnet，但是在JSP页面跟JAVABEAN中是一致的，不受影响。