求助！！请高手指点！（有时提示“无效的游标错误！”）
/*
*下边是jsp页面文件
*/
<%@ page contentType= "text/html; charset=gb2312 " language= "java " import= "java.sql.*,bean.DBClass " errorPage= " " %>
<table width= "75% " align= "right " border= "0 ">
<%
String query= "SELECT * FORM message ";
String userId= " ";
String message= " ";
String date= " ";
DBClass db=new DBClass();
db.connect();
ResultSet rt=db.executeQuery(query);
while(rt.next()){
userId=rt.getString( "userId ");
message=rt.getString( "message ");
date=rt.getString( "date ");
%>
<tr> <td>
留言者: <%=userId %> <%=date %> </td> </tr>
<tr> <%=message %> </tr>
<%
}
db.closeConnection();
%>
<tr> <td>
<form name= "form3 " method= "post " action= "/MsgBoard/UserComment ">
<div align= "center "> 我要发言:(不超过50字) <font color= "#FF0000 " size= "-1 "> <% if (request.getAttribute( "errInf2 ")!=null){ %>
<%=(String)request.getAttribute( "errInf2 ") %> <% } %> </font>
<p align= "center ">
<textarea name= "comment " cols= "30 " rows= "9 " > </textarea> </p>
<p align= "center ">
<input name= "submit " type= "submit " value= "发布 "/>
<input name= "reset " type= "reset " value= "重写 "/> </p>
</div>
</form> </td> </tr>
</table>
/* DBClass 原代码，编译过 没有错误
* Designed by *****
*/
package bean;
import java.io.*;
import java.util.*;
import java.sql.*;
public class DBClass
{
private String driver;
private String url;
private String username;
private String password;
private Connection connection;
private Statement statement;
private String message= " ";
public DBClass(){
driver= "sun.jdbc.odbc.JdbcOdbcDriver ";
url= "jdbc:odbc:msgboard ";
username= " ";
password= " ";
connection=null;
statement=null;
message= " ";
}
public DBClass(String driver,String url,String username,String password){
this.driver=driver;
this.url=url;
this.username=username;
this.password=password;
this.connection=null;
this.statement=null;
this.message= " ";
}
public String getDriver(){
return driver;
}
public void setDriver(String driver){
this.driver=driver;
}
public String getUrl(){
return url;
}
public void setUrl(String url){
this.url=url;
}
public String getUsername(){
return username;
}
public void setUsername(String username){
this.username=username;
}
public String getPassword(){
return password;
}
public void setPassword(String password){
this.password=password;
}
public Connection getConnection(){
return connection;
}
public void setConnection(Connection connection){
this.connection=connection;
}
public Statement getStatement(){
return statement;
}
public void setStatement(Statement statement){
this.statement=statement;
}
public String getMessage(){
return message;
}
public void setMessage(String message){
this.message=message;
}
/*link to database*/
public void connect(){
try{
Class.forName(driver);
connection=DriverManager.getConnection(url,username,password);
statement=connection.createStatement();
}catch(ClassNotFoundException cnfe){
message= "connection: "+cnfe;
}catch(SQLException sqle){
message= "executeQuery: "+sqle;
}
}
/*Seclet and return result*/
public ResultSet executeQuery(String query){
ResultSet resultset=null;
try{
resultset=statement.executeQuery(query);
}catch(SQLException sqle){
message= "executeQuery: "+sqle;
}
return resultset;
}
/*Update the database*/
public void executeUpdate(String command){
try{
statement.executeUpdate(command);
}catch(SQLException sqle){
message= "executeUpdate: "+sqle;
}
}
/*close the database*/
public void closeConnection(){
try{
connection.close();
}catch(SQLException sqle){
message= "closeConnection: "+sqle;
}
}
}
/*
*jsp页面调试错误，调试环境tomcat6.0+jdk1.5 , Dreamweaver8.0
*/
HTTP Status 500 -
--------------------------------------------
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException: An exception occurred processing JSP page /utility/comment.jsp at line 11
8: DBClass db=new DBClass();
9: db.connect();
10: ResultSet rt=db.executeQuery(query);
11: while(rt.next()){
12: userId=rt.getString( "userId ");
13: message=rt.getString( "message ");
14: date=rt.getString( "date ");
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:515)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:426)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
root cause
java.lang.NullPointerException
org.apache.jsp.utility.comment_jsp._jspService(comment_jsp.java:65)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:384)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.10 logs.
--------------------------------------------
Apache Tomcat/6.0.10
[解决办法]
db.connect(); 这个方法不应该是返回void 而应该返回一个Statement类型的
[解决办法]
第一，你先看看你的connection是否为null;第二，你要看看你的statement是否为null
我的异常网推荐解决方案：An exception occurred processing JSP page,http://www.myexception.cn/j2se/33144.html
我的异常网推荐解决方案：The server encountered an internal error () that prevented it from fulfilling this request.,http://www.myexception.cn/java-web/317.html
