js| Connection Database | Problem You can help me look at the following three files (a JSP, two. java), I entered the address in IE, prompted the following error (code should not be wrong, do not know if the problem is set up), look at the high finger teach, appreciate:
D:\Program Files\apache group\tomcat 4.1\work\standalone\localhost\_\shopping\index_jsp.java:44:package Mybean does Not exist
Mybean. Dbconnmanager Connmanager = null;
^
An error occurred at Line:2 in the JSP file:/shopping/index.jsp
Generated servlet error:
D:\Program Files\apache group\tomcat 4.1\work\standalone\localhost\_\shopping\index_jsp.java:46:package Mybean does Not exist
Connmanager = (Mybean. Dbconnmanager) Pagecontext.getattribute ("Connmanager", Pagecontext.application_scope);
^
An error occurred at Line:2 in the JSP file:/shopping/index.jsp
Generated servlet error:
D:\Program Files\apache group\tomcat 4.1\work\standalone\localhost\_\shopping\index_jsp.java:49:package Mybean does Not exist
Connmanager = (Mybean. Dbconnmanager) Java.beans.Beans.instantiate (This.getclass (). getClassLoader (), Mybean. Dbconnmanager ");
^
The following two are connection pools, the following two files are placed in a mybean bag.
Package Mybean;
Import java.sql.*;
Import java.util.*;
public class Dbconnpool {
Number of connections being used
private int using;
Current number of connections available, that is, idle connections
Private vector connections=new vector ();
Maximum number of connections
private int maxconn;
Connection Pool Name
Private String poolname;
Database identification
Private String dbid;
Driver name
Private String drivername;
Database account number
Private String username;
Database Password
Private String passwd;
Public Dbconnpool (String poolname,string dbid,string drivername,
String username,string passwd,int maxconn) {
This.poolname=poolname;
This.drivername=drivername;
This.dbid =dbid;
This.username =username;
THIS.PASSWD=PASSWD;
This.maxconn=maxconn;
}
/* Return the idle connection to the connection pool.
Public synchronized void ReturnConnection (Connection conn) {
Adds the specified connection to the end of the vector
Connections.addelement (conn);
Connect user minus One
using--;
}
/* Get a connection from the connection pool * *
Public synchronized Connection getconnection () {
Connection conn = null; Connection is a class,
Connections is a vector that stores the connection objects that are available for all idle states
if (connections.size () > 0) {
Get the first connection to a list of connections
conn = (Connection) connections.elementat (0);
Connections.removeelementat (0);//Get a connection and remove the connection from the queue.
If this connection is turned off, just continue to fetch,
try {
if (conn.isclosed ())
conn = getconnection ();
}
catch (Exception e) {
E.printstacktrace ();
}
}
If the number of connections actually used is less than the maximum number of connections available, a new connection is added
else if (maxconn = 0 | | Using < MAXCONN) {
When there is no available connection (Maxconn = 0) and the number of connections is not up to the upper limit (using < Maxconn), a new connection is created
Conn=newconnection ();
}
Returns an empty pointer if the number of connections has reached the upper limit
if (conn!=null) {
using++;
}
Return conn;
}
/* Create a new connection * *
Public Connection newconnection () {
Connection Conn=null;
try{
Load Driver
Class.forName (drivername);
Conn=drivermanager.getconnection (DBID,USERNAME,PASSWD);
}catch (Exception e) {
E.printstacktrace ();
return null;
}
Return conn;
}
/* Close all connections *
Public synchronized void Closeconn () {
Enumeration allconnections=connections.elements ();
while (Allconnections.hasmoreelements ()) {
Connection conn= (Connection) allconnections.nextelement ();
try{
Conn.close ();
}catch (SQLException e) {
E.printstacktrace ();
}
}
Connections.removeallelements ();
}
}
Package Mybean;
Import java.sql.*;
Import java.util.*;
public class Dbconnmanager {
List of connection pool names
Private vector poolnames =new vector ();
List of driver names
Private vector drivernames=new vector ();
List of database identities
Private vector dbids=new vector ();
List of user names
Private vector usernames=new vector ();
User password list
Private vector passwds=new vector ();
List of maximum connections
Private vector maxconns=new vector ();
Connection Pool Queue
Private Hashtable connpools=new Hashtable ();
Public Dbconnmanager () {
Add connection information for an Access database
Poolnames.addelement ("Access");
Drivernames.addelement ("Sun.jdbc.odbc.JdbcOdbcDriver");
Dbids.addelement ("jdbc:odbc:shopping");
Usernames.addelement ("");
Passwds.addelement ("");
Maxconns.addelement ("5");
Add connection information for SQL Server2000 database
Poolnames.addelement ("sqlserver2000");
Drivernames.addelement ("Com.microsoft.jdbc.sqlserver.SQLServerDriver");
Dbids.addelement ("jdbc:microsoft:sqlserver://localhost:1433;databsername=shopping");
Usernames.addelement ("");
Passwds.addelement ("");
Maxconns.addelement ("5");
Connecting MySQL database information
Poolnames.addelement ("MySQL");
Drivernames.addelement ("Org.gjt.mm.mysql.Driver");
Dbids.addelement ("jdbc:mysql://localhost/shopping");
Usernames.addelement ("");
Passwds.addelement ("");
Maxconns.addelement ("5");
Connecting to the Oracle8i/9i database
Poolnames.addelement ("Oracle");
Drivernames.addelement ("Oracle.jdbc.driver.OracleDriver");
Dbids.addelement ("Jdbc:oracle:thin: @localhost: 1521:shopping");
Usernames.addelement ("");
Passwds.addelement ("");
Maxconns.addelement ("5");
Create a connection pool
Createpools ();
}
/* Returns the connection to the specified connection pool.
public void ReturnConnection (String name,connection conn) {
Dbconnpool pool= (Dbconnpool) connpools.get (name);
if (pool!=null)
{
Pool.returnconnection (conn);
}
}
/* Get a connection in a specified connection pool.
Public Connection getconnection (String name) {
Dbconnpool pool= (Dbconnpool) connpools.get (name);
if (pool!=null)
{
return Pool.getconnection ();
}
return null;
}
/* Close all connections *
Public synchronized void Closeconns () {
Enumeration allpools=connpools.elements ();
while (Allpools.hasmoreelements ()) {
Dbconnpool pool= (Dbconnpool) allpools.nextelement ();
Pool.closeconn ();
}
}
/* Create Connection Pool * *
private void Createpools () {
for (int i=0;i<poolnames.size (); i++)
{
String Poolname=poolnames.elementat (i). toString ();
String Drivername=drivernames.elementat (i). toString ();
String Dbid=dbids.elementat (i). toString ();
String Username=usernames.elementat (i). toString ();
String Passwd=passwds.elementat (i). toString ();
int maxconn=0;
try{
Maxconn=integer.parseint (Maxconns.elementat (i). toString ());
}catch (NumberFormatException e) {
E.printstacktrace ();
}
Dbconnpool pool=new Dbconnpool (Poolname,drivername,dbid,username,
Passwd,maxconn);
Connpools.put (Poolname,pool);
}
}
}
Here's the main page. JSP file
<%@ page contenttype= "text/html; CHARSET=GBK "%>
<%@ page import = "java.sql.*"%>
<jsp:usebean id= "Connmanager" scope= "Application" class= "Mybean". Dbconnmanager "/>
<title>
Shopping mall Home
</title>
<body bgcolor= "#B0C4DE" >
<center><%
Connection conna=connmanager.getconnection ("Access");
Connection conns=connmanager.getconnection ("sqlserver2000");
if (conns==null)
{
%>
The database is busy, please visit again later
<%
}
Statement stmta=conna.createstatement ();
Statement stmts=conns.createstatement ();
%>
<%
String sql= "SELECT * from UserInfo";
ResultSet rs=stmts.executequery (SQL);
while (Rs.next ())
{
%>
<tr>
<td><%=rs.getstring ("username")%></td>
<td><%=rs.getstring ("Userpass")%></td>
</tr>
<%
}
Rs.close ();
Stmts.close ();
Connmanager.returnconnection ("sqlserver2000", Conns);
%>
</body>
