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why jsp cannot use this class, which is no problem when compile singlely.

 
Sean Li
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I use a declaration in a jsp file:
<%! DBConnectionManager dd; %>
the compiler tell me that the class below contain problems. while i found no problem when i compile the class. what's wrong? is there any convention when declare a class within a jsp file? please help me!
package callcenter;
import java.io.*;
import java.sql.*;
import java.util.*;
import java.util.Date;
public class DBConnectionManager {
static private DBConnectionManager instance; // The single instance
private Vector drivers = new Vector();
private PrintWriter log;
private Hashtable pools = new Hashtable();
private Hashtable clients = new Hashtable();
/**
* A private constructor since this is a Singleton
*/
private DBConnectionManager()
throws SQLException {
init();
}
/**
* Loads properties and initializes the instance with its values.
*/
private void init() throws SQLException {
log = new PrintWriter(System.err);
loadDrivers();
//createPools(0);
}
/**
* Loads and registers all JDBC drivers. This is done by the
* DBConnectionManager, as opposed to the DBConnectionPool,
* since many pools may share the same driver.
*
* @param props The connection pool properties
*/
private void loadDrivers() throws SQLException {
DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
}
/**
* Returns the single instance, creating one if it's the
* first time this method is called.
*
* @return DBConnectionManager The single instance.
*/
public static synchronized DBConnectionManager getInstance()
throws SQLException
{
if (instance == null) {
instance = new DBConnectionManager();
}
return instance;
}
/**
* Returns an open connection. If no one is available, and the max
* number of connections has not been reached, a new connection is
* created.
* @param name The pool name as defined in the properties file
* @return Connection The connection or null
*/
public Connection getConnection(String name,String url,String username,String password) throws SQLException {
if (!clients.containsKey(name)) {
createPool(name,url,username,password,0);
clients.put(name,new Integer(0));
}
int iCurr = ((Integer)clients.get(name)).intValue();
iCurr++;
clients.put(name,new Integer(iCurr));
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null) {
return pool.getConnection();
}
return null;
}
private void createPool(String poolName,String url,String username,String password,int max) {
DBConnectionPool pool = new DBConnectionPool(poolName,url,username,password, max);
pools.put(poolName, pool);
log("Initialized pool " + poolName);
}

/**
* Returns a connection to the named pool.
* @param name The pool name as defined in the properties file
* @param con The Connection
*/
public void freeConnection(String name, Connection con) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null) {
pool.freeConnection(con);
}
}
/**
* Closes all open connections and deregisters all drivers.
*/
public synchronized void release(String name) throws SQLException {
// Wait until called by the last client
if (!clients.containsKey(name)) return;
int iCurr = ((Integer)clients.get(name)).intValue();
iCurr--;
clients.put(name,new Integer(iCurr));
if (iCurr > 0) return;
clients.remove(name);
DBConnectionPool pool = (DBConnectionPool)pools.get(name);
pool.release();
if (!pools.isEmpty()) return;
Enumeration allDrivers = drivers.elements();
while (allDrivers.hasMoreElements()) {
Driver driver = (Driver) allDrivers.nextElement();
DriverManager.deregisterDriver(driver);
}
}
/**
* Writes a message to the log file.
*/
private void log(String msg) {
log.println(new Date() + ": " + msg);
}
/**
* Writes a message with an Exception to the log file.
*/
private void log(Throwable e, String msg) {
log.println(new Date() + ": " + msg);
e.printStackTrace(log);
}
/**
* This inner class represents a connection pool. It creates new
* connections on demand, up to a max number if specified.
* It also makes sure a connection is still open before it is
* returned to a client.
*/
class DBConnectionPool {
private int checkedOut;
private Vector freeConnections = new Vector();
private int maxConn;
private String name;
private String password;
private String URL;
private String user;
/**
* Creates new connection pool.
*
* @param name The pool name
* @param URL The JDBC URL for the database
* @param user The database user, or null
* @param password The database user password, or null
* @param maxConn The maximal number of connections, or 0
* for no limit
*/
public DBConnectionPool(String name, String URL, String user,String password,int maxConn) {
this.name = name;
this.URL = URL;
this.user = user;
this.password = password;
this.maxConn = maxConn;
}
/**
* Checks in a connection to the pool. Notify other Threads that
* may be waiting for a connection.
*
* @param con The connection to check in
*/
public synchronized void freeConnection(Connection con) {
// Put the connection at the end of the Vector
freeConnections.addElement(con);
checkedOut--;
notifyAll();
}
/**
* Checks out a connection from the pool. If no free connection
* is available, a new connection is created unless the max
* number of connections has been reached. If a free connection
* has been closed by the database, it's removed from the pool
* and this method is called again recursively.
*/
public synchronized Connection getConnection() throws SQLException {
Connection con = null;
if (freeConnections.size() > 0) {
// Pick the first Connection in the Vector
// to get round-robin usage
con = (Connection) freeConnections.firstElement();
freeConnections.removeElementAt(0);
if (con.isClosed()) {
log("Removed bad connection from " + name);
// Try again recursively
con = getConnection();
}
}
else if (maxConn == 0 || checkedOut < maxConn) {
con = newConnection();
}
if (con != null) {
checkedOut++;
}
return con;
}
/**
* Closes all available connections.
*/
public synchronized void release() throws SQLException {
Enumeration allConnections = freeConnections.elements();
while (allConnections.hasMoreElements()) {
Connection con = (Connection) allConnections.nextElement();
con.close();
}
freeConnections.removeAllElements();
}
/**
* Creates a new connection, using a userid and password
* if specified.
*/
private Connection newConnection() throws SQLException {
Connection con = null;
if (user == null) {
con = DriverManager.getConnection(URL);
}
else {
con = DriverManager.getConnection(URL, user, password);
}
log("Created a new connection in pool " + name);
return con;
}
}
}
[ May 07, 2002: Message edited by: Sean Lee ]
 
mustang india
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It would be more helpful if u can show the JSP code. U say that the Class is compiling properly, then there is no problem with this code.
Did u import the package callcenter in ur JSP ?
Regards,
Mustang.
 
Sean Li
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Posts: 154
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thanks for your reply, my jsp code is very simple:
<%@ page contentType="text/html; charset=GBK" %>
<%@ page import="CallCenter.*" %>
<html>
<head>
<title>
test
</title>
</head>
<body>
<h1>
JBuilder Generated JSP
</h1>
<%! DBConnectionManager dd;%>
</body>
</html>
the errormessage is: "test.jsp": Error #: 302 : cannot access class DBConnectionManager; class file: CallCenter.DBConnectionManager contains wrong class: callcenter.DBConnectionManager at line 13
the compiler i'm using is jbuilder6.
 
Sean Li
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i think the difference is that the class contain a subclass. isn't it? anybody help me?
 
Jessica Sant
Sheriff
Posts: 4313
Android IntelliJ IDE Java
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Originally posted by Sean Lee:
the errormessage is: "test.jsp": Error #: 302 : cannot access class DBConnectionManager; class file: CallCenter.DBConnectionManager contains wrong class: callcenter.DBConnectionManager at line 13

Always remember -- Java is CaSe SeNsItIvE.
In your DBConnectionManager class you defined the package as: "package callcenter;"
But in the JSP you're importing: "<%@ page import="CallCenter.*" %>
Pick one -- then try running it again.
Hope that helps!
[ May 08, 2002: Message edited by: Jessica Sant ]
 
Sean Li
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Posts: 154
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oh, my god, thank u, buddy. thanks for your patient. u r really helpful.
 
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