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So I'm starting with an application I have to make for a certain class in college and I already stumble onto a large problem at the start of my project. I'm planning on getting it to work in JBuilder, even though I hate that program. I made a database in JDatastore and I'm trying to connect to it by using a connection pool I made. (more like "jacked from the book")
This is the driver I'm trying to use and also the name of the database:
Which will be implemented in:
And..
This is EXACTLY how the book does it, yet it doesn't work for me. They used a database created in Access though (.mdb), but mine was made in JDataStore(.jds).
I test the connection pool in a JSP files I made and I run it on a Tomcat 4.0 server, which isn't the latest version, but this is the exact output I'm getting:
If anyone could help me with whatever I'm doing wrong, I would be very grateful.
I'll also append all my code to this post:
PooledConnection.java (the problem isn't here)
ConnectionPool.java (the problem shouldn't be here either)
Catalog.jsp (I believe the problem is in here
)
This is the driver I'm trying to use and also the name of the database:
Code:
pool.setDriver("sun.jdbc.odbc.JdbcOdbcDriver");
pool.setURL("MuseumDatabase.jds");Which will be implemented in:
Code:
Class.forName(driver);And..
Code:
con = DriverManager.getConnection(url,
username, password);This is EXACTLY how the book does it, yet it doesn't work for me. They used a database created in Access though (.mdb), but mine was made in JDataStore(.jds).
I test the connection pool in a JSP files I made and I run it on a Tomcat 4.0 server, which isn't the latest version, but this is the exact output I'm getting:
If anyone could help me with whatever I'm doing wrong, I would be very grateful.
I'll also append all my code to this post:
PooledConnection.java (the problem isn't here)
Code:
package asa_prototype;
import java.sql.*;
import java.io.*;
public class PooledConnection implements Serializable{
// Real JDBC Connection
private Connection connection = null;
// boolean flag used to determine if connection is in use
private boolean inuse = false;
// Constructor that takes the passed in JDBC Connection
// and stores it in the connection attribute.
public PooledConnection(Connection value) {
if ( value != null ) {
connection = value;
}
}
// Returns a reference to the JDBC Connection
public Connection getConnection() {
// get the JDBC Connection
return connection;
}
// Set the status of the PooledConnection.
public void setInUse(boolean value) {
inuse = value;
}
// Returns the current status of the PooledConnection.
public boolean inUse() {
return inuse;
}
// Close the real JDBC Connection
public void close() {
try {
connection.close();
}
catch (SQLException sqle) {
System.err.println(sqle.getMessage());
}
}
}ConnectionPool.java (the problem shouldn't be here either)
Code:
package asa_prototype;
import java.io.*;
import java.sql.*;
import java.util.*;
public class ConnectionPool implements Serializable{
// JDBC Driver Name
private String driver = null;
// URL of database
private String url = null;
// Initial number of connections.
private int size = 0;
// Username
private String username = new String("");
// Password
private String password = new String("");
// Vector of JDBC Connections
private Vector pool = null;
public ConnectionPool() {
}
// Set the value of the JDBC Driver
public void setDriver(String value) {
if ( value != null ) {
driver = value;
}
}
// Get the value of the JDBC Driver
public String getDriver() {
return driver;
}
// Set the URL Pointing to the Datasource
public void setURL(String value ) {
if ( value != null ) {
url = value;
}
}
// Get the URL Pointing to the Datasource
public String getURL() {
return url;
}
// Set the initial number of connections
public void setSize(int value) {
if ( value > 1 ) {
size = value;
}
}
// Get the initial number of connections
public int getSize() {
return size;
}
// Set the username
public void setUsername(String value) {
if ( value != null ) {
username = value;
}
}
// Get the username
public String getUserName() {
return username;
}
// Set the password
public void setPassword(String value) {
if ( value != null ) {
password = value;
}
}
// Get the password
public String getPassword() {
return password;
}
// Creates and returns a connection
private Connection createConnection() throws Exception {
Connection con = null;
// Create a Connection
con = DriverManager.getConnection(url,
username, password);
return con;
}
// Initialize the pool
public synchronized void initializePool() throws Exception {
// Check our initial values
if ( driver == null ) {
throw new Exception("No Driver Name Specified!");
}
if ( url == null ) {
throw new Exception("No URL Specified!");
}
if ( size < 1 ) {
throw new Exception("Pool size is less than 1!");
}
// Create the Connections
try {
// Load the Driver class file
Class.forName(driver);
// Create Connections based on the size member
for ( int x = 0; x < size; x++ ) {
Connection con = createConnection();
if ( con != null ) {
// Create a PooledConnection to encapsulate the
// real JDBC Connection
PooledConnection pcon = new PooledConnection(con);
// Add the Connection to the pool.
addConnection(pcon);
}
}
}
catch (Exception e) {
System.err.println(e.getMessage());
throw new Exception(e.getMessage());
}
}
// Adds the PooledConnection to the pool
private void addConnection(PooledConnection value) {
// If the pool is null, create a new vector
// with the initial size of "size"
if ( pool == null ) {
pool = new Vector(size);
}
// Add the PooledConnection Object to the vector
pool.addElement(value);
}
public synchronized void releaseConnection(Connection con) {
// find the PooledConnection Object
for ( int x = 0; x < pool.size(); x++ ) {
PooledConnection pcon =
(PooledConnection)pool.elementAt(x);
// Check for correct Connection
if ( pcon.getConnection() == con ) {
System.err.println("Releasing Connection " + x);
// Set its inuse attribute to false, which
// releases it for use
pcon.setInUse(false);
break;
}
}
}
// Find an available connection
public synchronized Connection getConnection()
throws Exception {
PooledConnection pcon = null;
// find a connection not in use
for ( int x = 0; x < pool.size(); x++ ) {
pcon = (PooledConnection)pool.elementAt(x);
// Check to see if the Connection is in use
if ( pcon.inUse() == false ) {
// Mark it as in use
pcon.setInUse(true);
// return the JDBC Connection stored in the
// PooledConnection object
return pcon.getConnection();
}
}
// Could not find a free connection,
// create and add a new one
try {
// Create a new JDBC Connection
Connection con = createConnection();
// Create a new PooledConnection, passing it the JDBC
// Connection
pcon = new PooledConnection(con);
// Mark the connection as in use
pcon.setInUse(true);
// Add the new PooledConnection object to the pool
pool.addElement(pcon);
}
catch (Exception e) {
System.err.println(e.getMessage());
throw new Exception(e.getMessage());
}
// return the new Connection
return pcon.getConnection();
}
// When shutting down the pool, you need to first empty it.
public synchronized void emptyPool() {
// Iterate over the entire pool closing the
// JDBC Connections.
for ( int x = 0; x < pool.size(); x++ ) {
System.err.println("Closing JDBC Connection " + x);
PooledConnection pcon =
(PooledConnection)pool.elementAt(x);
// If the PooledConnection is not in use, close it
if ( pcon.inUse() == false ) {
pcon.close();
}
else {
// If it is still in use, sleep for 30 seconds and
// force close.
try {
java.lang.Thread.sleep(30000);
pcon.close();
}
catch (InterruptedException ie) {
System.err.println(ie.getMessage());
}
}
}
}
}Catalog.jsp (I believe the problem is in here
)
Code:
<html>
<head>
<title>
Catalog
</title>
</head>
<body>
<%@ page import= "java.io.*" %>
<%@ page import= "java.util.*" %>
<%@ page import= "java.sql.*" %>
<!-- Instatiate the ConnectionPool bean with id of "pool" -->
<jsp:useBean id="pool"
scope="application"
class="asa_prototype.ConnectionPool"
/>
<%
Connection con = null;
try{
if(pool.getDriver() == null){
//Initialize pool
pool.setDriver("sun.jdbc.odbc.JdbcOdbcDriver");
pool.setURL("MuseumDatabase.jds");
pool.setSize(5);
pool.setUsername("wjvs");
pool.setPassword("boink");
pool.initializePool();
}
//Get a connection from the ConnectionPool
con = pool.getConnection();
//Create the statement
Statement statement = con.createStatement();
//SQL query SELECTs DATA
//FROM the Artifacts Table
ResultSet rs = statement.executeQuery("SELECT * " + "FROM ARTIFACTS");
//Iterate over results
%>
<!-- Add a n HTML table to format the results -->
<center>
<table border="1" cellspacing="0" cellpadding="2" width="500">
<tr>
<th>BLA</th></tr>
<%
while (rs.next()){
//print names
out.println("<tr>\n<td>" + rs.getString("NAME") + "</td>\n</tr>");
}
//Close the Resultset
rs.close();
out.println("</table></center>");
}
catch (IOException ioe){
out.println(ioe.getMessage());
}
catch (SQLException sqle){
out.println(sqle.getMessage());
}
catch (ClassNotFoundException cnfe){
out.println(cnfe.getMessage());
}
catch (Exception e){
out.println(e.getMessage());
}
finally{
try{
if(con != null){
//release the connection
pool.releaseConnection(con);
}
}
catch(Exception e){
out.println(e.getMessage());
}
}
%>
</table>
</center>
</body>
</html>
