connectionpool.java

Describes basic connections from java to database.

package com.jsc.database;

import java.util.*;
import java.sql.*;

public class ConnectionPool {

    private String m_driver = new String("");
    private String m_url = new String("");
    private int m_size = 0;
    private String m_username = new String("");
    private String m_password = new String("");
    private Vector m_pool = null;

    public ConnectionPool() {
    }

    public void setDriver(String value) {
        if (value != null) {
            m_driver = value;
        }
    }

    public String getDriver() {
        return m_driver;
    }

    public void setURL(String value) {
        if (value != null) {
            m_url = value;
        }
    }

    public String getURL() {
        return m_url;
    }

    public void setSize(int value) {
        if (value > 1) {
            m_size = value;
        }
    }

    public int getSize() {
        return m_size;
    }

    public void setUsername(String value) {
        if (value != null) {
            m_username = value;
        }
    }

    public String getUserName() {
        return m_username;
    }

    public void setPassword(String value) {
        if (value != null) {
            m_password = value;
        }
    }

    public String getPassword() {
        return m_password;
    }

    private Connection createConnection() throws Exception {
        Connection _conn = null;
        _conn = DriverManager.getConnection(m_url, m_username, m_password);
        return _conn;
    }

    public synchronized void initializePool() throws Exception {
        if (m_driver == null) {
            throw new Exception("No Driver Name Specified!");
        }
        if (m_url == null) {
            throw new Exception("No URL Specified!");
        }
        if (m_size < 1) {
            throw new Exception("Pool size is less than 1!");
        }

        try {
            Class.forName(m_driver);
            for (int x=0;x<m_size;x++) {
                System.err.println("# Opening JDBC Connection " + x);
                Connection _conn = createConnection();
                if ( _conn != null ) {
                    PooledConnection pc = new PooledConnection(_conn);
                    addConnection(pc);
                }
            }
        } catch (SQLException e) {
            System.err.println(e.getMessage());
        } catch (ClassNotFoundException e) {
            System.err.println(e.getMessage());
        } catch (Exception e) {
            System.err.println(e.getMessage());
        }
    }

    private void addConnection(PooledConnection value) {
        if (m_pool == null) {
            m_pool = new Vector(m_size);
        }
        m_pool.addElement(value);
    }

    public synchronized void releaseConnection(Connection conn) {
        for (int x=0;x<m_pool.size();x++) {
            PooledConnection pc = (PooledConnection)m_pool.elementAt(x);
            if (pc.getConnection() == conn ) {
                System.err.println("Releasing Connection " + x);
                pc.setInUse(false);
                break;
            }
        }
    }

    public synchronized Connection getConnection() throws Exception {
        PooledConnection pc = null;
        for (int x=0;x<m_pool.size();x++) {
            pc = (PooledConnection)m_pool.elementAt(x);
            if (pc.inUse() == false) {
                pc.setInUse(true);
                return pc.getConnection();
            }
        }

        try {
            Connection _conn = createConnection();
            pc = new PooledConnection(_conn);
            pc.setInUse(true);
            m_pool.addElement(pc);
        } catch (Exception e) {
            System.err.println(e.getMessage());
        }
        return pc.getConnection();
    }

    public synchronized void emptyPool() {
        for (int x=0;x<m_pool.size();x++) {
            System.err.println("Closing JDBC Connection " + x);
            PooledConnection pc = (PooledConnection)m_pool.elementAt(x);
            if (pc.inUse() == false) {
                pc.close();
            } else {
                try {
                    java.lang.Thread.sleep(30000);
                    pc.close();
                } catch (InterruptedException e) {
                    System.err.println(e.getMessage());
                }
            }
        }
    }
}