dbconnectionpool.java

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package com.hxyh.sanny.mms.telecom.tool;
import java.sql.*;
import java.lang.reflect.*;
import java.util.*;
import java.io.*;

public class DBConnectionPool {
  private static LinkedList m_notUsedConnection = new LinkedList();
  private static HashSet m_usedUsedConnection = new HashSet();
  private static String m_url = "";
  private static String m_user = "";
  private static String m_password = "";
  static final boolean DEBUG = true;
  static private long m_lastClearClosedConnection = System.currentTimeMillis();
//  public static long CHECK_CLOSED_CONNECTION_TIME = 4 * 60 * 60 * 1000; //4 hours
  public static long CHECK_CLOSED_CONNECTION_TIME = 1; //4 hours

  private DBConnectionPool() {
  }

  public static void initDriver(String sdrvName) {
    Driver driver = null;
//load mysql driver
    try {
      driver = (Driver) Class.forName(sdrvName).newInstance();
      installDriver(driver);
    }
    catch (Exception e) {
    }

//load postgresql driver
    try {
      driver = (Driver) Class.forName("org.postgresql.Driver").newInstance();
      installDriver(driver);
    }
    catch (Exception e) {
    }
  }

  public static void installDriver(Driver driver) {
    try {
      DriverManager.registerDriver(driver);
    }
    catch (Exception e) {
      e.printStackTrace(System.out);
    }
  }

  public static synchronized Connection getConnection() {
    clearClosedConnection();
    while (m_notUsedConnection.size() > 0) {
      try {
        ConnectionWrapper wrapper = (ConnectionWrapper) m_notUsedConnection.
            removeFirst();
        if (wrapper.connection.isClosed()) {
          continue;
        }
        m_usedUsedConnection.add(wrapper);
        if (DEBUG) {
          wrapper.debugInfo = new Throwable("Connection initial statement");
        }
        return wrapper.connection;
      }
      catch (Exception e) {
      }
    }
    int newCount = getIncreasingConnectionCount();
    LinkedList list = new LinkedList();
    ConnectionWrapper wrapper = null;
    for (int i = 0; i < newCount; i++) {
      wrapper = getNewConnection();
      if (wrapper != null) {
        list.add(wrapper);
      }
    }
    if (list.size() == 0) {
      return null;
    }
    wrapper = (ConnectionWrapper) list.removeFirst();
    m_usedUsedConnection.add(wrapper);

    m_notUsedConnection.addAll(list);
    list.clear();

    return wrapper.connection;
  }
private static int m_nCount=0;
  private static ConnectionWrapper getNewConnection() {
    try {
      Connection con = DriverManager.getConnection(m_url, m_user, m_password);
      ConnectionWrapper wrapper = new ConnectionWrapper(con);
      return wrapper;
    }
    catch (Exception e) {
      e.printStackTrace(System.out);
    }
    return null;
  }

  static synchronized void pushConnectionBackToPool(ConnectionWrapper con) {
    boolean exist = m_usedUsedConnection.remove(con);
    if (exist) {
      m_notUsedConnection.addLast(con);
    }
  }

  public static synchronized int close() {
    int count = 0;

    Iterator iterator = m_notUsedConnection.iterator();
    while (iterator.hasNext()) {
      try {
        ( (ConnectionWrapper) iterator.next()).close();
        count++;
      }
      catch (Exception e) {
      }
    }
    m_notUsedConnection.clear();

    iterator = m_usedUsedConnection.iterator();
    while (iterator.hasNext()) {
      try {
        ConnectionWrapper wrapper = (ConnectionWrapper) iterator.next();
        wrapper.close();
        if (DEBUG) {
          wrapper.debugInfo.printStackTrace();
        }
        count++;
      }
      catch (Exception e) {
      }
    }
    m_usedUsedConnection.clear();

    return count;
  }

  private static void clearClosedConnection() {
    long time = System.currentTimeMillis();
//sometimes user change system time,just return
    if (time < m_lastClearClosedConnection) {
      time = m_lastClearClosedConnection;
      return;
    }
//no need check very often
    if (time - m_lastClearClosedConnection < CHECK_CLOSED_CONNECTION_TIME) {
      return;
    }
    m_lastClearClosedConnection = time;

//begin check
    Iterator iterator = m_notUsedConnection.iterator();
    while (iterator.hasNext()) {
      ConnectionWrapper wrapper = (ConnectionWrapper) iterator.next();
      try {
        if (wrapper.connection.isClosed()) {
          iterator.remove();
        }
      }
      catch (Exception e) {
        iterator.remove();
        if (DEBUG) {
          System.out.println(
              "connection is closed, this connection initial StackTrace");
          wrapper.debugInfo.printStackTrace();
        }
      }
    }

//make connection pool size smaller if too big
    int decrease = getDecreasingConnectionCount();
    if (m_notUsedConnection.size() < decrease) {
      return;
    }

    while (decrease-- > 0) {
      ConnectionWrapper wrapper = (ConnectionWrapper) m_notUsedConnection.
          removeFirst();
      try {
        wrapper.connection.close();
      }
      catch (Exception e) {
      }
    }
  }

  /**
   * get increasing connection count, not just add 1 connection
   * @return count
   */
  public static int getIncreasingConnectionCount() {
    int count = 1;
    int current = getConnectionCount();
    count = current / 4;
    if (count < 1) {
      count = 1;
    }
    return count;
  }

  /**
   * get decreasing connection count, not just remove 1 connection
   * @return count
   */
  public static int getDecreasingConnectionCount() {
    int count = 0;
    int current = getConnectionCount();
    if (current < 10) {
      return 0;
    }
    return current / 3;
  }

  public synchronized static void printDebugMsg() {
    printDebugMsg(System.out);
  }

  public synchronized static void printDebugMsg(PrintStream out) {
    if (DEBUG == false) {
      return;
    }
    StringBuffer msg = new StringBuffer();
    msg.append("debug message in " + DBConnectionPool.class.getName());
    msg.append("\r\n");
    msg.append("total count is connection pool: " + getConnectionCount());
    msg.append("\r\n");
    msg.append("not used connection count: " + getNotUsedConnectionCount());
    msg.append("\r\n");
    msg.append("used connection, count: " + getUsedConnectionCount());
    out.println(msg);
    Iterator iterator = m_usedUsedConnection.iterator();
    while (iterator.hasNext()) {
      ConnectionWrapper wrapper = (ConnectionWrapper) iterator.next();
      wrapper.debugInfo.printStackTrace(out);
    }
    out.println();
  }

  public static synchronized int getNotUsedConnectionCount() {
    return m_notUsedConnection.size();
  }

  public static synchronized int getUsedConnectionCount() {
    return m_usedUsedConnection.size();
  }

  public static synchronized int getConnectionCount() {
    return m_notUsedConnection.size() + m_usedUsedConnection.size();
  }

  public static String getUrl() {
    return m_url;
  }

  public static void setUrl(String url) {
    if (url == null) {
      return;
    }
    m_url = url.trim();
  }

  public static String getUser() {
    return m_user;
  }

  public static void setUser(String user) {
    if (user == null) {
      return;
    }
    m_user = user.trim();
  }

  public static String getPassword() {
    return m_password;
  }

  public static void setPassword(String password) {
    if (password == null) {
      return;
    }
    m_password = password.trim();
  }

}

class ConnectionWrapper
    implements InvocationHandler {
  private final static String CLOSE_METHOD_NAME = "close";
  public Connection connection = null;
  private Connection m_originConnection = null;
  public long lastAccessTime = System.currentTimeMillis();
  Throwable debugInfo = new Throwable("Connection initial statement");

  ConnectionWrapper(Connection con) {
    Class[] interfaces = {
        java.sql.Connection.class};
    this.connection = (Connection) Proxy.newProxyInstance(
        con.getClass().getClassLoader(),
        interfaces, this);
    m_originConnection = con;
  }

  void close() throws SQLException {
    m_originConnection.close();
  }

  public Object invoke(Object proxy, Method m, Object[] args) throws Throwable {
    Object obj = null;
    if (CLOSE_METHOD_NAME.equals(m.getName())) {
      DBConnectionPool.pushConnectionBackToPool(this);
    }
    else {
      obj = m.invoke(m_originConnection, args);
    }
    lastAccessTime = System.currentTimeMillis();
    return obj;
  }
}