defaultconnectionpool.java

来自「java jdk 1.4的源码」· Java 代码 · 共 621 行 · 第 1/2 页

    //
    if ( m_pool.size() < m_PoolMinSize ) { initializePool(); }

    // find a connection not in use
    for ( int x = 0; x < m_pool.size(); x++ )
    {

      pcon = (PooledConnection) m_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

    // 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
    m_pool.addElement(pcon);

    // return the new Connection
    return pcon.getConnection();
  }

  /**
   * @param con
   * @return
   * @throws SQLException
   */
  public synchronized void releaseConnection( Connection con )throws SQLException
  {

    // find the PooledConnection Object
    for ( int x = 0; x < m_pool.size(); x++ )
    {

      PooledConnection pcon =
        (PooledConnection) m_pool.elementAt(x);

      // Check for correct Connection
      if ( pcon.getConnection() == con )
      {
        if (DEBUG)
        {
          System.out.println("Releasing Connection " + x);
        }

        if (! isEnabled())
        {
          con.close();
          m_pool.removeElementAt(x);
          if (DEBUG)
          {
            System.out.println("-->Inactive Pool, Closing connection");
          }

        }
        else
        {
          // Set it's inuse attribute to false, which
          // releases it for use
          pcon.setInUse(false);
        }

        break;
      }
    }
  }


  /**
   * @param con
   * @return
   * @throws SQLException
   */
  public synchronized void releaseConnectionOnError( Connection con )throws SQLException
  {

    // find the PooledConnection Object
    for ( int x = 0; x < m_pool.size(); x++ )
    {

      PooledConnection pcon =
        (PooledConnection) m_pool.elementAt(x);

      // Check for correct Connection
      if ( pcon.getConnection() == con )
      {
        if (DEBUG)
        {
          System.out.println("Releasing Connection On Error" + x);
        }

        con.close();
        m_pool.removeElementAt(x);
        if (DEBUG)
        {
          System.out.println("-->Inactive Pool, Closing connection");
        }
        break;
      }
    }
  }


  /**
   * @return
   * @throws SQLException
   */
  private Connection createConnection( )throws SQLException
  {
    Connection con = null;

    // Create a Connection
    con = DriverManager.getConnection( m_url, m_ConnectionProtocol );

    return con;
  }

  // Initialize the pool
  /**
   * @return
   * @throws IllegalArgumentException
   * @throws SQLException
   */
  public synchronized void initializePool( )throws IllegalArgumentException, SQLException
  {

     // Check our initial values
     if ( m_driver == null )
     {
       throw new IllegalArgumentException(XSLMessages.createMessage(XSLTErrorResources.ER_NO_DRIVER_NAME_SPECIFIED, null));
       // "No Driver Name Specified!");
     }

     if ( m_url == null )
     {
       throw new IllegalArgumentException(XSLMessages.createMessage(XSLTErrorResources.ER_NO_URL_SPECIFIED, null));
       // "No URL Specified!");
     }

     if ( m_PoolMinSize < 1 )
     {
       throw new IllegalArgumentException(XSLMessages.createMessage(XSLTErrorResources.ER_POOLSIZE_LESS_THAN_ONE, null));
       // "Pool size is less than 1!");
     }

     // Create the Connections
     // Load the Driver class file

     try
     {
        // We need to implement the context classloader
        Class cls = null;
        try 
        {
          Method m = Thread.class.getMethod("getContextClassLoader", null);
          ClassLoader classLoader = (ClassLoader) m.invoke(Thread.currentThread(), null);
          cls = classLoader.loadClass(m_driver);
        } 
        catch (Exception e) 
        {
          cls = Class.forName(m_driver);  
        }
        
        if (cls == null)
          cls = Class.forName(m_driver);

        // We have also had problems with drivers unloading
        // load an instance that will get freed with the class.
        m_Driver = cls.newInstance();


     }
     catch(ClassNotFoundException e)
     {
       throw new IllegalArgumentException(XSLMessages.createMessage(XSLTErrorResources.ER_INVALID_DRIVER_NAME, null));
       // "Invalid Driver Name Specified!");
     }
     catch(Exception e)
     {
       throw new IllegalArgumentException(XSLMessages.createMessage(XSLTErrorResources.ER_INVALID_DRIVER_NAME, null));
     }

     // IF we are not active, don't actuall build a pool yet
     // Just set up the driver and periphal items.
     if ( !m_IsActive) return;

    // Create Connections based on the size member
    do
    {

      Connection con = createConnection();

      if ( con != null )
      {

        // Create a PooledConnection to encapsulate the
        // real JDBC Connection
        PooledConnection pcon = new PooledConnection(con);

        // Add the Connection the pool.
        addConnection(pcon);

        if (DEBUG) System.out.println("Adding DB Connection to the Pool");
      }
    }
    while (m_pool.size() < m_PoolMinSize);
  }

  // Adds the PooledConnection to the pool
  /**
   * @param value
   * @return
   */
  private void addConnection( PooledConnection value )
  {
    // Add the PooledConnection Object to the vector
    m_pool.addElement(value);
  }


  /**
   * @return
   * @throws Throwable
   */
  protected void finalize( )throws Throwable
  {
    if (DEBUG)
    {
      System.out.println("In Default Connection Pool, Finalize");
    }

    // Iterate over the entire pool closing the
    // JDBC Connections.
    for ( int x = 0; x < m_pool.size(); x++ )
    {

      if (DEBUG)
      {
        System.out.println("Closing JDBC Connection " + x);
      }

      PooledConnection pcon =
        (PooledConnection) m_pool.elementAt(x);

      // If the PooledConnection is not in use, close it
      if ( pcon.inUse() == false ) { pcon.close();  }
      else
      {
        if (DEBUG)
        {
          System.out.println("--> Force close");
        }

        // If it still in use, sleep for 30 seconds and
        // force close.
        try
        {
          java.lang.Thread.sleep(30000);
          pcon.close();
        }
        catch (InterruptedException ie)
        {
          if (DEBUG) System.err.println(ie.getMessage());
        }
      }
    }

    if (DEBUG)
    {
      System.out.println("Exit Default Connection Pool, Finalize");
    }

    super.finalize();
  }

  /**
   * The Pool can be Enabled and Disabled. Disabling the pool
   * closes all the outstanding Unused connections and any new
   * connections will be closed upon release.
   * @param flag Control the Connection Pool. If it is enabled then Connections will actuall be held
   * around. If disabled then all unused connections will be instantly closed and as
   * connections are released they are closed and removed from the pool.
   * @return
   */
  public void setPoolEnabled( final boolean flag )
  {

  }


}