dbconnectionmanager.java

cmpp2.0的网关 java源码

 * @param props The connection pool properties
 */
    private void loadDrivers(Properties props) {
      String driverClasses = props.getProperty("drivers");
      StringTokenizer st = new StringTokenizer(driverClasses);
      while (st.hasMoreElements()) {
          String driverClassName = st.nextToken().trim();
           try {
              Driver driver = (Driver)
                Class.forName(driverClassName).newInstance();
                DriverManager.registerDriver(driver);
                drivers.addElement(driver);
                Log.printEvent("Registered JDBC driver " + driverClassName,logFile);
            }
            catch (Exception e) {
                  Log.printEvent("Can't register JDBC driver: " +
                  driverClassName + ", Exception: " + e,logFile);
            }
      }
    }

/**
 * 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;                          //已用连接数
        private Vector freeConnections = new Vector();  //可用连接数
        private int maxConn;                            //最大连接数
        private int minConn;                            //最小连接数
        private int defaultConn;                        //默认连接数
        private String name;                            //数据库名称
        private String password;                        //登陆密码
        private String URL;                             //数据库路径
        private String user;                           //用户名称

        public int getUsedConNum(){
            return checkedOut;
        }
        public int getFreeConNum(){
            return freeConnections.size();
        }
/**
 * 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,int minConn,int defaultConn) {
          this.name        = name;
          this.URL         = URL;
          this.user        = user;
          this.password    = password;
          this.maxConn     = maxConn;
          this.minConn     = minConn;
          this.defaultConn =defaultConn;
          initConnections();
    }
/**
 * 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
            int free=freeConnections.size();
            if(con==null||((checkedOut + free > maxConn) && (free >=minConn)) ) {
                try{
                    if(con!=null){
                        con.close();
                        Log.printEvent("Closed connection for pool " + name,logFile);
                    }
                    else
                        Log.printEvent("Thread Name :"+Thread.currentThread().getName()+" Closed Connecion is null " + name,logFile);
                }catch(SQLException e){
                    Log.printEvent("Can't close connection for pool " + name+" Exception :"+e,logFile);
                }
            } else {
                Statement stmt=null;
                try{
                        if(!con.getAutoCommit())
                                con.setAutoCommit(true);
                        stmt=con.createStatement();
                        stmt.close();
                        freeConnections.addElement(con);
                }catch(Exception e){
                        if(stmt!=null){
                            try{
                                 stmt.close();
                                 con.close();
                            }
                            catch(SQLException ex){}
                         }
                }
            }
            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 java.sql.Connection getConnection() {
        java.sql.Connection con = null;
        if (freeConnections.size() > 0) {
                    con = (java.sql.Connection) freeConnections.firstElement();
                    freeConnections.removeElementAt(0);
                    Statement stmt=null;
                    try {

                        if (con==null||con.isClosed()) {
                        Log.printEvent("Removed bad connection from 1 in:" + Thread.currentThread().getName(),logFile);

                        con = getConnection();
                        }else{
                            stmt=con.createStatement();
                            stmt.close();
                        }
                    }
                    catch (SQLException e) {
                        Log.printEvent("Removed bad connection from 2 in:" +Thread.currentThread().getName(),logFile);
                        if(stmt!=null){
                            try{
                                 stmt.close();
                                 con.close();
                            }
                            catch(SQLException ex){}
                         }
                         con = getConnection();
                     }
          }
          else if (maxConn == 0 || checkedOut < maxConn) {         //如果maxCon为零则可无限增大

              con = newConnection();
          }
          if (con != null) {
            checkedOut++;
          }
        return con;
    }

/**
 * 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.
 * <P>
 * If no connection is available and the max number has been
 * reached, this method waits the specified time for one to be
 * checked in.
 *
 * @param timeout The timeout value in milliseconds
 */
    public synchronized java.sql.Connection getConnection(long timeout) {
        long startTime = new Date().getTime();
        java.sql.Connection con;
        while ((con = getConnection()) == null) {
            try {
                wait(timeout);                                         //有notifyAll()唤醒或时间到自动唤醒
            }
            catch (InterruptedException e) {}
            if ((new Date().getTime() - startTime) >= timeout) {
  // Timeout has expired
                  return null;
              }
        }
        return con;
    }

/**
 * Closes all available connections.
 */
      public synchronized void release() {
           Enumeration allConnections = freeConnections.elements();
           while (allConnections.hasMoreElements()) {
              java.sql.Connection con = (java.sql.Connection) allConnections.nextElement();
              try {
                  con.close();
                  Log.printEvent("Closed connection for pool " + name,logFile);
              }
              catch (SQLException e) {
                  Log.printEvent( "Can't close connection for pool " + name+" Exception :"+e,logFile);
              }
            }
            freeConnections.removeAllElements();
      }

/**
 * Creates a new connection, using a userid and password
 * if specified.
 */
      private java.sql.Connection newConnection()  {
          java.sql.Connection con = null;
          try {
              if (user == null) {
                  con = DriverManager.getConnection(URL);
              }
              else {
                  con = DriverManager.getConnection(URL,user,password);
              }
              Log.printEvent("Created a new connection in pool " + name,logFile);
          }
          catch (SQLException e) {
                Log.printEvent( "Can't create a new connection for " + URL+" Exception :"+e,logFile);
                return null;
          }
          return con;
      }

      private void initConnections(){
          java.sql.Connection con = null;
          for(int i=0;i<defaultConn;i++){
              con=newConnection();
              freeConnections.addElement(con);
          }
      }
  }
}