ConnectionPool原理

ConnectionPool原理：

public class MyDataSource {
   private static String url = "jdbc:mysql://localhost:3306/jdbc";
  private static String user = "root";
  private static String password = "";

  private static int initCount = 5;
  private static int maxCount = 10;
  private int currentCount = 0;

  LinkedList<Connection> connectionsPool = new LinkedList<Connection>();

  public MyDataSource() {
    try {
      for (int i = 0; i < initCount; i++) {
        this.connectionsPool.addLast(this.createConnection());
        this.currentCount++;
      }
    } catch (SQLException e) {
      throw new ExceptionInInitializerError(e);
    }
  }

  public Connection getConnection() throws SQLException {
    synchronized (connectionsPool) {
      if (this.connectionsPool.size() > 0)
        return this.connectionsPool.removeFirst();

      if (this.currentCount < maxCount) {
        this.currentCount++;
        return this.createConnection();
      }

      throw new SQLException("已没有链接");
    }
  }

  public void free(Connection conn) {
    this.connectionsPool.addLast(conn);
  }

  private Connection createConnection() throws SQLException {
    return DriverManager.getConnection(url, user, password);
  }
}