数据库连接池的实现(很完整(支持多种数据库

package test; import java.lang.reflect.Proxy; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.util.LinkedList; public class ConnectionPool { //ConnectionPool 中连接的个数 private int linkedNo = 0; //活动的个数 private int activeNo = 0; //驱动类 private String driver = null; //连接路径 private String url = null; //用户名 private String userName = null; //密码 private String password = null; //空闲的Connection private LinkedList<Connection> leisureConn = null; //使用中的Connection private LinkedList<Connection> usingConn = null; //线程池类的对象 private static ConnectionPool connectionPool = null; //封装好ConnectionPool对象 public static ConnectionPool newInstance(int linkedNo,String driver,String url,String userName,String password) { if(connectionPool == null) { connectionPool = new ConnectionPool(linkedNo,driver,url,userName,password); } return connectionPool; } //获取Connection池对象 public static ConnectionPool getInstance() { return connectionPool; } //初始化各个参数的值 private ConnectionPool(int linkedNo,String driver,String url,String userName,String password){ this.linkedNo = linkedNo; this.driver = driver; this.url = url; this.userName = userName; this.password = password; leisureConn = new LinkedList<Connection>(); usingConn = new LinkedList<Connection>(); } //获取数据库的连接 public synchronized Connection getConnection() { Connection conn = null; //判断可用连接是否为空，以及活动的个数是否大于可连接个数 if(leisureConn.isEmpty()&&activeNo==linkedNo) { try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } if(leisureConn.isEmpty()) { throw new NullPointerException("没有可用的连接对象"); } //从可用连接中获取一个连接对象 conn = leisureConn.getFirst(); leisureConn.removeFirst(); usingConn.addLast(conn); }else if(activeNo<linkedNo) { conn = buildConnection(driver, url, userName, password); //创建连接对象 usingConn.addLast(conn); //将其加入到使用连接集合中 activeNo++; return conn; }else { conn = usingConn.getFirst(); //从空闲连接中获取连接对象 usingConn.removeFirst(); // 从空闲连接中移除 usingConn.addLast(conn); //将其加入到使用连接集合中 } return conn; } public synchronized void closeConnection(Connection closeConn) { int i = 0; for(; i < usingConn.size(); i++) { Connection conn = usingConn.get(i); if(conn.equals(closeConn)) { break; } } if(i == usingConn.size()) throw new ClassCastException("你使用的连接不是我们这的..."); usingConn.remove(i); //从使用连接集合中删除连接对象 leisureConn.add(closeConn); // 将使用完毕的连接放回空闲连接集合中 } //建立连接，Connection池的建立 private Connection buildConnection(String driver,String url,String userName,String password) { Connection conn = null; Connection proxy = null; try { Class.forName(driver); } catch (ClassNotFoundException e) { e.printStackTrace(); } try { // System.out.println(url); conn = DriverManager.getConnection(url,userName,password); //调用反射机制来进行Close（）方法的处理。 proxy = (Connection)Proxy.newProxyInstance(conn.getClass().getClassLoader(), conn.getClass().getInterfaces(), new ConnectionInvocationHandler(conn)); } catch (SQLException e) { e.printStackTrace(); } return proxy; } }