使用RMI建立数据库连接池

import java.io.PrintWriter; import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.lang.reflect.Proxy; import java.rmi.RemoteException; import java.rmi.server.UnicastRemoteObject; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.util.ArrayList; import java.util.Iterator; import java.util.List; import javax.naming.NameAlreadyBoundException; import javax.naming.NameNotFoundException; import javax.sql.DataSource; public class DataSourceImpl extends UnicastRemoteObject implements DataSource, DataPool{ private ConnectionParam connParam = null ; private List<_Connection> conns = new ArrayList<_Connection>() ; private int connectionCount = 0 ; public DataSourceImpl(ConnectionParam connParam) throws RemoteException{ this.connParam = connParam; } public DataSourceImpl() throws RemoteException{ System.out.println("new !"); } public void initConnection(){ connParam.setDriver("com.mysql.jdbc.Driver") ; try { Class.forName(connParam.getDriver()); } catch (ClassNotFoundException e) { e.printStackTrace(); } connParam.setMaxConnection(10); connParam.setMinConnection(0); connParam.setUrl("jdbc:mysql://localhost:3306/test") ; } public Connection getConnection() throws SQLException { //首先从连接池中找出空闲的对象 Connection conn = getFreeConnection(0); if(conn == null){ //判断是否超过最大连接数,如果超过最大连接数 //则等待一定时间查看是否有空闲连接,否则抛出异常告诉用户无可用连接 if(getConnectionCount() >= connParam.getMaxConnection()){ conn = getFreeConnection(connParam.getWaitTime()); } else{//没有超过连接数，重新获取一个数据库的连接 connParam.setUser("root"); connParam.setPassword("cpc"); // System.out.println(connParam.getUrl()); Connection conn2 = DriverManager.getConnection(connParam.getUrl(), "root", "cpc"); //代理将要返回的连接对象 _Connection _conn = new _Connection(conn2,true); synchronized(conns){ conns.add(_conn); } conn = _conn.getConnection(); } } connectionCount++ ; return conn; } private int getConnectionCount() { return connectionCount; } protected synchronized Connection getFreeConnection(long nTimeout) throws SQLException { Connection conn = null; Iterator iter = conns.iterator(); while(iter.hasNext()){ _Connection _conn = (_Connection)iter.next(); if(!_conn.isInUse()){ conn = _conn.getConnection(); _conn.setInUse(true); break; } } if(conn == null && nTimeout > 0){ //等待nTimeout毫秒以便看是否有空闲连接 try{ Thread.sleep(nTimeout); }catch(Exception e){} conn = getFreeConnection(0); if(conn == null) throw new SQLException("没有可用的数据库连接"); } return conn; } /* (non-Javadoc) * @see poolInOther.DataSource#customerCome() */ /* (non-Javadoc) * @see poolInOther.DataPool#customerCome() */ public void customerCome() throws RemoteException{ System.out.println("a customer come"); ConnectionParam cp = new ConnectionParam(); DataSource ds = null ; try { ds = ConnectionFactory.bind("mysql", cp); } catch (NameAlreadyBoundException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } catch (InstantiationException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } try { Connection con = ConnectionFactory.lookup("mysql").getConnection(); System.out.println(con); } catch (Exception e) { e.printStackTrace(); } } public void customerOut() throws RemoteException { // TODO Auto-generated method stub try { System.out.println("customer out"); ((DataSourceImpl)(ConnectionFactory.lookup("mysql"))).close(); } catch (NameNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public PrintWriter getLogWriter() throws SQLException { return null; } public int getLoginTimeout() throws SQLException { return 0; } public void setLogWriter(PrintWriter arg0) throws SQLException { } public void setLoginTimeout(int arg0) throws SQLException { } public boolean isWrapperFor(Class<?> arg0) throws SQLException { return false; } public <T> T unwrap(Class<T> arg0) throws SQLException { return null; } class _Connection implements InvocationHandler { private final static String CLOSE_METHOD_NAME = "close"; private Connection conn = null; //数据库的忙状态 private boolean inUse = false; //用户最后一次访问该连接方法的时间 private long lastAccessTime = System.currentTimeMillis(); _Connection(Connection conn, boolean inUse){ this.conn = conn; this.inUse = inUse; } /** * Returns the conn. * @return Connection */ public Connection getConnection() { //返回数据库连接conn的接管类，以便截住close方法 // System.out.println(Proxy.newProxyInstance( // conn.getClass().getClassLoader(), // conn.getClass().getInterfaces(),this)); Connection conn2 = (Connection)Proxy.newProxyInstance( conn.getClass().getClassLoader(), conn.getClass().getInterfaces(),this); return conn2; } /** * 该方法真正的关闭了数据库的连接 * @throws SQLException */ void close() throws SQLException{ //由于类属性conn是没有被接管的连接，因此一旦调用close方法后就直接关闭连接 connectionCount-- ; conn.close(); } /** * Returns the inUse. * @return boolean */ public boolean isInUse() { return inUse; } /** * @see java.lang.reflect.InvocationHandler#invoke(java.lang.Object, java.lang.reflect.Method, java.lang.Object) */ public Object invoke(Object proxy, Method m, Object[] args) throws Throwable { Object obj = null; //判断是否调用了close的方法，如果调用close方法则把连接置为无用状态 if(CLOSE_METHOD_NAME.equals(m.getName())) setInUse(false); else obj = m.invoke(conn, args); //设置最后一次访问时间，以便及时清除超时的连接 lastAccessTime = System.currentTimeMillis(); return obj; } /** * Returns the lastAccessTime. * @return long */ public long getLastAccessTime() { return lastAccessTime; } /** * Sets the inUse. * @param inUse The inUse to set */ public void setInUse(boolean inUse) { this.inUse = inUse; } } public void stop() { } public int close() throws SQLException { int cc = 0; SQLException excp = null; Iterator iter = conns.iterator(); while(iter.hasNext()){ try{ _Connection con = (_Connection)iter.next(); con.close(); con.setInUse(false); cc ++; }catch(Exception e){ if(e instanceof SQLException) excp = (SQLException)e; } } if(excp != null) throw excp; return cc; } @Override public Connection getConnection(String username, String password) throws SQLException { // TODO Auto-generated method stub return null; } }