package 动态连接数据库;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.lang.reflect.Proxy;import java.sql.Connection;import java.sql.DriverManager;import java.util.LinkedList;public class UtilsDB {    public static void main(String[] args) {        UtilsDB u = new UtilsDB();        System.err.println(u.getCon());    }    private static LinkedList
     
       pool = new LinkedList
      
       ();    static {        try {            Class.forName("com.mysql.jdbc.Driver");            String url = "jdbc:mysql:///abc";            for (int i = 0; i < 3; i++) {                // 真实对象                final Connection con = DriverManager.getConnection(url, "root",                        "1234");                // 声明代理                Object obj = Proxy.newProxyInstance(                        UtilsDB.class.getClassLoader(),                        new Class[] { Connection.class },                        new InvocationHandler() {                            @Override                            public Object invoke(Object proxy, Method method,                                    Object[] args) throws Throwable {                                if (method.getName().equals("close")) {                                    System.err.println("有人还连接");                                    synchronized (pool) {                                        pool.addLast((Connection) proxy);                                        pool.notifyAll();                                        return null;                                    }                                } else {                                    return method.invoke(con, args);                                }                            }                        });                // 将代理人添加到pool                pool.add((Connection) obj);            }        } catch (Exception e) {            throw new RuntimeException(e);        }    }    public static Connection getCon() {        synchronized (pool) {            if (pool.size() == 0) {                try {                    pool.wait();                } catch (Exception e) {                    throw new RuntimeException(e.getMessage());                }                return getCon();            } else {                Connection con = pool.removeFirst();                System.err.println("pool.size:" + pool.size());                return con;            }        }    }}
      
     

package 动态连接数据库;import java.sql.Connection;import java.sql.SQLException;import java.sql.Statement;public class TestDb {    public static void main(String[] args) {        //Connection con=UtilsDB.getCon();        //System.err.println(con);                            for (int i = 0; i < 110; i++) {            new Thread() {                public void run() {                    Connection con = UtilsDB.getCon();                    try {                        Statement st = con.createStatement();                        System.err.println(con + "\t" + this.getName() + "\t"                                + st);                    } catch (SQLException e) {                        e.printStackTrace();                    } finally {                        try {                            con.close();                        } catch (SQLException e) {                            // TODO Auto-generated catch block                            e.printStackTrace();                        }                    }                };            }.start();        }    }}