动态代理连接数据库

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<Connection> pool = new LinkedList<Connection>();
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();
}
}

}

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