[javaEE] 数据库连接池和动态代理

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;

public class JDBCTest {
    public static void main(String[] args) throws Exception {
        //使用反射的方式
        Class.forName("com.mysql.jdbc.Driver");
        //获取数据库连接，导包的时候，注意要导java.sql下的，面向接口编程
        MyPool pool=new MyPool();
        Connection conn=pool.getConnection();
        //获取传输器对象
        Statement statement=conn.createStatement();
        //获取结果集对象
        ResultSet resultSet=statement.executeQuery("select * from user");
        //遍历
        while(resultSet.next()){
            String username=resultSet.getString("username");
            System.out.println(username);
        }
        //关闭资源
        resultSet.close();
        statement.close();
        pool.resetConn(conn);
        
    }
}

import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.LinkedList;
import java.util.List;
import java.util.logging.Logger;

import javax.sql.DataSource;

/**
 * 手写连接池
 * 
 * @author taoshihan
 * 
 */
public class MyPool implements DataSource {
    // 连接池
    public static List<Connection> pool = new LinkedList<Connection>();
    // 初始化
    static {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            for (int i = 0; i < 5; i++) {
                Connection conn = DriverManager.getConnection(
                        "jdbc:mysql://localhost:3306/java", "root", "root");
                pool.add(conn);
            }
        } catch (Exception e) {
        }
    }

    /**
     * 获取连接
     */
    @Override
    public Connection getConnection() throws SQLException {
        // 如果池中没有连接
        if (pool.size() == 0) {
            for (int i = 0; i < 5; i++) {
                Connection conn = DriverManager.getConnection(
                        "jdbc:mysql://localhost:3306/java", "root", "root");
                pool.add(conn);
            }
        }
        //先进先出
        Connection conn=pool.remove(0);
        System.out.println("获取一个连接，池里还剩余"+pool.size());
        return conn;
    }
    /**
     * 重置连接
     */
    public void resetConn(Connection conn){
        try {
            if(conn!=null && !conn.isClosed()){
                pool.add(conn);
                System.out.println("还回一个连接，池里还剩余"+pool.size());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    @Override
    public Connection getConnection(String username, String password)
            throws SQLException {
                return null;
    }

    @Override
    public PrintWriter getLogWriter() throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void setLogWriter(PrintWriter out) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public void setLoginTimeout(int seconds) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public int getLoginTimeout() throws SQLException {
        // TODO Auto-generated method stub
        return 0;
    }

    @Override
    public Logger getParentLogger() throws SQLFeatureNotSupportedException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public boolean isWrapperFor(Class<?> iface) throws SQLException {
        // TODO Auto-generated method stub
        return false;
    }

}

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;

public class JDBCTest {
    public static void main(String[] args) throws Exception {
        
        //测试装饰模式
        Animal dog=new BigDog(new Dog());
        dog.eat();
        dog.sound();

    }
}

/**
 * 装饰模式测试
 * @author taoshihan
 *
 */
interface Animal{
    public void eat();
    public void sound();
}
class Dog implements Animal{

    @Override
    public void eat() {
        System.out.println("吃");
    }

    @Override
    public void sound() {
        System.out.println("汪");
    }
}
//此时我想修改Dog类中的sound方法
class BigDog implements Animal{
    private Dog dog;
    public BigDog(Dog dog) {
        this.dog=dog;
    }
    /**
     * 这个方法调原来的
     */
    @Override
    public void eat() {
        dog.eat();
    }
    /**
     * 这个方法进行装饰
     */

    @Override
    public void sound() {
        System.out.println("大叫");
    }
    
}

        
        //测试代理模式
        final Dog dog=new Dog();
        Animal proxy=(Animal) Proxy.newProxyInstance(Dog.class.getClassLoader(),Dog.class.getInterfaces() , new InvocationHandler() {
            
            @Override
            public Object invoke(Object proxy, Method method, Object[] args)
                    throws Throwable {
                if("sound".equals(method.getName())){
                    System.out.println("大叫");
                    return null;
                }else{
                    return method.invoke(dog, args);
                }
            }
        });
        proxy.eat();
        proxy.sound();