[javaEE] 数据库连接池和动态代理详解编程语言

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();