对象池模式(Pool)#
1. 目的#
**对象池模式**是一种提前准备了一组已经初始化了的对象『池』而不是按需创建或者销毁的创建型设计模式。对象池的客户端会向对象池中请求一个对象,然后使用这个返回的对象执行相关操作。当客户端使用完毕,它将把这个特定类型的工厂对象返回给对象池,而不是销毁掉这个对象。
在初始化实例成本高,实例化率高,可用实例不足的情况下,对象池可以极大地提升性能。在创建对象(尤其是通过网络)时间花销不确定的情况下,通过对象池在可期时间内就可以获得所需的对象。
无论如何,对象池模式在需要耗时创建对象方面,例如创建数据库连接,套接字连接,线程和大型图形对象(比方字体或位图等),使用起来都是大有裨益的。在某些情况下,简单的对象池(无外部资源,只占内存)可能效率不高,甚至会有损性能。
2. UML 类图#
3. 代码#
你可以在 GitHub 上找到这些例子
WorkerPool.php
<?php
namespace DesignPatterns\Creational\Pool;
class WorkerPool implements \Countable
{
/**
* @var StringReverseWorker[]
*/
private $occupiedWorkers = [];
/**
* @var StringReverseWorker[]
*/
private $freeWorkers = [];
public function get(): StringReverseWorker
{
if (count($this->freeWorkers) == 0) {
$worker = new StringReverseWorker();
} else {
$worker = array_pop($this->freeWorkers);
}
$this->occupiedWorkers[spl_object_hash($worker)] = $worker;
return $worker;
}
public function dispose(StringReverseWorker $worker)
{
$key = spl_object_hash($worker);
if (isset($this->occupiedWorkers[$key])) {
unset($this->occupiedWorkers[$key]);
$this->freeWorkers[$key] = $worker;
}
}
public function count(): int
{
return count($this->occupiedWorkers) + count($this->freeWorkers);
}
}
StringReverseWorker.php
<?php
namespace DesignPatterns\Creational\Pool;
class StringReverseWorker
{
/**
* @var \DateTime
*/
private $createdAt;
public function __construct()
{
$this->createdAt = new \DateTime();
}
public function run(string $text)
{
return strrev($text);
}
}
4. 测试#
Tests/PoolTest.php
<?php
namespace DesignPatterns\Creational\Pool\Tests;
use DesignPatterns\Creational\Pool\WorkerPool;
use PHPUnit\Framework\TestCase;
class PoolTest extends TestCase
{
public function testCanGetNewInstancesWithGet()
{
$pool = new WorkerPool();
$worker1 = $pool->get();
$worker2 = $pool->get();
$this->assertCount(2, $pool);
$this->assertNotSame($worker1, $worker2);
}
public function testCanGetSameInstanceTwiceWhenDisposingItFirst()
{
$pool = new WorkerPool();
$worker1 = $pool->get();
$pool->dispose($worker1);
$worker2 = $pool->get();
$this->assertCount(1, $pool);
$this->assertSame($worker1, $worker2);
}
}
原文:
最后更新: 2018年8月4日 13:04:18