在网上看到了有些同志提到了为Ajax的XMLHttpRequest提供一个对象池，也读了他们给出的实现代码。感觉不是特别理想，于是模仿apache的commons中的ObjectPool的思路写了一个简单的JavaScript版。望指教:
function ObjectPool(poolableObjectFactory) {
this ._poolableObjectFactory = poolableObjectFactory;
this ._idlePool = [];
this ._activePool = [];
}
// 从对象池中租借一个对象，如果目前没有可用的空闲对象则通过poolableObjectFactory创建一个
// 既然是借的，用完记得一定要还哦！
ObjectPool.prototype.borrowObject = function () {
var object = null ;
var idlePool = this ._idlePool;
var factory = this ._poolableObjectFactory;
if (idlePool.length > 0 ) {
object = idlePool.pop();
}
else {
object = factory.makeObject();
}
if (object != null ) {
this ._activePool.push(object);
if (factory.activateObject) {
factory.activateObject(object);
}
}
return object;
}
// 归还一个对象
ObjectPool.prototype.returnObject = function (object) {
function indexOf(array, object) {
for ( var i = 0 ; i < array.length; i ++ ) {
if (array[i] == object) return i;
}
return - 1 ;
}
if (object != null ) {
var activePool = this ._activePool;
var factory = this ._poolableObjectFactory;
var i = indexOf(activePool, object);
if (i < 0 ) return ;
if (factory.passivateObject) {
factory.passivateObject(object);
}
activePool.splice(i, 1 );
this ._idlePool.push(object);
}
}
// 返回当前激活对象的个数
ObjectPool.prototype.getNumActive = function () {
return this ._activePool.length;
}
// 返回当前空闲对象的个数
ObjectPool.prototype.getNumIdle = function () {
return this ._idlePool.length;
}
// 销毁对象池及其中的所有对象
// 如果对象池中的对象需要析构。那么必须实现poolableObjectFactory中的destroyObject方法，同时保证ObjectPool的destroy方法在需要的时候被调用到（例如Window的unload事件中）。
ObjectPool.prototype.destroy = function () {
var factory = this ._poolableObjectFactory;
function returnObject(object) {
if (factory.passivateObject) {
factory.passivateObject(object);
}
}
function destroyObject(object) {
if (factory.destroyObject) {
factory.destroyObject(object);
}
}
var activePool = this ._activePool;
for ( var i = 0 ; i < activePool.length; i ++ ) {
var object = activePool[i];
returnObject(object);
destroyObject(object);
}
var idlePool = this ._idlePool;
for ( var i = 0 ; i < idlePool.length; i ++ ) {
var object = idlePool[i];
destroyObject(object);
}
this ._idlePool = null ;
this ._activePool = null ;
this ._poolableObjectFactory = null ;
}
上面代码中ObjectPool的构造参数poolableObjectFactory的声明如下:
// 注意: 这只是说明，不是真正的代码！
var PoolableObjectFactory = {
makeObject: function () {} , // 创建一个新的对象。(必须声明)
activateObject: function (object) {} , // 当一个对象被激活时(即被借出时)触发的方法。(可选)
passivateObject: function (object) {} , // 当一个对象被钝化时(即被归还时)触发的方法。(可选)
destroyObject: function (object) {} // 销毁一个对象。(可选)
} ;
结合XMLHttpRequest创建过程的简陋示例：
// 声明XMLHttpRequest的创建工厂
var factory = {
makeObject: function () {
// 创建XMLHttpRequset对象
if (window.ActiveXObject) {
return new ActiveXObject( " Microsoft.XMLHTTP " );
}
else {
return new XMLHttpRequest();
}
} ,
passivateObject: function (xhr) {
// 重置XMLHttpRequset对象
xhr.onreadystatechange = {} ;
xhr.abort();
}
} ;
var pool = new ObjectPool(factory); // 创建对象池
//
var xhr = pool.borrowObject(); // 获得一个XMLHttpRequest对象
xhr.onreadystatechange = function () {
if (xhr.readyState == 4 ) {
//
pool.returnObject(xhr); // 归还XMLHttpRequest对象
}
} ;
xhr.open(method, url, true );
//
最后附上jsUnit的测试用例:
function test_pool() {
var factory = {
counter: 0 ,
makeObject: function () {
return {id: ++ this .counter} ;
} ,
activateObject: function (object) {
object.activated = true ;
} ,
passivateObject: function (object) {
object.activated = false ;
} ,
destroyObject: function (object) {
object.destroyed = true ;
}
} ;
var pool = new ObjectPool(factory);
// borrowObject object1
var object1 = pool.borrowObject();
assertEquals(object1.id, 1 );
assertTrue(object1.activated);
assertEquals(factory.counter, 1 );
assertEquals(pool.getNumActive(), 1 );
assertEquals(pool.getNumIdle(), 0 );
// borrowObject object2
var object2 = pool.borrowObject();
assertEquals(object2.id, 2 );
assertTrue(object2.activated);
assertEquals(factory.counter, 2 );
assertEquals(pool.getNumActive(), 2 );
assertEquals(pool.getNumIdle(), 0 );
// borrowObject object3
var object3 = pool.borrowObject();
assertEquals(object3.id, 3 );
assertTrue(object3.activated);
assertEquals(factory.counter, 3 );
assertEquals(pool.getNumActive(), 3 );
assertEquals(pool.getNumIdle(), 0 );
// returnObject object2
pool.returnObject(object2);
assertFalse(object2.activated);
assertEquals(factory.counter, 3 );
assertEquals(pool.getNumActive(), 2 );
assertEquals(pool.getNumIdle(), 1 );
// returnObject object3
pool.returnObject(object3);
assertFalse(object3.activated);
assertEquals(pool.getNumActive(), 1 );
assertEquals(pool.getNumIdle(), 2 );
// returnObject object1
pool.returnObject(object1);
assertFalse(object1.activated);
assertEquals(pool.getNumActive(), 0 );
assertEquals(pool.getNumIdle(), 3 );
// destroy the pool
pool.destroy();
assertTrue(object1.destroyed);
assertTrue(object2.destroyed);
assertTrue(object3.destroyed);
}
下载: http://www.blogjava.net/Files/bennybao/pool.rar
Feedback
# re: 为Ajax的XMLHttpRequest提供对象池(模仿Apache中ObjectPool的实现) 回复 更多评论
2007-02-10 01:46 by ghf
好
# re: 为Ajax的XMLHttpRequest提供对象池(模仿Apache中ObjectPool的实现) 回复 更多评论
2007-02-16 11:18 by 张沈鹏
为什么要一个activePool ,没有什么用处呀,用完了直接push进入idle,用的时候直接从idle中pop,同时把xmlrequest封装一下,让他自动来pop和push,用只要给出url和recall就可以了
我的邮箱是[email protected]欢迎探讨
__reqPool={
idle:[],
new:function(){
var r=this.idle.pop();
if(!r){
if (window.XMLHttpRequest)r=new XMLHttpRequest();
else{
try{r=new ActiveXObject("Msxml2.XMLHTTP");}
catch(e){r=new ActiveXObject("Microsoft.XMLHTTP");}
}
}
return r;
}
open:function(url,recall,error){
var http=this.new();
http.open("GET",url,true);
http.onreadystatechange=function(){
if(http.readyState==4)
{
if(http.status==200)recall(http.responseText.toString());
else if(error) error(http.status,http.responseText.toString());
idle.push(http);
}
};
}
}
# re: 为Ajax的XMLHttpRequest提供对象池(模仿Apache中ObjectPool的实现)[未登录] 回复 更多评论
2007-02-16 13:57 by BennyBao
@张沈鹏
activePool确实不是必须的，但是有了activePool之后就可以很方便的知道究竟有多少已激活的Object，或者可以利用一个类似“守护线程”的定时器来监控每个Object的激活时间，以便与实现类似超时之类的功能。
另外需要说明的是，根据我的本意，这里的ObjectPool并不只为XMLHttp设计。
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