为什么 Mozilla 的这个 XMLHttpRequest 示例在 Firefox 3 中不起作用?

Why is this XMLHttpRequest sample from Mozilla is not working in Firefox 3?(为什么 Mozilla 的这个 XMLHttpRequest 示例在 Firefox 3 中不起作用?)

问题描述

我正在尝试从 Mozilla 获取使用 REST Web 服务以在 Firefox 3.0.10 下工作的示例代码.以下代码在 Firefox 中不起作用，但在 IE 8 中起作用！

I'm trying to get the sample code from Mozilla that consumes a REST web service to work under Firefox 3.0.10. The following code does NOT work in Firefox but does in IE 8!

1. 为什么这不起作用?
2. IE 8 是否支持 XMLHttpRequest?我见过的大多数例子都使用 ActiveX分配.我应该做什么?XMLHttpRequest 似乎更加标准化.

示例:

var req = new XMLHttpRequest();
req.open('GET', 'http://localhost/myRESTfulService/resource', false);    // throws 'undefined' exception
req.send(null);
if(req.status == 0)
  dump(req.responseText);

open 语句引发异常，描述为未定义".这很奇怪，因为我分配了 req 对象，在 Firefox 中运行它，并在调用 open 之前检查以确保它已定义(它说它是对象"类型).

The open statement is throwing an exception with the description 'undefined'. This is strange as I allocate the req object, am running it in Firefox, and checked to make sure it is defined before calling open (which it says it is of type 'object').

我也尝试过异步版本，但没有成功.

I've also tried the asynchronous version of this with no luck.

编辑 2:以下是我最近的代码:

function createRequestObject() {
    if( window.XMLHttpRequest ) {
        return new XMLHttpRequest();
    }
    else if( window.ActiveXObject ) {
        return new ActiveXObject( "Microsoft.XMLHTTP" );
    }

    return null;
}

function handleResponse( req ) {
    document.writeln( "Handling response..." );   // NEVER GETS CALLED
    if( req.readyState == 0 ) {
        document.writeln( "UNITIALIZED" );
    }
    else if( req.readyState == 1 ) {
        document.writeln( "LOADING" );
    }
    else if( req.readyState == 2 ) {
        document.writeln( "LOADED" );
    }
    else if( req.readyState == 3 ) {
        document.writeln( "INTERACTIVE" ); 
    }
    else if( req.readyState == 4 ) {
        document.writeln( "COMPLETE" );
        if( req.status == 200 ) {
            document.writeln( "SUCCESS" );
        }
    }
}

document.writeln( "" );
var req = createRequestObject();

try {
    document.writeln( "Opening service..." );
    req.onreadystatechange = function() { handleResponse( req ); };
    req.open('POST', 'http://localhost/test/test2.txt', true);  // WORKS IN IE8 & NOT FIREFOX


    document.writeln( "Sending service request..." );
    req.send('');

    document.writeln( "Done" );
}
catch( err ) {
    document.writeln( "ERROR: " + err.description );
}

编辑 3: 好的，我在 jQuery 中重新设计了这个.jQuery 在 IE 中运行良好，但从 Firefox 运行时会抛出未定义".我仔细检查并在 Firefox 中打开了启用 JavaScript" - 似乎在所有其他网页中都可以正常工作.下面是jQuery代码:

EDIT 3: Alright, I reworked this in jQuery. jQuery works great in IE but it throws 'Undefined' when running from Firefox. I double checked and 'Enable JavaScript' is turned on in Firefox - seems to work fine in all other web pages. Below is the jQuery code:

function handleResponse( resp ) {
    alert( "Name: " + resp.Name );
    alert( "URL: " + resp.URL );
}

$(document).ready( function() {
    $("a").click( function(event) {

        try {
            $.get( "http://localhost/services/ezekielservices/configservice/ezekielservices.svc/test", 
                   "{}",
                   function(data) { handleResponse( data ); },
                   "json" );
        } 
        catch( err ) {
            alert("'$.get' threw an exception: " + err.description);
        }

        event.preventDefault();
    });
} );    // End 'ready' check

解决方案总结:

好的，网络课101.我的问题确实是跨域的.我正在查看未发布的网站(仅在文件系统上)，该网站正在访问已发布的服务.当我在同一个域下发布我的网站时，它起作用了.

Alright, web lesson 101. My problem was indeed cross-domain. I was viewing my site unpublished (just on the file system) which was hitting a published service. When I published my site under the same domain it worked.

这也带来了 IE 和 Firefox 之间的一个重要区别.当IE遇到这种情况时，会提示用户是否接受跨域调用.Firefox 抛出异常.虽然我可以有一个例外，但更具描述性的例外会有所帮助.

Which also brings up an important distinction between IE and Firefox. When IE experiences this scenario, it prompts the user whether or not they accept the cross-domain call. Firefox throws an exception. While I'm fine with an exception, a more descriptive one would have been helpful.

感谢所有帮助过我的人.

Thanks for all those who helped me.

推荐答案

除非'http://www.mozilla.org/' 是此请求的来源域，由于同源策略，这将不起作用

unless 'http://www.mozilla.org/' is the domain from which this request originates, this wont work because of same origin policy

好的，好的状态是 200，而不是 0.

edit: Ok, a good status is 200, not 0.

查看 http://dogself.com/telluriumTest/ 并点击stackoverflow 测试".它使用您的代码并正常工作.

see http://dogself.com/telluriumTest/ and click on "stackoverflow test". its using your code and working.

特别是这段代码:

function test(){
    var req = new XMLHttpRequest();
    req.open('GET', 'index2.htm', false);    
    req.send(null);
    if(req.status == 200)
    alert("got some stuff back:"+req.responseText);
}

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