Safari双重提交ajax调用

Question

我注意到Safari 5.0.5(6533.21.1)似乎正在提交重复的ajax调用.当我运行以下简化测试用例时:

// jquery 1.6 include
$(document).ready(function() {
    setTimeout(function(e) {
        var req1 = $.getJSON('/api/private/customers.json');
        console.log('req1 sent');
    }, 2000);
    setTimeout(function(e) {
        var req2 = $.getJSON('/api/private/customers.json');
        console.log('req1 sent');
    }, 4000);
});

Safari资源面板和控制台显示两个xhr请求,但我的服务器日志显示三个xhr请求:

XX.XX.XX.XXX - - [10/May/2011:16:50:40 -0400] "GET /api/private/customers.json HTTP/1.1" 200 183 "https://sub.mydomain.com/customers" "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_7; en-us) AppleWebKit/533.21.1 (KHTML, like Gecko) Version/5.0.5 Safari/533.21.1"
XX.XX.XX.XXX - - [10/May/2011:16:50:42 -0400] "GET /api/private/customers.json HTTP/1.1" 200 183 "https://sub.mydomain.com/customers" "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_7; en-us) AppleWebKit/533.21.1 (KHTML, like Gecko) Version/5.0.5 Safari/533.21.1"
XX.XX.XX.XXX - - [10/May/2011:16:50:42 -0400] "GET /api/private/customers.json HTTP/1.1" 200 183 "https://sub.mycomain.com/customers" "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_7; en-us) AppleWebKit/533.21.1 (KHTML, like Gecko) Version/5.0.5 Safari/533.21.1"

当我使用最新版本的Firefox发出相同的请求时,我正确地收到了两个请求:

XX.XX.XX.XXX - - [10/May/2011:16:52:00 -0400] "GET /api/private/customers.json HTTP/1.1" 200 183 "https://sub.mycomain.com/customers" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:2.0.1) Gecko/20100101 Firefox/4.0.1"
XX.XX.XX.XXX - - [10/May/2011:16:52:02 -0400] "GET /api/private/customers.json HTTP/1.1" 200 183 "https://sub.mycomain.com/customers" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:2.0.1) Gecko/20100101 Firefox/4.0.1"

第一个请求似乎没有发生此行为,但所有后续请求都是一式两份发送的.有谁知道发生了什么事？在js中检测额外请求的努力是徒劳的.

Answer 1

我想我们不会知道这是错误还是功能...无论如何，Safari（如10.0.2版本）仍然按照Dan Manastireanu的说明执行条件请求。我发现请求没有重复的方式是使用当前请求时间设置标头。（或者，您也可以在url中添加一个timestamp参数，如Dan Manastireanu再次提到的那样）'If-Unmodified-Since'

我拒绝了，setRequestHeader('Connection', "close")因为这是一个禁止的标题名称，并抛出Refused to set unsafe header "Connection"错误。

因此，基本请求如下所示：

var get = function(url, callbackSucess, callbackError) {
    var request = new XMLHttpRequest();
    request.open('GET', url, true);
    request.timeout = 10000;

    var now = new Date().getTime();
    request.setRequestHeader('If-Unmodified-Since', now);

    request.onreadystatechange = function() {
        if (request.readyState !== 4) {
            return;
        }
        if (request.status === 200) {
            callbackSucess(request.status);
        } else {
            callbackError(request.status);
        }
    };
    request.onerror = function (error) {
        callbackError(error);
    };
    request.ontimeout = function () {
        request.abort();
    };
    request.send(null);
}

Answer 2

将Connection: Close标头添加到 API 响应可以修复该问题。