blocks|key|1192331|text|您只需在$.ajax({})中的某个位置添加：timeout:+<number+of+miliseconds>,即可。此外，在一些情况下，cache:+false,可能会有所帮助。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1192332|$.ajax+is+well+documented，你应该检查那里的选项，可能会发现一些有用的东西。|1192333|祝好运!|1192334|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.jquery.com/Ajax/jQuery.ajax#toptions^0|4|A|N|X|1X|D|0|0|P|0|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Y|8|@]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|H|3|I|5|6|7|12|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|K|$L|$5|M|N|O|E|$P|Q]]]]

You should just add: <code>timeout: &lt;number of miliseconds&gt;,</code> somewhere within <code>$.ajax({})</code>.
Also, <code>cache: false,</code> might help in a few scenarios.

<a href="http://docs.jquery.com/Ajax/jQuery.ajax#toptions" rel="noreferrer">$.ajax is well documented</a>, you should check options there, might find something useful.

Good luck!

blocks|key|1407755|text|你试过这个吗？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1407756|$(document).ajaxError(function(){+alert('error');+}|code-block|syntax|javascript|1407757|它应该可以处理所有的AjaxErrors。我已经找到了here。在那里，您还可以将这些错误写入firebug控制台。|offset|length|1407758|entityMap|0|LINK|mutability|MUTABLE|url|http://www.thefutureoftheweb.com/blog/hidden-ajax-errors-in-jquery^0|0|0|R|4|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

Have you tried this?

<pre><code>$(document).ajaxError(function(){ alert('error'); }
</code></pre>

That should handle all AjaxErrors. I´ve found it <a href="http://www.thefutureoftheweb.com/blog/hidden-ajax-errors-in-jquery" rel="nofollow noreferrer">here</a>.
There you find also a possibility to write these errors to your firebug console.

blocks|key|1192411|text|因为我不能重复这个问题，所以我只能建议在ajax调用超时的情况下尝试。在jQuery中，您可以使用$.ajaxSetup设置它(并且它对所有$.ajax调用都是全局的)，或者您可以专门为您的调用设置它，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1192412|$.ajax({
++++type:+'GET',
++++url:+'http://www.mywebapp.com/keepAlive',
++++timeout:+15000,
++++success:+function(data)+{},
++++error:+function(XMLHttpRequest,+textStatus,+errorThrown)+{}
})|code-block|syntax|javascript|1192413|JQuery将为您的调用注册一个15秒的超时时间；此后，如果没有来自服务器的http响应代码，jQuery将执行错误回调，并将textStatus值设置为"+timeout“。这样，您至少可以停止ajax调用，但无法将实际的网络问题与连接丢失区分开来。|1192414|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Since I can't duplicate the issue I can only suggest to try with a timeout on the ajax call. In jQuery you can set it with the $.ajaxSetup (and it will be global for all your $.ajax calls) or you can set it specifically for your call like this:

<pre><code>$.ajax({
 type: 'GET',
 url: 'http://www.mywebapp.com/keepAlive',
 timeout: 15000,
 success: function(data) {},
 error: function(XMLHttpRequest, textStatus, errorThrown) {}
})
</code></pre>

JQuery will register a 15 seconds timeout on your call; after that without an http response code from the server jQuery will execute the error callback with the textStatus value set to "timeout". With this you can at least stop the ajax call but you won't be able to differentiate the real network issues from the loss of connections.

blocks|key|1192471|text|我在本例中看到的是，如果我拉出客户机的网线并进行调用，就会调用ajax成功处理程序(为什么，我不知道)，并且data参数是一个空字符串。因此，如果你考虑了真正的错误处理，你可以这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1192472|function+handleError(jqXHR,+textStatus,+errorThrown)+{
++++...
}

jQuery.ajax({
++++...
++++success:+function(data,+textStatus,+jqXHR)+{
++++++++if+(data+==+"")+handleError(jqXHR,+"clientNetworkError",+"");
++++},
++++error:+handleError
});|code-block|syntax|javascript|1192473|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

What I see in this case is that if I pull the client machine's network cable and make the call, the ajax success handler is called (why, I don't know), and the data parameter is an empty string. So if you factor out the real error handling, you can do something like this:

<pre><code>function handleError(jqXHR, textStatus, errorThrown) {
 ...
}

jQuery.ajax({
 ...
 success: function(data, textStatus, jqXHR) {
 if (data == "") handleError(jqXHR, "clientNetworkError", "");
 },
 error: handleError
});
</code></pre>

blocks|key|1192496|text|如果您正在进行跨域操作，请调用Use+Jsonp。否则不返回错误。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1192497|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

If you are making cross domain call the Use Jsonp. else the error is not returned.

blocks|key|1192499|text|//+start+snippet
error:+function(XMLHttpRequest,+textStatus,+errorThrown)+{
++++++++if+(XMLHttpRequest.readyState+==+4)+{
++++++++++++//+HTTP+error+(can+be+checked+by+XMLHttpRequest.status+and+XMLHttpRequest.statusText)
++++++++}
++++++++else+if+(XMLHttpRequest.readyState+==+0)+{
++++++++++++//+Network+error+(i.e.+connection+refused,+access+denied+due+to+CORS,+etc.)
++++++++}
++++++++else+{
++++++++++++//+something+weird+is+happening
++++++++}
++++}
//end+snippet|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1192500|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>// start snippet
error: function(XMLHttpRequest, textStatus, errorThrown) {
 if (XMLHttpRequest.readyState == 4) {
 // HTTP error (can be checked by XMLHttpRequest.status and XMLHttpRequest.statusText)
 }
 else if (XMLHttpRequest.readyState == 0) {
 // Network error (i.e. connection refused, access denied due to CORS, etc.)
 }
 else {
 // something weird is happening
 }
 }
//end snippet
</code></pre>

blocks|key|1192533|text|使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1192534|xhr.onerror+=+function(e){
++++if+(XMLHttpRequest.readyState+==+4)+{
++++++++//+HTTP+error+(can+be+checked+by+XMLHttpRequest.status+and+XMLHttpRequest.statusText)
++++++++selFoto.erroUploadFoto('Erro+HTTP:+'%2BXMLHttpRequest.statusText);
++++}
++++else+if+(XMLHttpRequest.readyState+==+0)+{
++++++++//+Network+error+(i.e.+connection+refused,+access+denied+due+to+CORS,+etc.)
++++++++selFoto.erroUploadFoto('Erro+de+rede:'%2BXMLHttpRequest.statusText);
++++}
++++else+{
++++++++selFoto.erroUploadFoto('Erro+desconhecido.');
++++}

};|code-block|syntax|javascript|1192535|(更多代码如下-上传图像示例)|1192536|var+selFoto+=+{
+++foto:+null,

+++upload:+function(){
++++++++LoadMod.show();

++++++++var+arquivo+=+document.frmServico.fileupload.files[0];
++++++++var+formData+=+new+FormData();

++++++++if+(arquivo.type.match('image.*'))+{
++++++++++++formData.append('upload',+arquivo,+arquivo.name);

++++++++++++var+xhr+=+new+XMLHttpRequest();
++++++++++++xhr.open('POST',+'FotoViewServlet?acao=uploadFoto',+true);
++++++++++++xhr.responseType+=+'blob';

++++++++++++xhr.onload+=+function(e){
++++++++++++++++if+(this.status+==+200)+{
++++++++++++++++++++selFoto.foto+=+this.response;
++++++++++++++++++++var+url+=+window.URL+%7C%7C+window.webkitURL;
++++++++++++++++++++document.frmServico.fotoid.src+=+url.createObjectURL(this.response);
++++++++++++++++++++$('#foto-id').show();
++++++++++++++++++++$('#div_upload_foto').hide();+++++++++++
++++++++++++++++++++$('#div_master_upload_foto').css('background-color','transparent');
++++++++++++++++++++$('#div_master_upload_foto').css('border','0');

++++++++++++++++++++Dados.foto+=+document.frmServico.fotoid;
++++++++++++++++++++LoadMod.hide();
++++++++++++++++}
++++++++++++++++else{
++++++++++++++++++++erroUploadFoto(XMLHttpRequest.statusText);
++++++++++++++++}

++++++++++++++++if+(XMLHttpRequest.readyState+==+4)+{
+++++++++++++++++++++selFoto.erroUploadFoto('Erro+HTTP:+'%2BXMLHttpRequest.statusText);
++++++++++++++++}
++++++++++++++++else+if+(XMLHttpRequest.readyState+==+0)+{
+++++++++++++++++++++selFoto.erroUploadFoto('Erro+de+rede:'%2BXMLHttpRequest.statusText);+++++++++++++++++++++++++++++
++++++++++++++++}

++++++++++++};

++++++++++++xhr.onerror+=+function(e){
++++++++++++if+(XMLHttpRequest.readyState+==+4)+{
++++++++++++++++//+HTTP+error+(can+be+checked+by+XMLHttpRequest.status+and+XMLHttpRequest.statusText)
++++++++++++++++selFoto.erroUploadFoto('Erro+HTTP:+'%2BXMLHttpRequest.statusText);
++++++++++++}
++++++++++++else+if+(XMLHttpRequest.readyState+==+0)+{
+++++++++++++++++//+Network+error+(i.e.+connection+refused,+access+denied+due+to+CORS,+etc.)
+++++++++++++++++selFoto.erroUploadFoto('Erro+de+rede:'%2BXMLHttpRequest.statusText);
++++++++++++}
++++++++++++else+{
++++++++++++++++selFoto.erroUploadFoto('Erro+desconhecido.');
++++++++++++}
++++++++};

++++++++xhr.send(formData);
+++++}
+++++else{
++++++++selFoto.erroUploadFoto('');+++++++++++++++++++++++++
++++++++MyCity.mensagens.push('Selecione+uma+imagem.');
++++++++MyCity.showMensagensAlerta();
+++++}
++},+

++erroUploadFoto+:+function(mensagem)+{
++++++++selFoto.foto+=+null;
++++++++$('#file-upload').val('');
++++++++LoadMod.hide();
++++++++MyCity.mensagens.push('Erro+ao+atualizar+a+foto.+'%2Bmensagem);
++++++++MyCity.showMensagensAlerta();
+}
+};|1192537|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

USE 

<pre><code>xhr.onerror = function(e){
 if (XMLHttpRequest.readyState == 4) {
 // HTTP error (can be checked by XMLHttpRequest.status and XMLHttpRequest.statusText)
 selFoto.erroUploadFoto('Erro HTTP: '+XMLHttpRequest.statusText);
 }
 else if (XMLHttpRequest.readyState == 0) {
 // Network error (i.e. connection refused, access denied due to CORS, etc.)
 selFoto.erroUploadFoto('Erro de rede:'+XMLHttpRequest.statusText);
 }
 else {
 selFoto.erroUploadFoto('Erro desconhecido.');
 }

};
</code></pre>

(more code below - UPLOAD IMAGE EXAMPLE)

<pre><code>var selFoto = {
 foto: null,

 upload: function(){
 LoadMod.show();

 var arquivo = document.frmServico.fileupload.files[0];
 var formData = new FormData();

 if (arquivo.type.match('image.*')) {
 formData.append('upload', arquivo, arquivo.name);

 var xhr = new XMLHttpRequest();
 xhr.open('POST', 'FotoViewServlet?acao=uploadFoto', true);
 xhr.responseType = 'blob';

 xhr.onload = function(e){
 if (this.status == 200) {
 selFoto.foto = this.response;
 var url = window.URL || window.webkitURL;
 document.frmServico.fotoid.src = url.createObjectURL(this.response);
 $('#foto-id').show();
 $('#div_upload_foto').hide(); 
 $('#div_master_upload_foto').css('background-color','transparent');
 $('#div_master_upload_foto').css('border','0');

 Dados.foto = document.frmServico.fotoid;
 LoadMod.hide();
 }
 else{
 erroUploadFoto(XMLHttpRequest.statusText);
 }

 if (XMLHttpRequest.readyState == 4) {
 selFoto.erroUploadFoto('Erro HTTP: '+XMLHttpRequest.statusText);
 }
 else if (XMLHttpRequest.readyState == 0) {
 selFoto.erroUploadFoto('Erro de rede:'+XMLHttpRequest.statusText); 
 }

 };

 xhr.onerror = function(e){
 if (XMLHttpRequest.readyState == 4) {
 // HTTP error (can be checked by XMLHttpRequest.status and XMLHttpRequest.statusText)
 selFoto.erroUploadFoto('Erro HTTP: '+XMLHttpRequest.statusText);
 }
 else if (XMLHttpRequest.readyState == 0) {
 // Network error (i.e. connection refused, access denied due to CORS, etc.)
 selFoto.erroUploadFoto('Erro de rede:'+XMLHttpRequest.statusText);
 }
 else {
 selFoto.erroUploadFoto('Erro desconhecido.');
 }
 };

 xhr.send(formData);
 }
 else{
 selFoto.erroUploadFoto(''); 
 MyCity.mensagens.push('Selecione uma imagem.');
 MyCity.showMensagensAlerta();
 }
 }, 

 erroUploadFoto : function(mensagem) {
 selFoto.foto = null;
 $('#file-upload').val('');
 LoadMod.hide();
 MyCity.mensagens.push('Erro ao atualizar a foto. '+mensagem);
 MyCity.showMensagensAlerta();
 }
 };
</code></pre>

I have some Javascript JQuery code that does an Ajax call to the server every 5 mins, it's to keep the server session alive and keep the user logged in. I'm using <code>$.ajax()</code> method in JQuery. This function seems to have an 'error' property that I'm trying to use in the event that the user's internet connection goes down so that the KeepAlive script continues to run. I'm using the following code:

<pre><code>var keepAliveTimeout = 1000 * 10;

function keepSessionAlive()
{
 $.ajax(
 {
 type: 'GET',
 url: 'http://www.mywebapp.com/keepAlive',
 success: function(data)
 {
 alert('Success');

 setTimeout(function()
 {
 keepSessionAlive();
 }, keepAliveTimeout);
 },
 error: function(XMLHttpRequest, textStatus, errorThrown)
 {
 alert('Failure');

 setTimeout(function()
 {
 keepSessionAlive();
 }, keepAliveTimeout);
 }
 });
}
</code></pre>

When I run it, I'll get 'Success' popup on the screen in an alert box every 10 seconds which is fine. However, as soon as I unplug the network cable, I get nothing, I was expecting the error function to get called and see a 'Failure' alert box, but nothing happens.

Am I correct in assuming that the 'error' function is only for non '200' status codes returned from the server? Is there a way to detect network connection problems when making an Ajax call?

JQuery Ajax - How to Detect Network Connection error when making Ajax call

服务器

jQuery

我有一些Javascript JQuery代码，它每隔5分钟对服务器进行一次Ajax调用，这是为了让服务器会话保持活动状态，并让用户保持登录状态。我在JQuery中使用$.ajax()方法。这个函数似乎有一个'error‘属性，我试图在用户的互联网连接中断的情况下使用它，以便KeepAlive脚本继续运行。我使用了以下...

问JQuery Ajax -如何在进行Ajax调用时检测网络连接错误
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