Is Safari on iOS 6 caching ajax results

Question

Since the upgrade to iOS 6  we are seeing Safari s web view take the liberty of caching   ajax calls  This is in the context of a PhoneGap application so it is using the Safari WebView  Our   ajax calls are POST methods and we have cache set to false  cache false   but still this is happening  We tried manually adding a TimeStamp to the headers but it did not help   We did more research and found that Safari is only returning cached results for web services that have a function signature that is static and does not change from call to call   For instance  imagine a function called something like   getNewRecordID intRecordType    This function receives the same input parameters over and over again  but the data it returns should be different every time   Must be in Apple s haste to make iOS 6 zip along impressively they got too happy with the cache settings   Has anyone else seen this behavior on iOS 6  If so  what exactly is causing it     The workaround that we found was to modify the function signature to be something like this   getNewRecordID intRecordType  strTimestamp    and then always pass in a TimeStamp parameter as well  and just discard that value on the server side   This works around the issue   I hope this helps some other poor soul who spends 15 hours on this issue like I did

User · Answer

My workaround in ASP NET  pagemethods  webservice  etc    protected void Application BeginRequest object sender  EventArgs e        Response Cache SetCacheability HttpCacheability NoCache

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I was able to fix my problem by using a combination of   ajaxSetup and appending a timestamp to the url of my post  not to the post parameters body   This based on the recommendations of previous answers    document  ready function          ajaxSetup   type  POST   headers    cache-control   no-cache               myForm   submit function             var data       myForm   serialize            var now   new Date            var n   now getTime              ajax               type   POST               url   myendpoint cfc method login amp time   n              data  data              success  function results                   if results success                        window location    app cfm                     else                       console log results                       alert  login failed

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I just had this issue as well in a PhoneGap application  I solved it by using the JavaScript function getTime   in the following manner   var currentTime   new Date    var n   currentTime getTime    postUrl    http   www example com test php nocache   n    post postUrl  callbackFunction     I wasted a few hours figuring this out  It would have been nice of Apple to notify developers of this caching issue

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You can also fix this issue by modifying the jQuery Ajax function by doing the following  as of 1 7 1  to the top of the Ajax function  function starts at line 7212   This change will activate the built-in anti-cache feature of jQuery for all POST requests    The full script is available at http   dl dropbox com u 58016866 jquery-1 7 1 js    Insert below line 7221   if  options type      POST         options cache   false      Then modify the following  starting at line  7497    if   s hasContent           If data is available  append data to URL     if  s data            s url     rquery test s url      amp            s data              9682  remove data so that it s not used in an eventual retry         delete s data                Get ifModifiedKey before adding the anti-cache parameter     ifModifiedKey   s url          Add anti-cache in URL if needed     if  s cache     false            var ts   jQuery now               Try replacing    if it is there         ret   s url replace rts    1      ts               If nothing was replaced  add timestamp to the end          s url   ret     ret     s url     rquery test s url      amp                   ts                  To      More options handling for requests with no content if   s hasContent           If data is available  append data to URL     if  s data            s url     rquery test s url      amp            s data              9682  remove data so that it s not used in an eventual retry         delete s data                Get ifModifiedKey before adding the anti-cache parameter     ifModifiedKey   s url        Add anti-cache in URL if needed if  s cache     false        var ts   jQuery now           Try replacing    if it is there     ret   s url replace rts    1      ts           If nothing was replaced  add timestamp to the end      s url   ret     ret     s url     rquery test s url      amp                   ts

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It worked with ASP NET only after adding the pragma no-cache header in IIS  Cache-Control  no-cache was not enough

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For those that use Struts 1  here is how I fixed the issue   web xml   lt filter gt       lt filter-name gt SetCacheControl lt  filter-name gt       lt filter-class gt com example struts filters CacheControlFilter lt  filter-class gt   lt  filter gt    lt filter-mapping gt       lt filter-name gt SetCacheControl lt  filter-name gt       lt url-pattern gt   do lt  url-pattern gt       lt http-method gt POST lt  http-method gt   lt  filter-mapping gt    com example struts filters CacheControlFilter js  package com example struts filters   import java io IOException  import java util Date  import javax servlet    import javax servlet http HttpServletResponse   public class CacheControlFilter implements Filter            public void doFilter ServletRequest request  ServletResponse response                       FilterChain chain  throws IOException  ServletException            HttpServletResponse resp    HttpServletResponse  response          resp setHeader  Expires    Mon  18 Jun 1973 18 00 00 GMT            resp setHeader  Last-Modified   new Date   toString             resp setHeader  Cache-Control    no-store  no-cache  must-revalidate  max-age 0  post-check 0  pre-check 0            resp setHeader  Pragma    no-cache             chain doFilter request  response              public void init FilterConfig filterConfig  throws ServletException              public void destroy

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Depending on the app you can trouble shoot the issue now in iOS 6 using Safari Advanced Web Inspector so that is helpful with this situation    Connect the phone to Safari on a Mac an then use the developer menu to trouble shoot the web app    Clear the website data on the iPhone after update to iOS6  including specific to the app using a Web View  Only one app had an issue and this solved it during IOS6 Beta testing way back  since then no real problems    You may need to look at your app as well  check out NSURLCache if in a WebView in a custom app   https   developer apple com library ios  documentation Cocoa Reference Foundation Classes NSURLCache Class Reference Reference html   apple ref doc uid TP40003754  I guess depending on the true nature of your problem  implementation  etc        Ref     ajax calls

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I found one workaround that makes me curious as to why it works   Before reading Tadej s answer concerning ASP NET web service  I was trying to come up with something that would work     And I m not saying that it s a good solution  but I just wanted to document it here   main page   includes a JavaScript function  checkStatus     The method calls another method which uses a jQuery AJAX call to update the html content   I used setInterval to call checkStatus     Of course  I ran into the caching problem   Solution   use another page to call the update   On the main page  I set a boolean variable  runUpdate  and added the following to the body tag    lt iframe src  helper html  style  display  none  visibility  hidden   gt  lt  iframe gt    In the  of helper html    lt meta http-equiv  refresh  content  5  gt   lt script type  text javascript  gt      if  parent runUpdate    parent checkStatus       lt  script gt    So  if checkStatus   is called from the main page  I get the cached content   If I call checkStatus from the child page  I get updated content

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We found that older iPhones and iPads  running iOS versions 9  amp  10  occasionally return bogus blank AJAX results  perhaps due to Apple s turning down CPU speed  When returning the blank result  iOS does not call the server  as if returning a result from cache  Frequency varies widely  from roughly 10  to 30  of AJAX calls return blank   The solution is hard to believe  Just wait 1s and call again  In our testing  only one repeat was all that was ever needed  but we wrote the code to call up to 4 times  We re not sure if the 1s wait is required  but we didn t want to risk burdening our server with bursts of repeated calls   We found the problem happened with two different AJAX calls  calling on different API files with different data  But I m concerned it could happen on any AJAX call  We just don t know because we don t inspect every AJAX result and we don t test every call multiple times on old devices   Both problem AJAX calls were using  POST  Asynchronously   true  setRequestHeader     Content-Type    application x-www-form-urlencoded    When the problem happens  there s usually only one AJAX call going on  So it s not due to overlapping AJAX calls  Sometimes the problem happens when the device is busy  but sometimes not  and without DevTools we don t really know what s happening at the time   iOS 13 doesn t do this  nor Chrome or Firefox  We don t have any test devices running iOS 11 or 12  Perhaps someone else could test those   I m noting this here because this question is the top Google result when searching for this problem

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That s the work around for GWT-RPC  class AuthenticatingRequestBuilder extends RpcRequestBuilder            Override        protected RequestBuilder doCreate String serviceEntryPoint                           RequestBuilder requestBuilder   super doCreate serviceEntryPoint                             requestBuilder setHeader  Cache-Control    no-cache                    return requestBuilder              AuthenticatingRequestBuilder builder   new AuthenticatingRequestBuilder      ServiceDefTarget myService  setRpcRequestBuilder builder

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I think you have already resolved your issue  but let me share an idea about web caching   It is true you can add many headers in each language you use  server side  client side  and you can use many other tricks to avoid web caching  but always think that you can never know from where the client are connecting to your server  you never know if he are using a Hotel    Hot-Spot    connection that uses Squid or other caching products   If the users are using proxy to hide his real position  etc    the real only way to avoid caching is the timestamp in the request also if is unused   For example    ajax helper php ts 3211321456   Then every cache manager you have to pass didnt find the same URL in the cache repository and go re-download the page content

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While adding cache-buster parameters to make the request look different seems like a solid solution  I would advise against it  as it would hurt any application that relies on actual caching taking place  Making the APIs output the correct headers is the best possible solution  even if that s slightly more difficult than adding cache busters to the callers

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In order to resolve this issue for WebApps added to the home screen  both of the top voted workarounds need to be followed  Caching needs to be turned off on the webserver to prevent new requests from being cached going forward and some random input needs to be added to every post request in order for requests that have already been cached to go through  Please refer to my post   iOS6 - Is there a way to clear cached ajax POST requests for webapp added to home screen   WARNING  to anyone who implemented a workaround by adding a timestamp to their requests without turning off caching on the server  If your app is added to the home screen  EVERY post response will now be cached  clearing safari cache doesn t clear it and it doesn t seem to expire  Unless someone has a way to clear it  this looks like a potential memory leak

User · Answer

A quick work-around for GWT-RPC services is to add this to all the remote methods   getThreadLocalResponse   setHeader  Cache-Control    no-cache

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I hope this can be of use to other developers banging their head against the wall on this one   I found that any of the following prevents Safari on iOS 6 from caching the POST response    adding  cache-control  no-cache  in the request headers adding a variable URL parameter such as the current time adding  pragma  no-cache  in the response headers adding  cache-control  no-cache  in the response headers   My solution was the following in my Javascript  all my AJAX requests are POST      ajaxSetup       type   POST       headers     cache-control    no-cache          I also add the  pragma  no-cache  header to many of my server responses   If you use the above solution be aware that any   ajax   calls you make that are set to global  false will NOT use the settings specified in   ajaxSetup    so you will need to add the headers in again

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Things that DID NOT WORK for me with an iPad 4 iOS 6   My request containing  Cache-Control no-cache    asp net s  HttpContext Current Response Cache SetCacheability HttpCacheability NoCache    Adding cache  false to my jQuery ajax call     ajax                        url  postUrl              type   POST               cache  false                    Only this did the trick   var currentTime   new Date    var n   currentTime getTime    postUrl    http   www example com test php nocache   n    post postUrl  callbackFunction

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I suggest a workaround to modify the function signature to be something like this   getNewRecordID intRecordType  strTimestamp  and then always pass in a TimeStamp parameter as well  and just discard that value on the server side  This works around the issue

User · Answer

Finally  I ve a solution to my uploading problem   In JavaScript   var xhr   new XMLHttpRequest    xhr open  post    uploader php   true   xhr setRequestHeader  pragma    no-cache      In PHP   header  cache-control  no-cache

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From my own blog post iOS 6 0 caching Ajax POST requests   How to fix it  There are various methods to prevent caching of requests  The recommended method is adding a no-cache header  This is how it is done   jQuery   Check for iOS 6 0 and set Ajax header like this     ajaxSetup   cache  false       ZeptoJS   Check for iOS 6 0 and set the Ajax header like this     ajax       type   POST       headers      cache-control    no-cache         url         data       dataType    json       success   function responseText          Server side  Java   httpResponse setHeader  Cache-Control    no-cache  no-store  must-revalidate      Make sure to add this at the top the page before any data is sent to the client    NET  Response Cache SetNoStore      Or  Response Cache SetCacheability System Web HttpCacheability NoCache     PHP  header  Cache-Control  no-cache  no-store  must-revalidate       HTTP 1 1  header  Pragma  no-cache       HTTP 1 0

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Simple solution for all your web service requests  assuming you re using jQuery     ajaxPrefilter function  options  originalOptions  jqXHR           you can use originalOptions type    options type to restrict specific type of requests     options data   jQuery param   extend originalOptions data               timeStamp  new Date   getTime                  Read more about the jQuery prefilter call here   If you aren t using jQuery  check the docs for your library of choice   They may have similar functionality

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After a bit of investigation  turns out that Safari on iOS6 will cache POSTs that have either no Cache-Control headers or even  Cache-Control  max-age 0    The only way I ve found of preventing this caching from happening at a global level rather than having to hack random querystrings onto the end of service calls is to set  Cache-Control  no-cache    So    No Cache-Control or Expires headers   iOS6 Safari will cache Cache-Control max-age 0 and an immediate Expires   iOS6 Safari will cache Cache-Control  no-cache   iOS6 Safari will NOT cache   I suspect that Apple is taking advantage of this from the HTTP spec in section 9 5 about POST      Responses to this method are not cacheable  unless the response      includes appropriate Cache-Control or Expires header fields  However       the 303  See Other  response can be used to direct the user agent to      retrieve a cacheable resource    So in theory you can cache POST responses   who knew  But no other browser maker has ever thought it would be a good idea until now  But that does NOT account for the caching when no Cache-Control or Expires headers are set  only when there are some set  So it must be a bug   Below is what I use in the right bit of my Apache config to target the whole of my API because as it happens I don t actually want to cache anything  even gets  What I don t know is how to set this just for POSTs   Header set Cache-Control  no-cache    Update  Just noticed that I didn t point out that it is only when the POST is the same  so change any of the POST data or URL and you re fine  So you can as mentioned elsewhere just add some random data to the URL or a bit of POST data   Update  You can limit the  no-cache  just to POSTs if you wish like this in Apache   SetEnvIf Request Method  POST  IS POST Header set Cache-Control  no-cache  env IS POST

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This is an update of Baz1nga s answer  Since options data is not an object but a string I just resorted to concatenating the timestamp     ajaxPrefilter function  options  originalOptions  jqXHR      if  originalOptions type     post     options type     post          if  options data  amp  amp  options data length        options data      amp        else       options data            options data     timeStamp     new Date   getTime

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While my login and signup pages works like a charm in Firefox  IE and Chrome    I ve been struggling with this issue in Safari for IOS and OSX  few months ago I found a workaround on the SO    lt body onunload    gt    OR via javascript   lt script type  text javascript  gt  window onunload   function e       e preventDefault        return      lt  script gt       This is kinda ugly thing but works for a while   I don t know why  but returning null to the onunload event the page do not get cached in Safari

User · Answer

This JavaScript snippet works great with jQuery and jQuery Mobile     ajaxSetup       cache  false      headers             Cache-Control    no-cache              Just place it somewhere in your JavaScript code  after jQuery is loaded  and best before you do AJAX requests  and it should help

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I had the same problem with a webapp getting data from ASP NET webservice  This worked for me   public WebService         HttpContext Current Response Cache SetCacheability HttpCacheability NoCache

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