Redirect in AsyncWebServer does not reload the actual page

[Mark81]

In my ESP32 application I use the AsyncWebServer library.
I have an index.html page where I show a table dinamically built at run-time, example:

<div>
    <table id="tableEvents" class="table">
        <thead>
            <tr>
                <th scope="col" width="20px">Id</th>
                <!-- other column headers -->
            </tr>
        </thead>
        <tbody>
            ~TABLE_EVENTS~
        </tbody>
    </table>
</div>

and in my code the preprocessor call this function for `~TABLE_EVENTS~:

String WebApp::tableEvents()
{
  String html = "";

  for (int i = 0; i < _events.Count(); i++)
  {
    Event *e = _events.List()->get(i);
    if (e == nullptr)  continue;

    html += "<tr>";
    html += "<td>" + String(e->id) + "</td>";
    // other fields
    html += "</tr>\n";
  }

  return html;
}

Then I have another html page with a form to submit a new event (that will be added to the table). In the request handler I have the following code:

  _server.on("/event.html", HTTP_POST, [this](AsyncWebServerRequest *request)
  {
    Event *event = new Event();

    int id = -1;
    if (request->hasParam("id")) id = request->getParam("id")->value().toInt();
    // handling of other fields

    addEvent(event, id); // add the event to the list above
    request->redirect(F("/")); // redirect to index.html
  });

My default server configuration is:

  _server.serveStatic("/", LittleFS, "/www")
      .setDefaultFile("index.html")
      .setTemplateProcessor(std::bind(&WebApp::processor, this, std::placeholders::_1));

When I submit the form from event.html it adds a new item to the list and it redirects to index.html. The problem is I don't see the new content. It still shows the old page (without the new item). Even if I refresh the browser (hitting F5) it does change nothing.

The only way I found is to force the whole reload of the page (CTRL+F5), but of course I cannot ask the users to do that each time!

I tried it with different browsers: Chrome, Firefox and Brave and all have the same behavior, so I'm pretty sure I need to change something in my code.

What I need to set in my code to tell the browser to reload the page and not rely on its cache?

I tried to add:

 <meta http-equiv="Cache-Control" content="no-cache, no-store, must-revalidate">
 <meta http-equiv="Pragma" content="no-cache">
 <meta http-equiv="Expires" content="0">

In index.html with no luck.

[AresXT]

@Mark81

tableEvents

where are you using this

[Mark81]

In the preprocessor:

String WebApp::processor(const String &var)
{
    if (var == F("TABLE_EVENTS")) return tableEvents();
}

[Mark81]

Found the solution, I had to add:

DefaultHeaders::Instance().addHeader("Cache-Control", "no-cache, no-store, must-revalidate");
DefaultHeaders::Instance().addHeader("Pragma", "no-cache");
DefaultHeaders::Instance().addHeader("Expires", "0");

before the _server.begin(); line.

[AresXT]

@Mark81

_server.serveStatic

Thats the issue with this .it previous webpages using cached memory .Instead of loading it from device

[AresXT]

You can also use ajax to update the content over static

[Mark81]

I already use Ajax for some features, but it's not always the best solution.

[Mark81]

Are there any other possibilities besides my solution using serveStatic()?

[AresXT]

have you tried websockets..

[AresXT]

using serverstatic() is good rather than implementing each webpage a server.on() if you have few pages you can use server.on it will load directly from server rather than cached version of webpage

[Mark81]

Sorry, I didn't explained it well. I'm not looking for alternative methods for communicate between client and server. I just need to avoid the browser to use its cache when I use serveStatic().

My solution works and it uses header server-side. But since you said:

Thats the issue with this .it previous webpages using cached memory .Instead of loading it from device

I understood there was a settings in the code (like settings the headers) to overcome this.
No problem otherwise, it works now

---

Thanks, now it's clear from your last message!