esp8266webserver question: How to run some own code before server.serveStatic();

[chess-levin]

How do I run some own code before server.serveStatic(); ?

I have a html file stored in LittleFS and serve it via httpServer.serveStatic("/action", LittleFS, "/action.html");
Now I want to execute some code first when someone requests /action and then send action.html , but I can't find no other way than to write a handler function that executes my code and then reads the file into a String fileBuffer and finally sending the String via httpServer.send(200, HTML, fileBuffer);

Does anybody has a hint for a better way of doing this?

I'using latest version of esp8266webserver on an wemos d1 mini with 4MB.

[paulocsanz]

You have to create your own handler, it's not hard. You just have to reimplement two places, the boilerplate can get annoying tho.

Implement your custom handler class, like this code:

Arduino/libraries/ESP8266WebServer/src/detail/RequestHandlersImpl.h

Line 213 in 3f4bcbe

class StaticFileRequestHandler

Just copy this entire class and add your logic before the last line of the handle function (the sendStream call).

And set this custom handler class instance to a route like this line:

Arduino/libraries/ESP8266WebServer/src/ESP8266WebServer-impl.h

Line 275 in f401f08

_addRequestHandler(new StaticFileRequestHandler<ServerType>(fs, path, uri, cache_header));

Something like

server.addHandler(new YourStaticFileRequestHandler<WiFiServer>(fs, path, uri, cache_header));

That said, we could add a "file pre-process" callback variable to StaticFileRequestHandler, so the user can build their own handler and set it manually with addHandler

[chess-levin]

My solution was to write a handler function and at the end I'm sending a redirect to to /action.

Thanks for your advice! I'll give it a try! THX

[chess-levin]

Hello @paulocsanz, I've tried to write my own StaticRequestHandler but getting a compiler error. I have no experiences with writing templates in c++. I put this code in a file named ``MyRequestHandler.cppnext to mymain.cpp`.

Could you give me some more hints on how to get this running. Big thank you.

template<typename ServerType>
class MyStaticFileRequestHandler
    :
public StaticRequestHandler<ServerType> {

    using SRH = StaticRequestHandler<ServerType>;
    using WebServerType = ESP8266WebServerTemplate<ServerType>;

public:
    MyStaticFileRequestHandler(FS& fs, const char* path, const char* uri, const char* cache_header)
        :
    StaticRequestHandler<ServerType>{fs, path, uri, cache_header}
    {
    }

    bool canHandle(HTTPMethod requestMethod, const String& requestUri) override  {
        return SRH::validMethod(requestMethod) && requestUri == SRH::_uri;
    }

    bool handle(WebServerType& server, HTTPMethod requestMethod, const String & requestUri) override {
        if (!canHandle(requestMethod, requestUri))
            return false;

        if (server._eTagEnabled) {
            if (server._eTagFunction) {
                _eTagCode = (server._eTagFunction)(SRH::_fs, SRH::_path);
            } else  if (_eTagCode.isEmpty()) {
                _eTagCode = esp8266webserver::calcETag(SRH::_fs, SRH::_path);
            }

            if (server.header("If-None-Match") == _eTagCode) {
                server.send(304);
                return true;
            }
        }

        File f = SRH::_fs.open(SRH::_path, "r");

        if (!f)
            return false;

        if (!f.isFile()) {
            f.close();
            return false;
        }

        if (SRH::_cache_header.length() != 0)
            server.sendHeader("Cache-Control", SRH::_cache_header);

        if ((server._eTagEnabled) && (_eTagCode.length() > 0)) {
            server.sendHeader("ETag", _eTagCode);
        }

        // my code
        // lsPause();

        server.streamFile(f, mime::getContentType(SRH::_path), requestMethod);
        return true;
    }

protected:
    String _eTagCode; // ETag code calculated for this file as used in http header include quotes.
    
};

Compiling .pio\build\esp12e\src\RequestHandler.cpp.o
src\RequestHandler.cpp:4:28: error: expected template-name before '<' token
    4 | public StaticRequestHandler<ServerType> {
      |                            ^
src\RequestHandler.cpp:4:28: error: expected '{' before '<' token
Archiving .pio\build\esp12e\lib186\libESP8266WiFi.a
Archiving .pio\build\esp12e\libcfd\libesp8266_mdns.a
Archiving .pio\build\esp12e\libedf\libWire.a
Archiving .pio\build\esp12e\lib5d5\libBH1750.a
Archiving .pio\build\esp12e\libbfb\libSimpleTimer.a
Compiling .pio\build\esp12e\lib44b\ESP8266WebServer\detail\mimetable.cpp.o
Compiling .pio\build\esp12e\libe74\ESP8266mDNS\ESP8266mDNS.cpp.o
Compiling .pio\build\esp12e\libe74\ESP8266mDNS\LEAmDNS.cpp.o
Compiling .pio\build\esp12e\libe74\ESP8266mDNS\LEAmDNS_Control.cpp.o
Compiling .pio\build\esp12e\libe74\ESP8266mDNS\LEAmDNS_Helpers.cpp.o
*** [.pio\build\esp12e\src\RequestHandler.cpp.o] Error 1
Compiling .pio\build\esp12e\libe74\ESP8266mDNS\LEAmDNS_Structs.cpp.o