Conceitos

# server.py
from flask import Flask, request, make_response
import uuid
import time

app = Flask(__name__)

ONE_YEAR_SECONDS = 365 * 24 * 60 * 60

@app.before_request
def set_visitor_cookie():
    visitor_id = request.cookies.get("visitor_id")

    if not visitor_id:
        visitor_id = str(uuid.uuid4())

        request.visitor_id = visitor_id
    else:
        request.visitor_id = visitor_id


@app.after_request
def apply_cookie(response):
    if request.cookies.get("visitor_id"):
        return response

    response.set_cookie(
        key="visitor_id",
        value=request.visitor_id,
        max_age=ONE_YEAR_SECONDS,
        httponly=True,
        secure=True,
        samesite="Lax"
    )

    return response


@app.route("/")
def index():
    return make_response("Hello World!")


if __name__ == "__main__":
    app.run(host="0.0.0.0", port=8080)

// main.go
package main

import (
    "log"
    "net/http"
    "time"

    "github.com/google/uuid"
)

const oneYear = 365 * 24 * time.Hour

func visitorMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        _, err := r.Cookie("visitor_id")

        if err == http.ErrNoCookie {
            visitorID := uuid.New().String()

            http.SetCookie(w, &http.Cookie{
                Name:     "visitor_id",
                Value:    visitorID,
                Path:     "/",
                MaxAge:   int(oneYear.Seconds()),
                HttpOnly: true,
                Secure:   true,
                SameSite: http.SameSiteLaxMode,
            })
        }

        next.ServeHTTP(w, r)
    })
}

func main() {
    mux := http.NewServeMux()

    mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        w.Write([]byte("Hello World!"))
    })

    handler := visitorMiddleware(mux)

    log.Println("Server running on port 8080")
    log.Fatal(http.ListenAndServe(":8080", handler))
}

// VisitorCookieFilter.java

import jakarta.servlet.FilterChain;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.Cookie;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.filter.OncePerRequestFilter;

import java.io.IOException;
import java.util.UUID;

@Component
public class VisitorCookieFilter extends OncePerRequestFilter {

    private static final String COOKIE_NAME = "visitor_id";
    private static final int ONE_YEAR_SECONDS = 365 * 24 * 60 * 60;

    @Override
    protected void doFilterInternal(
            HttpServletRequest request,
            HttpServletResponse response,
            FilterChain filterChain
    ) throws ServletException, IOException {

        boolean hasCookie = false;

        if (request.getCookies() != null) {
            for (Cookie cookie : request.getCookies()) {
                if (COOKIE_NAME.equals(cookie.getName())) {
                    hasCookie = true;
                    break;
                }
            }
        }

        if (!hasCookie) {
            String visitorId = UUID.randomUUID().toString();

            Cookie cookie = new Cookie(COOKIE_NAME, visitorId);
            cookie.setPath("/");
            cookie.setHttpOnly(true);
            cookie.setSecure(true);
            cookie.setMaxAge(ONE_YEAR_SECONDS);
            cookie.setAttribute("SameSite", "Lax");

            response.addCookie(cookie);
        }

        filterChain.doFilter(request, response);
    }
}

// HomeController.java

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HomeController {

    @GetMapping("/")
    public String home() {
        return "Hello World!";
    }
}