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55 lines
1.9 KiB
Markdown
55 lines
1.9 KiB
Markdown
---
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title: "S09. Add Pre-Processing to All Routes"
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order: 28
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status: "draft"
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---
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Sometimes you want the same logic to run before every request — auth checks, logging, rate limiting. Register those with `set_pre_routing_handler()`.
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## Basic usage
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```cpp
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svr.set_pre_routing_handler(
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[](const httplib::Request &req, httplib::Response &res) {
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std::cout << req.method << " " << req.path << std::endl;
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return httplib::Server::HandlerResponse::Unhandled;
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});
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```
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The pre-routing handler runs **before routing**. It catches every request — including ones that don't match any handler.
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The `HandlerResponse` return value is key:
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- Return `Unhandled` → continue normally (routing and the actual handler run)
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- Return `Handled` → the response is considered complete, skip the rest
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## Use it for authentication
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Put your shared auth check in one place.
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```cpp
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svr.set_pre_routing_handler(
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[](const httplib::Request &req, httplib::Response &res) {
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if (req.path.rfind("/public", 0) == 0) {
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return httplib::Server::HandlerResponse::Unhandled; // no auth needed
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}
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auto auth = req.get_header_value("Authorization");
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if (auth.empty()) {
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res.status = 401;
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res.set_content("unauthorized", "text/plain");
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return httplib::Server::HandlerResponse::Handled;
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}
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return httplib::Server::HandlerResponse::Unhandled;
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});
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```
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If auth fails, return `Handled` to respond with 401 immediately. If it passes, return `Unhandled` and let routing take over.
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## For per-route auth
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If you want different auth rules per route rather than a single global check, `set_pre_request_handler()` is a better fit. See [S11. Authenticate per route with a pre-request handler](s11-pre-request).
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> **Note:** If all you want is to modify the response, `set_post_routing_handler()` is the right tool. See [S10. Add response headers with a post-routing handler](s10-post-routing).
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