yhirose
9bfd2ddf1c
Bring the READMEs and the docs pages (en and ja) in line with the current header: - Fix the client sample that does not compile, the Transfer-Encoding statement for default headers, the verifier callback comment, the thread pool spawn rule, the sanitize_filename description, and the inverted Accept-Encoding sentence. - Describe recent behaviour: TLS errors behind Read/Write failures, Host validation, Connection: close for a body without length, content_reader rules, refused CONNECT, WebSocketClient proxies, CPPHTTPLIB_INTERIM_RESPONSE_MAX_COUNT, the SSE event size limit, and the payload limit of the Stream API. - Complete the API references of WebSocket, WebSocketClient and the stream:: helpers, and the SSE reconnect rules. - Fix cookbook pages: keychain loading on every backend, received Close status, a multipart sample that trusted the client's file name, an echo sample that sent binary as text, SNI, pre-request handler scope, stop() with WebSocket handlers, and the thread pool notes. - Restore the mutex in the LLM app's Chapter 5 code.
2.0 KiB
title, order, status
| title | order | status |
|---|---|---|
| S03. Use Path Parameters | 22 | draft |
For dynamic URLs like /users/:id — the staple of REST APIs — just put :name in the path pattern. The matched values end up in req.path_params.
Basic usage
svr.Get("/users/:id", [](const httplib::Request &req, httplib::Response &res) {
auto id = req.path_params.at("id");
res.set_content("user id: " + id, "text/plain");
});
A request to /users/42 fills req.path_params["id"] with "42". path_params is a std::unordered_map<std::string, std::string>, so use at() to read it.
Multiple parameters
You can have as many as you need.
svr.Get("/orgs/:org/repos/:repo", [](const httplib::Request &req, httplib::Response &res) {
auto org = req.path_params.at("org");
auto repo = req.path_params.at("repo");
res.set_content(org + "/" + repo, "text/plain");
});
This matches paths like /orgs/anthropic/repos/cpp-httplib.
Regex patterns
For more flexible matching, use a std::regex-based pattern.
svr.Get(R"(/users/(\d+))", [](const httplib::Request &req, httplib::Response &res) {
auto id = req.matches[1];
res.set_content("user id: " + std::string(id), "text/plain");
});
Parentheses in the pattern become captures in req.matches. req.matches[0] is the full match; req.matches[1] onward are the captures.
A regex route isn't applied to a path longer than CPPHTTPLIB_REGEX_ROUTE_PATH_MAX_LENGTH (256 by default); such a path is treated as no match. This keeps std::regex from overflowing the stack on long input. If your routes need longer paths, define the macro with a larger value.
Which to use
- For plain IDs or slugs,
:nameis enough — readable, and the shape is obvious - Use regex when you want to constrain the URL to, say, numbers only or a UUID format
- Mixing both can get confusing — stick with one style per project
Note: Path parameters come in as strings. If you need an integer, convert with
std::stoi()and don't forget to handle conversion errors.