Router

What is router

Router can route http requests to different handlers. This is a basic and key feature in salvo.

The interior of Router is actually composed of a series of filters (Filter). When a request comes, the route will test itself and its descendants in order to see if they can match the request in the order they were added, and then execute the middleware on the entire chain formed by the route and its descendants in sequence. If the status of Response is set to error (4XX, 5XX) or jump (3XX) during processing, the subsequent middleware and Handler will be skipped. You can also manually adjust ctrl.skip_rest() to skip subsequent middleware and Handler.

Write in flat way

We can write routers in flat way, like this:

Router::with_path("writers").get(list_writers).post(create_writer);
Router::with_path("writers/<id>").get(show_writer).patch(edit_writer).delete(delete_writer);
Router::with_path("writers/<id>/articles").get(list_writer_articles);

Write in tree way

We can write router like a tree, this is also the recommended way:

Router::with_path("writers")
    .get(list_writers)
    .post(create_writer)
    .push(
        Router::with_path("<id>")
            .get(show_writer)
            .patch(edit_writer)
            .delete(delete_writer)
            .push(Router::with_path("articles").get(list_writer_articles)),
    );

This form of definition can make the definition of router clear and simple for complex projects.

There are many methods in Router that will return to Self after being called, so as to write code in a chain. Sometimes, you need to decide how to route according to certain conditions, and the Router also provides then function, which is also easy to use:

Router::new()
    .push(
        Router::with_path("articles")
            .get(list_articles)
            .push(Router::with_path("<id>").get(show_article))
            .then(|router|{
                if admin_mode() {
                    router.post(create_article).push(
                        Router::with_path("<id>").patch(update_article).delete(delete_writer)
                    )
                } else {
                    router
                }
            }),
    );

This example represents that only when the server is in admin_mode, routers such as creating articles, editing and deleting articles will be added.

Get param in routers

In the previous source code, <id> is a param definition. We can access its value via Request instance:

#[handler]
async fn show_writer(req: &mut Request) {
    let id = req.param::<i64>("id").unwrap();
}

<id> matches a fragment in the path, under normal circumstances, the article id is just a number, which we can use regular expressions to restrict id matching rules, r"<id:/\d+/>".

For numeric characters there is an easier way to use <id:num>, the specific writing is:

<id:num>, matches any number of numeric characters;
<id:num[10]>, only matches a certain number of numeric characters, where 10 means that the match only matches 10 numeric characters;
<id:num(..10)> means matching 1 to 9 numeric characters;
<id:num(3..10)> means matching 3 to 9 numeric characters;
<id:num(..=10)> means matching 1 to 10 numeric characters;
<id:num(3..=10)> means match 3 to 10 numeric characters;
<id:num(10..)> means to match at least 10 numeric characters.

You can also use <**>, <*+*> or <*?> to match all remaining path fragments. In order to make the code more readable, you can also add appropriate name to make the path semantics more clear, for example: <**file_path>.

It is allowed to combine multiple expressions to match the same path segment, such as /articles/article_<id:num>/, /images/<name>.<ext>.

Add middlewares

Middleware can be added via hoop method.

Router::new()
    .hoop(check_authed)
    .path("writers")
    .get(list_writers)
    .post(create_writer)
    .push(
        Router::with_path("<id>")
            .get(show_writer)
            .patch(edit_writer)
            .delete(delete_writer)
            .push(Router::with_path("articles").get(list_writer_articles)),
    );

In this example, the root router has a middleware to check current user is authenticated. This middleware will affect the root router and its descendants.

If we don't want to check user is authed when current user view writer informations and articles. We can write router like this:

Router::new()
    .push(
        Router::new()
            .hoop(check_authed)
            .path("writers")
            .post(create_writer)
            .push(Router::with_path("<id>").patch(edit_writer).delete(delete_writer)),
    )
    .push(
        Router::new().path("writers").get(list_writers).push(
            Router::with_path("<id>")
                .get(show_writer)
                .push(Router::with_path("articles").get(list_writer_articles)),
        ),
    );

Although there are two routers have the same path("writers"), they can still be added to the same parent route at the same time.

Filters

Many methods in Router return to themselves in order to easily implement chain writing. Sometimes, in some cases, you need to judge based on conditions before you can add routing. Routing also provides some convenience Method, simplify code writing.

Router uses the filter to determine whether the route matches. The filter supports logical operations and or. Multiple filters can be added to a route. When all the added filters match, the route is matched successfully.

It should be noted that the URL collection of the website is a tree structure, and this structure is not equivalent to the tree structure of Router. A node of the URL may correspond to multiple Router. For example, some paths under the articles/ path require login, and some paths do not require login. Therefore, we can put the same login requirements under a Router, and on top of them Add authentication middleware on Router. In addition, you can access it without logging in and put it under another route without authentication middleware:

Router::new()
    .push(
        Router::new()
            .path("articles")
            .get(list_articles)
            .push(Router::new().path("<id>").get(show_article)),
    )
    .push(
        Router::new()
            .path("articles")
            .hoop(auth_check)
            .post(list_articles)
            .push(Router::new().path("<id>").patch(edit_article).delete(delete_article)),
    );

Router is used to filter requests, and then send the requests to different Handlers for processing.

The most commonly used filtering is path and method. path matches path information; method matches the requested Method.

We can use and, or to connect between filter conditions, for example:

Router::new().filter(filter::path("hello").and(filter::get()));

Path filter

The filter is based on the request path is the most frequently used. Parameters can be defined in the path filter, such as:

Router::with_path("articles/<id>").get(show_article);
Router::with_path("files/<**rest_path>").get(serve_file)

In Handler, it can be obtained through the get_param function of the Request object:

#[handler]
pub async fn show_article(req: &mut Request) {
    let article_id = req.param::<i64>("id");
}

#[handler]
pub async fn serve_file(req: &mut Request) {
    let rest_path = req.param::<i64>("**rest_path");
}

Method filter

Filter requests based on the HTTP request's Method, for example:

Router::new().get(show_article).patch(update_article).delete(delete_article);

Here get, patch, delete are all Method filters. It is actually equivalent to:

use salvo::routing::filter;

let show_router = Router::with_filter(filter::get()).handle(show_article);
let update_router = Router::with_filter(filter::patch()).handle(update_article);
let delete_router = Router::with_filter(filter::get()).handle(delete_article);
Router::new().push(show_router).push(update_router).push(delete_router);

Custom Wisp

For some frequently-occurring matching expressions, we can name a short name by PathFilter::register_wisp_regex or PathFilter::register_wisp_builder. For example, GUID format is often used in paths appears, normally written like this every time a match is required:

Router::with_path("/articles/<id:/[0-9a-fA-F]{8}-([0-9a-fA-F]{4}-){3}[0-9a-fA-F]{12}/>");
Router::with_path("/users/<id:/[0-9a-fA-F]{8}-([0-9a-fA-F]{4}-){3}[0-9a-fA-F]{12}/>");

However, writing this complex regular expression every time is prone to errors and hard-coding the regex is not ideal. We could separate the regex into its own Regex variable like so:

use salvo::routing::filter::PathFilter;

#[tokio::main]
async fn main() {
    let guid = regex::Regex::new("[0-9a-fA-F]{8}-([0-9a-fA-F]{4}-){3}[0-9a-fA-F]{12}").unwrap();
    PathFilter::register_wisp_regex("guid", guid);
    Router::new()
        .push(Router::with_path("/articles/<id:guid>").get(show_article))
        .push(Router::with_path("/users/<id:guid>").get(show_user));
}

You only need to register once, and then you can directly match the GUID through the simple writing method as <id:guid>, which simplifies the writing of the code.

# Router

# What is router

# Write in flat way

# Write in tree way

# Get param in routers

# Add middlewares

# Filters

# Path filter

# Method filter

# Custom Wisp