add minijinja templating example

templating/minijinja/Cargo.toml

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+[package]
+name = "templating-minijinja"
+version = "1.0.0"
+edition = "2021"
+
+[dependencies]
+actix-web = "4"
+actix-web-lab = "0.18"
+
+env_logger = "0.9"
+log = "0.4"
+minijinja = { version = "0.23", features = ["source"] }

templating/minijinja/README.md

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+# MiniJinja
+
+Minimal example of using the template engine [MiniJinja](https://github.com/Keats/tera) that displays a form.
+
+## Usage
+
+```sh
+cd templating/minijinja
+cargo run
+```
+
+- <http://localhost:8080>
+- <http://localhost:8080/non-existing-page> - 404 page rendered using template

templating/minijinja/src/main.rs

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+use std::collections::HashMap;
+
+use actix_web::{
+    dev::ServiceResponse,
+    error,
+    http::{header::ContentType, StatusCode},
+    middleware::{ErrorHandlerResponse, ErrorHandlers, Logger},
+    web, App, Error, HttpResponse, HttpServer, Responder, Result,
+};
+use actix_web_lab::respond::Html;
+
+/// store tera template in application state
+async fn index(
+    tmpl_env: web::Data<minijinja::Environment<'static>>,
+    query: web::Query<HashMap<String, String>>,
+) -> Result<impl Responder, Error> {
+    let html = if let Some(name) = query.get("name") {
+        let tmpl = tmpl_env
+            .get_template("user.html")
+            .map_err(|_| error::ErrorInternalServerError("Template error"))?;
+
+        let ctx = minijinja::context! {
+            name,
+            text => "Welcome!",
+        };
+
+        tmpl.render(ctx)
+            .map_err(|_| error::ErrorInternalServerError("Template error"))?
+    } else {
+        tmpl_env
+            .get_template("index.html")
+            .map_err(|_| error::ErrorInternalServerError("Template error"))?
+            .render(())
+            .map_err(|_| error::ErrorInternalServerError("Template error"))?
+    };
+
+    Ok(Html(html))
+}
+
+#[actix_web::main]
+async fn main() -> std::io::Result<()> {
+    env_logger::init_from_env(env_logger::Env::new().default_filter_or("info"));
+
+    log::info!("starting HTTP server at http://localhost:8080");
+
+    let mut env: minijinja::Environment<'static> = minijinja::Environment::new();
+    env.set_source(minijinja::Source::from_path(concat!(
+        env!("CARGO_MANIFEST_DIR"),
+        "/templates"
+    )));
+
+    HttpServer::new(move || {
+        App::new()
+            .app_data(web::Data::new(env.clone()))
+            .service(web::resource("/").route(web::get().to(index)))
+            .wrap(ErrorHandlers::new().handler(StatusCode::NOT_FOUND, not_found))
+            .wrap(Logger::default())
+    })
+    .workers(2)
+    .bind(("127.0.0.1", 8080))?
+    .run()
+    .await
+}
+
+/// Error handler for a 404 Page not found error.
+fn not_found<B>(svc_res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> {
+    let res = get_error_response(&svc_res, "Page not found");
+
+    Ok(ErrorHandlerResponse::Response(ServiceResponse::new(
+        svc_res.into_parts().0,
+        res.map_into_right_body(),
+    )))
+}
+
+/// Generic error handler.
+fn get_error_response<B>(res: &ServiceResponse<B>, error: &str) -> HttpResponse {
+    let req = res.request();
+
+    // Provide a fallback to a simple plain text response in case an error occurs during the
+    // rendering of the error page.
+    let fallback = |err: &str| {
+        HttpResponse::build(res.status())
+            .content_type(ContentType::plaintext())
+            .body(err.to_string())
+    };
+
+    let ctx = minijinja::context! {
+        error => error,
+        status_code => res.status().as_str(),
+    };
+
+    match req
+        .app_data::<web::Data<minijinja::Environment>>()
+        .and_then(|tmpl_env| tmpl_env.get_template("error.html").ok())
+        .and_then(|tmpl| tmpl.render(ctx).ok())
+    {
+        Some(body) => Html(body)
+            .customize()
+            .with_status(res.status())
+            .respond_to(&req)
+            .map_into_boxed_body(),
+
+        None => fallback(error),
+    }
+}

templating/minijinja/templates/error.html

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+<!DOCTYPE html>
+<html>
+<head>
+  <meta charset="utf-8" />
+  <title>{{ error }}</title>
+</head>
+<body>
+  <h1>{{ status_code }} {{ error }}</h1>
+</body>
+</html>

templating/minijinja/templates/index.html

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+<!DOCTYPE html>
+<html>
+<head>
+  <meta charset="utf-8" />
+  <title>Actix Web</title>
+</head>
+<body>
+  <h1>Welcome!</h1>
+  <p>
+    <h3>What is your name?</h3>
+    <form>
+      <input type="text" name="name" /><br/>
+      <p><input type="submit"></p>
+    </form>
+  </p>
+</body>
+</html>

templating/minijinja/templates/user.html

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+<!DOCTYPE html>
+<html>
+<head>
+  <meta charset="utf-8" />
+  <title>Actix Web</title>
+</head>
+<body>
+  <h1>Hi, {{ name }}!</h1>
+  <p>
+    {{ text }}
+  </p>
+</body>
+</html>