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vweb: add parameter arrays documentation (#18903 )

2023-07-20 02:28:11 +03:00

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vweb - the V Web Server

A simple yet powerful web server with built-in routing, parameter handling, templating, and other features. The gitly site is based on vweb.

Some features may not be complete, and have some bugs.

Quick Start

Just run v new <name> web in your terminal.

Run your vweb app with a live reload via v -d vweb_livereload watch run .

Now modifying any file in your web app (whether it's a .v file with the backend logic or a compiled .html template file) will result in an instant refresh of your app in the browser. No need to quit the app, rebuild it, and refresh the page in the browser!

Features

Very fast performance of C on the web.
Small binary hello world website is <100 KB.
Easy to deploy just one binary file that also includes all templates. No need to install any dependencies.
Templates are precompiled all errors are visible at compilation time, not at runtime.
Multithreaded by default

Examples

There are some examples that can be explored here.

And others like:

vweb_orm_jwt (back-end)
vorum (front-end)
gitly (full-stack)

Front-end getting start example src/main.v

module main

import vweb
import os

struct App {
	vweb.Context
}

struct Object {
	title       string
	description string
}

fn main() {
	vweb.run_at(new_app(), vweb.RunParams{
		port: 8081
	}) or { panic(err) }
}

fn new_app() &App {
	mut app := &App{}
	// makes all static files available.
	app.mount_static_folder_at(os.resource_abs_path('.'), '/')
	return app
}

['/']
pub fn (mut app App) page_home() vweb.Result {
	// all this constants can be accessed by src/templates/page/home.html file.
	page_title := 'V is the new V'
	v_url := 'https://github.com/vlang/v'

	list_of_object := [
		Object{
			title: 'One good title'
			description: 'this is the first'
		},
		Object{
			title: 'Other good title'
			description: 'more one'
		},
	]
	// $vweb.html() in `<folder>_<name> vweb.Result ()` like this
	// render the `<name>.html` in folder `./templates/<folder>`
	return $vweb.html()
}

$vweb.html() compiles an HTML template into V during compilation, and embeds the resulting code into the current action.

That means that the template automatically has access to that action's entire environment.

src/templates/page/home.html

<html>
  <head>
    <title>${page_title}</title>
    @css 'src/templates/page/home.css'
  </head>
  <body>
    <h1 class="title">Hello, Vs.</h1>
    @for var in list_of_object
    <div>
      <a href="${v_url}">${var.title}</a>
      <span>${var.description}</span>
    </div>
    @end
    <div>@include 'component.html'</div>
  </body>
</html>

src/templates/page/component.html

<div>This is a component</div>

src/templates/page/home.css

h1.title {
  font-family: Arial, Helvetica, sans-serif;
  color: #3b7bbf;
}

V supports Template directives like @css, @js for static files in <path> @if, @for for conditional and loop and @include to include html components.

Deploying vweb apps

Everything, including HTML templates, is in one binary file. That's all you need to deploy.

Getting Started

To start with vweb, you have to import the module vweb and define a struct to hold vweb.Context (and any other variables your program will need). The web server can be started by calling vweb.run(&App{}, port) or vweb.run(&App{}, RunParams)

Example:

import vweb

struct App {
    vweb.Context
}

fn main() {
	vweb.run(&App{}, 8080)
	// // or
	// vweb.run_at(new_app(), vweb.RunParams{
	// 	host: 'localhost'
	// 	port: 8099
	// 	family: .ip
	// }) or { panic(err) }
}

Defining endpoints

To add endpoints to your web server, you have to extend the App struct. For routing you can either use auto-mapping of function names or specify the path as an attribute. The function expects a response of the type vweb.Result.

Example:

// This endpoint can be accessed via http://localhost:port/hello
fn (mut app App) hello() vweb.Result {
	return app.text('Hello')
}

// This endpoint can be accessed via http://localhost:port/foo
["/foo"]
fn (mut app App) world() vweb.Result {
	return app.text('World')
}

- HTTP verbs

To use any HTTP verbs (or methods, as they are properly called), such as [post], [get], [put], [patch] or [delete] you can simply add the attribute before the function definition.

Example:

[post]
fn (mut app App) world() vweb.Result {
	return app.text('World')
}

['/product/create'; post]
fn (mut app App) create_product() vweb.Result {
	return app.text('product')
}

- Parameters

Parameters are passed directly in endpoint route using colon sign : and received using the same name at function To pass a parameter to an endpoint, you simply define it inside an attribute, e. g. ['/hello/:user]. After it is defined in the attribute, you have to add it as a function parameter.

Example:

          vvvv
['/hello/:user']            vvvv
fn (mut app App) hello_user(user string) vweb.Result {
	return app.text('Hello $user')
}

You have access to the raw request data such as headers or the request body by accessing app (which is vweb.Context). If you want to read the request body, you can do that by calling app.req.data. To read the request headers, you just call app.req.header and access the header you want example. app.req.header.get(.content_type). See struct Header for all available methods (v doc net.http Header). It has, too, fields for the query, form, files.

- Parameter Arrays

If you want multiple parameters in your route and if you want to parse the parameters yourself, or you want a wildcard route, you can add ... after the : and name, e.g. ['/:path...'].

This will match all routes after '/'. For example the url /path/to/test would give path = '/path/to/test'.

        vvv
['/:path...']             vvvv
fn (mut app App) wildcard(path string) vweb.Result {
	return app.text('URL path = "${path}"')
}

- Query

To handle the query context, you just need use the query field

Example:

module main

import vweb

struct App {
	vweb.Context
}

fn main() {
	vweb.run(&App{}, 8081)
}

['/user'; get]
pub fn (mut app App) controller_get_user_by_id() vweb.Result {
	// http://localhost:3000/user?q=vpm&order_by=desc => { 'q': 'vpm', 'order_by': 'desc' }
	return app.text(app.query.str())
}

- Host

To restrict an endpoint to a specific host, you can use the host attribute followed by a colon : and the host name. You can test the Host feature locally by adding a host to the "hosts" file of your device.

Example:

['/'; host: 'example.com']
pub fn (mut app App) hello_web() vweb.Result {
	return app.text('Hello World')
}

['/'; host: 'api.example.org']
pub fn (mut app App) hello_api() vweb.Result {
	return app.text('Hello API')
}

// define the handler without a host attribute last if you have conflicting paths.
['/']
pub fn (mut app App) hello_others() vweb.Result {
	return app.text('Hello Others')
}

You can also create a controller to handle all requests from a specific host in one app.

Middleware

Vweb has different kinds of middleware. The before_request() method is always called before every request before any other middleware is processed. You could use it to check user session cookies or to add a header.

Example:

pub fn (mut app App) before_request() {
    app.user_id = app.get_cookie('id') or { '0' }
}

Middleware functions can be passed directly when creating an App instance and is executed when the url starts with the defined key.

In the following example, if a user navigates to /path/to/test the middleware is executed in the following order: middleware_func, other_func, global_middleware. The middleware is executed in the same order as they are defined and if any function in the chain returns false the propogation is stopped.

Example:

module main

import vweb

struct App {
	vweb.Context
	middlewares map[string][]vweb.Middleware
}

fn new_app() &App {
	mut app := &App{
		middlewares: {
			// chaining is allowed, middleware will be evaluated in order
			'/path/to/': [middleware_func, other_func]
			'/':         [global_middleware]
		}
	}

	// do stuff with app
	// ...
	return app
}

fn middleware_func(mut ctx vweb.Context) bool {
	// ...
	return true
}

fn other_func(mut ctx vweb.Context) bool {
	// ...
	return true
}

fn global_middleware(mut ctx vweb.Context) bool {
	// ...
	return true
}

Middleware functions will be of type vweb.Middleware and are not methods of App, so they could also be imported from other modules.

pub type Middleware = fn (mut Context) bool

Middleware can also be added to route specific functions via attributes.

Example:

[middleware: check_auth]
['/admin/data']
pub fn (mut app App) admin() vweb.Result {
	// ...
}

// check_auth is a method of App, so we don't need to pass the context as parameter.
pub fn (mut app App) check_auth () bool {
	// ...
	return true
}

You can only add 1 middleware to a route specific function via attributes.

Middleware evaluation order

The middleware is executed in the following order:

before_request
The middleware in app.middlewares
The middleware in the [middleware] attribute

If any function of step 2 or 3 returns false the middleware functions that would come after it are not executed and the app handler will also not be executed. You can think of it as a chain.

Context values

You can store a value pair in vweb's context. It is especially usefull for passing variables from a middleware function to the route handler.

Example:

module main

import vweb

struct App {
	vweb.Context
	middlewares map[string][]vweb.Middleware
}

pub fn (mut app App) index() vweb.Result {
	// get the user or return HTTP 401
	user := app.get_value[User]('user') or {
		app.set_status(401, '')
		return app.text('HTTP 401: Unauthorized')
	}

	return app.text('welcome ${user.name}')
}

fn main() {
	vweb.run(&App{
		middlewares: {
			'/': [get_session]
		}
	}, 8080)
}

struct User {
	session_id string
	name       string
}

fn get_session(mut ctx vweb.Context) bool {
	// impelement your own logic to get the user
	user := User{
		session_id: '123456'
		name: 'Vweb'
	}

	// set the user
	ctx.set_value('user', user)
	return true
}

When you visit the index page the middleware function get_session will run first This function sets a User value to a key 'user'. We get this key in index and display it to the user if the 'user' key exists.

Changing Context values

By default context values are immutable when retrieved with get_value. If you want to change the value later you have to set it again with set_value.

Example:

fn change_user(mut ctx vweb.Context) bool {
	user := User{
		session_id: '654321'
		name: 'tester'
	}

	// set the user
	ctx.set_value('user', user)
	return true
}

Redirect

Used when you want be redirected to an url

Examples:

pub fn (mut app App) before_request() {
	app.user_id = app.get_cookie('id') or { app.redirect('/') }
}

['/articles'; get]
pub fn (mut app App) articles() vweb.Result {
	if !app.token {
		app.redirect('/login')
	}
	return app.text('patatoes')
}

You can also combine middleware and redirect.

Example:

[middleware: with_auth]
['/admin/secret']
pub fn (mut app App) admin_secret() vweb.Result {
	// this code should never be reached
	return app.text('secret')
}

['/redirect']
pub fn (mut app App) with_auth() bool {
	app.redirect('/auth/login')
	return false
}

Custom not found page

You can implement a not_found route that is called when a request is made and no matching route is found to replace the default HTTP 404 not found page.

Example:

pub fn (mut app App) not_found() vweb.Result {
	app.set_status(404, 'Not Found')
	return app.html('<h1>Page not found</h1>')
}

Databases

The db field in a vweb app is reserved for database connections. The connection is copied to each new request.

Example:

module main

import vweb
import db.sqlite

struct App {
	vweb.Context
mut:
	db sqlite.DB
}

fn main() {
	// create the database connection
	mut db := sqlite.connect('db')!

	vweb.run(&App{
		db: db
	}, 8080)
}

Multithreading

By default, a vweb app is multithreaded, that means that multiple requests can be handled in parallel by using multiple CPU's: a worker pool. You can change the number of workers (maximum allowed threads) by altering the nr_workers option. The default behaviour is to use the maximum number of jobs (cores in most cases).

Example:

fn main() {
	// assign a maximum of 4 workers
	vweb.run_at(&App{}, nr_workers: 4)
}

Database Pool

A single connection database works fine if you run your app with 1 worker, of if you access a file-based database like a sqlite file.

This approach will fail when using a non-file based database connection like a mysql connection to another server somewhere on the internet. Multiple threads would need to access the same connection at the same time.

To resolve this issue, you can use the vweb's built-in database pool. The database pool will keep a number of connections open when the app is started and each worker is assigned its own connection.

Let's look how we can improve our previous example with database pooling and using a postgresql server instead.

Example:

module main

import vweb
import db.pg

struct App {
	vweb.Context
	db_handle vweb.DatabasePool[pg.DB]
mut:
	db pg.DB
}

fn get_database_connection() pg.DB {
	// insert your own credentials
	return pg.connect(user: 'user', password: 'password', dbname: 'database') or { panic(err) }
}

fn main() {
	// create the database pool and pass our `get_database_connection` function as handler
	pool := vweb.database_pool(handler: get_database_connection)

	// no need to set the `db` field
	vweb.run(&App{
		db_handle: pool
	}, 8080)
}

If you don't use the default number of workers (nr_workers) you have to change it to the same number in vweb.run_at as in vweb.database_pool

Extending the App struct with `[vweb_global]`

You can change your App struct however you like, but there are some things you have to keep in mind. Under the hood at each request a new instance of App is constructed, and all fields are re-initialized with their default type values, except for the db field.

This behaviour ensures that each request is treated equally and in the same context, but problems arise when we want to provide more context than just the default vweb.Context.

Let's view the following example where we want to provide a secret token to our app:

module main

import vweb

struct App {
	vweb.Context
	secret string
}

fn main() {
	vweb.run(&App{
		secret: 'my secret'
	}, 8080)
}

fn (mut app App) index() vweb.Result {
	return app.text('My secret is: ${app.secret}')
}

When you visit localhost:8080/ you would expect to see the text "My secret is: my secret", but instead there is only the text "My secret is: ". This is because of the way vweb works. We can override the default behaviour by adding the attribute [vweb_global] to the secret field.

Example:

struct App {
	vweb.Context
	secret string [vweb_global]
}

Now if you visit localhost:8080/ you see the text "My secret is: my secret".

Note

: the value of secret gets initialized with the provided value when creating App. If you would modify secret in one request the value won't be changed in the next request. You can use shared fields for this.

Shared Objects across requests

We saw in the previous section that we can persist data across multiple requests, but what if we want to be able to mutate the data? Since vweb works with threads, we have to use shared fields.

Let's see how we can add a visitor counter to our App.

Example:

module main

import vweb

struct Counter {
pub mut:
	count int
}

struct App {
	vweb.Context
mut:
	counter shared Counter // shared fields can only be structs, arrays or maps.
}

fn main() {
	// initialize the shared object
	shared counter := Counter{
		count: 0
	}

	vweb.run(&App{
		counter: counter
	}, 8080)
}

fn (mut app App) index() vweb.Result {
	mut count := 0
	// lock the counter so we can modify it
	lock app.counter {
		app.counter.count += 1
		count = app.counter.count
	}
	return app.text('Total visitors: ${count}')
}

Drawback of Shared Objects

The drawback of using shared objects is that it affects performance. In the previous example App.counter needs to be locked each time the page is loaded if there are simultaneous requests the next requests will have to wait for the lock to be released.

It is best practice to limit the use of shared objects as much as possible.

Controllers

Controllers can be used to split up app logic so you are able to have one struct per "/". E.g. a struct Admin for urls starting with "/admin" and a struct Foo for urls starting with "/foo"

Example:

module main

import vweb

struct App {
	vweb.Context
	vweb.Controller
}

struct Admin {
	vweb.Context
}

struct Foo {
	vweb.Context
}

fn main() {
	mut app := &App{
		controllers: [
			vweb.controller('/admin', &Admin{}),
			vweb.controller('/foo', &Foo{}),
		]
	}
	vweb.run(app, 8080)
}

You can do everything with a controller struct as with a regular App struct. The only difference being is that only the main app that is being passed to vweb.run is able to have controllers. If you add vweb.Controller on a controller struct it will simply be ignored.

Routing

Any route inside a controller struct is treated as a relative route to its controller namespace.

['/path']
pub fn (mut app Admin) path vweb.Result {
    return app.text('Admin')
}

When we created the controller with vweb.controller('/admin', &Admin{}) we told vweb that the namespace of that controller is "/admin" so in this example we would see the text "Admin" if we navigate to the url "/admin/path".

Vweb doesn't support fallback routes or duplicate routes, so if we add the following route to the example the code will produce an error.

['/admin/path']
pub fn (mut app App) admin_path vweb.Result {
    return app.text('Admin overwrite')
}

There will be an error, because the controller Admin handles all routes starting with "/admin"; the method admin_path is unreachable.

Hosts

You can also set a host for a controller. All requests coming from that host will be handled by the controller.

Example:

module main

import vweb

struct App {
	vweb.Context
	vweb.Controller
}

pub fn (mut app App) index() vweb.Result {
	return app.text('App')
}

struct Example {
	vweb.Context
}

// You can only access this route at example.com: http://example.com/
pub fn (mut app Example) index() vweb.Result {
	return app.text('Example')
}

fn main() {
	vweb.run(&App{
		controllers: [
			vweb.controller_host('example.com', '/', &Example{}),
		]
	}, 8080)
}

Databases and `[vweb_global]` in controllers

Fields with [vweb_global] have to passed to each controller individually. The db field is unique and will be treated as a vweb_global field at all times.

Example:

module main

import vweb
import db.sqlite

struct App {
	vweb.Context
	vweb.Controller
mut:
	db sqlite.DB
}

struct Admin {
	vweb.Context
mut:
	db sqlite.DB
}

fn main() {
	mut db := sqlite.connect('db')!

	mut app := &App{
		db: db
		controllers: [
			vweb.controller('/admin', &Admin{
				db: db
			}),
		]
	}
}

Using a database pool

Example:

module main

import vweb
import db.pg

struct App {
	vweb.Context
	vweb.Controller
	db_handle vweb.DatabasePool[pg.DB]
mut:
	db pg.DB
}

struct Admin {
	vweb.Context
	db_handle vweb.DatabasePool[pg.DB]
mut:
	db pg.DB
}

fn get_database_connection() pg.DB {
	// insert your own credentials
	return pg.connect(user: 'user', password: 'password', dbname: 'database') or { panic(err) }
}

fn main() {
	// create the database pool and pass our `get_database_connection` function as handler
	pool := vweb.database_pool(handler: get_database_connection)

	mut app := &App{
		db_handle: pool
		controllers: [
			vweb.controller('/admin', &Admin{
				db_handle: pool
			}),
		]
	}
}

Responses

- set_status

Sets the response status Example:

['/user/get_all'; get]
pub fn (mut app App) controller_get_all_user() vweb.Result {
    token := app.get_header('token')

    if !token {
        app.set_status(401, '')
        return app.text('Not valid token')
    }

    response := app.service_get_all_user() or {
        app.set_status(400, '')
        return app.text('$err')
    }
    return app.json(response)
}

- html

Response HTTP_OK with payload with content-type text/html Example:

pub fn (mut app App) html_page() vweb.Result {
    return app.html('<h1>ok</h1>')
}

- text

Response HTTP_OK with payload with content-type text/plain Example:

pub fn (mut app App) simple() vweb.Result {
    return app.text('A simple result')
}

- json

Response HTTP_OK with payload with content-type application/json Examples:

['/articles'; get]
pub fn (mut app App) articles() vweb.Result {
    articles := app.find_all_articles()
    json_result := json.encode(articles)
    return app.json(json_result)
}

['/user/create'; post]
pub fn (mut app App) controller_create_user() vweb.Result {
    body := json.decode(User, app.req.data) or {
        app.set_status(400, '')
        return app.text('Failed to decode json, error: $err')
	}

    response := app.service_add_user(body.username, body.password) or {
        app.set_status(400, '')
        return app.text('error: $err')
    }

    return app.json(response)
}

- json_pretty

Response HTTP_OK with a pretty-printed JSON result Example:

fn (mut app App) time_json_pretty() {
    app.json_pretty({
        'time': time.now().format()
    })
}

- file

Response HTTP_OK with file as payload

- ok

Response HTTP_OK with payload Example:

['/form_echo'; post]
pub fn (mut app App) form_echo() vweb.Result {
    app.set_content_type(app.req.header.get(.content_type) or { '' })
    return app.ok(app.form['foo'])
}

- server_error

Response a server error Example:

fn (mut app App) sse() vweb.Result {
    return app.server_error(501)
}

- not_found

Response HTTP_NOT_FOUND with payload Example:

['/:user/:repo/settings']
pub fn (mut app App) user_repo_settings(username string, repository string) vweb.Result {
    if username !in known_users {
        return app.not_found()
    }
    return app.html('username: $username | repository: $repository')
}

Requests

- get_header

Returns the header data from the key Example:

['/user/get_all'; get]
pub fn (mut app App) controller_get_all_user() vweb.Result {
    token := app.get_header('token')
    return app.text(token)
}

- get_cookie

Sets a cookie Example:

pub fn (mut app App) before_request() {
    app.user_id = app.get_cookie('id') or { '0' }
}

- add_header

Adds an header to the response with key and val Example:

['/upload'; post]
pub fn (mut app App) upload() vweb.Result {
    fdata := app.files['upfile']

    data_rows := fdata[0].data.split('\n')

    mut output_data := ''

    for elem in data_rows {
        delim_row := elem.split('\t')
        output_data += '${delim_row[0]}\t${delim_row[1]}\t'
        output_data += '${delim_row[0].int() + delim_row[1].int()}\n'
	}

    output_data = output_data.all_before_last('\n')

    app.add_header('Content-Disposition', 'attachment; filename=results.txt')
    app.send_response_to_client('application/octet-stream', output_data)

    return $vweb.html()
}

- set_cookie

Sets a cookie Example:

pub fn (mut app App) cookie() vweb.Result {
    app.set_cookie(name: 'cookie', value: 'test')
    return app.text('Response Headers\n$app.header')
}

- set_cookie_with_expire_date

Sets a cookie with a expire_data Example:

pub fn (mut app App) cookie() vweb.Result {
    key := 'cookie'
    value := 'test'
    duration := time.Duration(2 * time.minute ) // add 2 minutes
    expire_date := time.now().add(duration)

    app.set_cookie_with_expire_date(key, value, expire_date)
    return app.text('Response Headers\n$app.header')
}

- set_content_type

Sets the response content type Example:

['/form_echo'; post]
pub fn (mut app App) form_echo() vweb.Result {
    app.set_content_type(app.req.header.get(.content_type) or { '' })
    return app.ok(app.form['foo'])
}

Template

-handle_static

handle_static is used to mark a folder (relative to the current working folder) as one that contains only static resources (css files, images etc).
host_handle_static can be used to limit the static resources to a specific host.

If root is set the mount path for the dir will be in '/'

Example:

fn main() {
    mut app := &App{}
    app.serve_static('/favicon.ico', 'favicon.ico')
    // app.host_serve_static('localhost', '/favicon.ico', 'favicon.ico')
    // Automatically make available known static mime types found in given directory.
    os.chdir(os.dir(os.executable()))?
    app.handle_static('assets', true)
    vweb.run(app, port)
}

-mount_static_folder_at

makes all static files in directory_path and inside it, available at http://server/mount_path.

For example: suppose you have called .mount_static_folder_at('/var/share/myassets', '/assets'), and you have a file /var/share/myassets/main.css . => That file will be available at URL: http://server/assets/main.css .

mount_static_folder_at can be used to limit the static resources to a specific host.

-serve_static

Serves a file static. url is the access path on the site, file_path is the real path to the file, mime_type is the file type

host_serve_static can be used to limit the static resources to a specific host.

Example:

fn main() {
    mut app := &App{}
    app.serve_static('/favicon.ico', 'favicon.ico')
    // app.host_serve_static('localhost', /favicon.ico', 'favicon.ico')
    app.mount_static_folder_at(os.resource_abs_path('.'), '/')
    vweb.run(app, 8081)
}

Others

-ip

Returns the ip address from the current user

Example:

pub fn (mut app App) ip() vweb.Result {
    ip := app.ip()
    return app.text('ip: $ip')
}

-error

Set a string to the form error

Example:

pub fn (mut app App) error() vweb.Result {
    app.error('here as an error')
    println(app.form_error) //'vweb error: here as an error'
}

Cross-Site Request Forgery (CSRF) protection

Vweb has built-in csrf protection. Go to the csrf module to learn how you can protect your app against CSRF.

27 KiB Raw Permalink Blame History

vweb - the V Web Server

Quick Start

Features

Examples

Deploying vweb apps

Getting Started

Defining endpoints

- HTTP verbs

- Parameters

- Parameter Arrays

- Query

- Host

Middleware

Middleware evaluation order

Context values

Changing Context values

Redirect

Custom not found page

Databases

Multithreading

Database Pool

Extending the App struct with [vweb_global]

Shared Objects across requests

Drawback of Shared Objects

Controllers

Routing

Hosts

Databases and [vweb_global] in controllers

Using a database pool

Responses

- set_status

- html

- text

- json

- json_pretty

- file

- ok

- server_error

- not_found

Requests

- get_header

- get_cookie

- add_header

- set_cookie

- set_cookie_with_expire_date

- set_content_type

Template

-handle_static

-mount_static_folder_at

-serve_static

Others

-ip

-error

Cross-Site Request Forgery (CSRF) protection

27 KiB

Raw Permalink Blame History

Extending the App struct with `[vweb_global]`

Databases and `[vweb_global]` in controllers