1.2 Simple Single Servlet Servers

(require web-server/servlet-env)

The Web Server provides a way to quickly configure and start a server instance.

Here’s a simple example:

#lang scheme

(require web-server/servlet

web-server/servlet-env)

(define (my-app request)

`(html (head (title "Hello world!"))

(body (p "Hey out there!"))))

(serve/servlet my-app)

Suppose you’d like to change the port to something else, change the last line to:

(serve/servlet my-app

#:port 8080)

By default the URL for your servlet is "http://localhost:8000/servlets/standalone.ss", suppose you wanted it to be "http://localhost:8000/hello.ss":

(serve/servlet my-app

#:servlet-path "/hello.ss")

Suppose you wanted it to capture top-level requests:

(serve/servlet my-app

#:servlet-path "/")

Or, perhaps just some nice top-level name:

(serve/servlet my-app

#:servlet-path "/main")

Suppose you wanted to use a style-sheet ("style.css") found on your Desktop ("/Users/jay/Desktop/"):

(serve/servlet my-app

#:extra-files-paths

(list

(build-path "/Users/jay/Desktop")))

These files are served in addition to those from the #:server-root-path "htdocs" directory. Notice that you may pass any number of extra paths.

Suppose you would like to start a server for a stateless Web servlet "servlet.ss" that provides start:

#lang scheme

(require "servlet.ss"

web-server/servlet-env)

(serve/servlet start #:stateless? #t)

Note: If you put the call to serve/servlet in the module like normal, strange things will happen because of the way the top-level interacts with continuations. (Read: Don’t do it.)

If you want to use serve/servlet in a start up script for a Web server, and don’t want a browser opened or the DrScheme banner printed, then you can write:

(serve/servlet my-app

#:command-line? #t)

(serve/servlet       start      [ #:command-line? command-line?       #:launch-browser? launch-browser?       #:quit? quit?       #:banner? banner?       #:listen-ip listen-ip       #:port port       #:servlet-path servlet-path       #:servlet-regexp servlet-regexp       #:stateless? stateless?       #:manager manager       #:servlet-namespace servlet-namespace       #:server-root-path server-root-path       #:extra-files-paths extra-files-paths       #:servlets-root servlets-root       #:servlet-current-directory servlet-current-directory]       #:file-not-found-responder file-not-found-responder      [ #:mime-types-path mime-types-path])

→ void

start : (request? . -> . response?)

command-line? : boolean? = #f

launch-browser? : boolean? = (not command-line?)

quit? : boolean? = (not command-line?)

banner? : boolean? = (not command-line?)

listen-ip : string? = "127.0.0.1"

port : number? = 8000

servlet-path : string? = "/servlets/standalone.ss"

servlet-regexp   :   regexp?       =   (regexp (format "^~a$" (regexp-quote servlet-path)))

stateless? : boolean? = #f

manager   :   manager?       =   (make-threshold-LRU-manager #f (* 1024 1024 64))

servlet-namespace : (listof module-path?) = empty

server-root-path : path? = default-server-root-path

extra-files-paths   :   (listof path?)       =   (list (build-path server-root-path "htdocs"))

servlets-root : path? = (build-path server-root-path "htdocs")

servlet-current-directory : path? = servlets-root

file-not-found-responder : (gen-file-not-found-responder (build-path server-root-path "conf" "not-found.html"))

mime-types-path   :   path?       =   (build-path server-root-path "mime.types")

This sets up and starts a fairly default server instance.

start is loaded as a servlet and responds to requests that match servlet-regexp. The current directory of servlet execution is servlet-current-directory.

If launch-browser? is true, then a web browser is opened to "http://localhost:<port><servlet-path>".

If quit? is true, then the URL "/quit" ends the server.

If stateless? is true, then the servlet is run as a stateless web-server module.

Advanced users may need the following options:

The server listens on listen-ip and port port.

The servlet is loaded with manager as its continuation manager. (The default manager limits the amount of memory to 64 MB and deals with memory pressure as discussed in the make-threshold-LRU-manager documentation.)

The modules specified by servlet-namespace are shared with other servlets.

The server files are rooted at server-root-path (which is defaultly the distribution root.) File paths, in addition to the "htdocs" directory under server-root-path may be provided with extra-files-paths. These paths are checked first, in the order they appear in the list.

Other servlets are served from servlets-root.

If a file cannot be found, file-not-found-responder is used to generate an error response.

If banner? is true, then an informative banner is printed. You may want to use this when running from the command line, in which case the command-line? option controls similar options.

MIME types are looked up at mime-types-path.