RexxHTTP examples

Click the links to see the servlet in action, and the arrows to inspect the source code.

Say "Hello, world!"

"Hello, world!" & Unicode

Say "नमस्ते",  "P ≝ 𝔐",  "🦞🍐"

A simple HTML servlet

.response~content_type = 'text/html; charset=utf-8'

Say .resources~HTML

::Resource HTML
<!DOCTYPE html>
<html lang="en">
  <head>
    <title>A 'Hello world!' HTML servlet</title>
  </head>
  <body>
    <p>
       Hello, world!
    </p>
    <p>
      <small><a href="../">⬅️ Back to the examples.</a></small>
    </p>
  </body>
</html>
::END

Servlet showing HTML and Unicode

.response~content_type = 'text/html; charset=utf-8'

Say .resources~HTML

::Resource HTML
<!DOCTYPE html>
<html lang="en">
  <head>
    <title>A 'Hello world!' HTML and Unicode servlet</title>
  </head>
  <body>
    <p>
       Hello, world!
       <br>नमस्ते
       <br>P ≝ 𝔐
       <br>🦞🍐
    </p>
    <p>
      <small><a href="../">⬅️ Back to the examples.</a></small>
    </p>
  </body>
</html>
::END

Reading a GET form with arg

.response~content_type = 'text/html; charset=utf-8'

Say '<!DOCTYPE html>'
Say '<html lang="en">'
Say '  <head>'
Say "    <title>A simple GET-form servlet</title>"
Say '  </head>'
Say '  <body>'

If .request~arg("name", "Exists") Then Do
  name = .request~arg("name")
  If name = "" Then Say '    <p>The name can not be empty.</p>'
  Else Call Greet
End

Call PrintForm

Say '    <p>'
Say '      <small><a href="../">⬅️ Back to the examples.</a></small>'
Say '    </p>'
Say '  </body>'
Say '</html>'
Exit

Greet:
  Say '    <p>Hello, '.response~encodeHTML(name)'!</p>'
Return

PrintForm:
  Say '    <form method="get">'
  Say '      <label>Please enter your name: <input type="text" name="name"></label>'
  Say '      <button type="submit">Say hello</button>'
  Say '    </form>'
Return

Setting and reading a cookie

.response~content_type = 'text/html; charset=utf-8'

remembered = .request~cookie("name")

If .request~arg("forget", "Exists") Then Do
  gone = .HTTP.Cookie~new("name", "")
  gone~path    = "/"
  gone~max_age = 0
  .response~addcookie(gone)
  remembered = ""
End
Else If remembered = "", .request~arg("name", "Exists") Then Do
  name = .request~arg("name")
  If name \= "" Then Do
    c = .HTTP.Cookie~new("name", .response~encodeURIComponent(name))
    c~path = "/"
    .response~addcookie(c)
    remembered = name
  End
End

Say '<!DOCTYPE html>'
Say '<html lang="en">'
Say '  <head>'
Say "    <title>A simple cookie servlet</title>"
Say '  </head>'
Say '  <body>'

If remembered \= "" Then Call Welcome
Else Call PrintForm

Say '    <p>'
Say '      <small><a href="../">⬅️ Back to the examples.</a></small>'
Say '    </p>'
Say '  </body>'
Say '</html>'
Exit

Welcome:
  Say '    <p>Welcome back, '.response~encodeHTML(remembered)'!</p>'
  Say '    <p><small><a href="?forget=1">Forget me</a></small></p>'
Return

PrintForm:
  Say '    <form method="get">'
  Say '      <label>Please enter your name: <input type="text" name="name"></label>'
  Say '      <button type="submit">Remember me</button>'
  Say '    </form>'
Return

Fetching and merging JSON from the web

.response~content_type = 'text/html; charset=utf-8'

Say '<!DOCTYPE html>'
Say '<html lang="en">'
Say '  <head>'
Say "    <title>A simple aggregating servlet</title>"
Say '  </head>'
Say '  <body>'
Say '    <h1>Two posts, fetched and merged</h1>'
Say '    <p>This servlet fetches two sample posts from the public'
Say '       <a href="https://jsonplaceholder.typicode.com/">JSONPlaceholder</a>'
Say '       API, parses their JSON, and shows them below. The placeholder text'
Say '       is theirs &mdash; what this example demonstrates is a servlet reaching'
Say '       out to the network and composing the results.</p>'

Base = "https://jsonplaceholder.typicode.com/posts/"

Do id = 1 To 2
  post = FetchJSON(Base || id)
  If post == .nil Then
    Say '    <p>Could not load post 'id'.</p>'
  Else Do
    Say '    <article>'
    Say '      <h2>#'.response~encodeHTML(post["id"])' &mdash; '.response~encodeHTML(post["title"])'</h2>'
    Say '      <p>'.response~encodeHTML(post["body"])'</p>'
    Say '    </article>'
  End
End

Say '    <p>'
Say '      <small><a href="../">⬅️ Back to the examples.</a></small>'
Say '    </p>'
Say '  </body>'
Say '</html>'
Exit

-- Fetch a URL and parse the JSON body into a Rexx object.
-- Returns .nil if the download fails or the body is not valid JSON.
-- Note: this blocks the CGI process until wget returns, so we keep it
-- on a short leash -- --timeout caps DNS/connect/read at 5s each, and
-- --tries=1 stops wget's default 20 silent retries from hanging the
-- request when the remote host is down.
FetchJSON: Procedure
  Use Strict Arg url

  Address Command "wget -qO- --timeout=5 --tries=1" url With Output Stem lines.
  If RC \= 0 Then Return .nil

  text = ""
  Do i = 1 To lines.0
    If i > 1 Then text = text || "0a"x
    text = text || lines.i
  End

  Signal On Syntax Name BadJSON
  Return .json~fromJson(text)

BadJSON:
  Return .nil

::Requires "json.cls"