251 lines
7.1 KiB
HTML
251 lines
7.1 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta name="author" content="Basho Technologies" />
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<meta name="description" content="Webmachine examples" />
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<meta name="keywords" content="webmachine http rest web" />
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<meta http-equiv="content-type" content="text/html;charset=utf-8" />
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<link rel="stylesheet" href="css/style-1c.css" type="text/css" />
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<title>Webmachine examples</title>
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</head>
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<body>
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<div id="content">
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<h1><span class="hr"></span><a href="/">webmachine</a></h1>
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<ul id="top">
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<li><a href="/">Home</a></li>
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<li><a href="http://bitbucket.org/justin/webmachine/">Source Code</a></li>
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<li><a href="contact.html">Contact</a></li>
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</ul>
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<div id="left">
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<h3>Webmachine examples</h3>
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<p>
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The simplest possible example is the one produced via the
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<a href="quickstart.html">quickstart</a>.
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</p>
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<p>
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For an example of a read/write filesystem server showing several
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interesting features and supporting GET, PUT, DELETE, and POST, see
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<a href="http://bitbucket.org/justin/webmachine/src/tip/demo/src/demo_fs_resource.erl">demo_fs_resource</a>.
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</p>
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<p>
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For a very simple resource demonstrating content negotiation, basic
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auth, and some caching headers, see
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<a href="http://bitbucket.org/justin/webmachine/src/tip/demo/src/webmachine_demo_resource.erl">webmachine_demo_resource</a>.
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</p>
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<p>
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Some example code based on webmachine_demo_resource follows.
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</p>
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<p>
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The simplest working resource could export only one function in
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addition to init/1:
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</p>
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<pre>
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-module(webmachine_demo_resource).
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-export([init/1, to_html/2]).
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-include_lib("webmachine/include/webmachine.hrl").
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init([]) -> {ok, undefined}.
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to_html(ReqData, Context) -> {"<html><body>Hello, new world</body></html>", ReqData, Context}.
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</pre>
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<p>
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That's really it -- a working webmachine resource. That resource will
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respond to all valid GET requests with the exact same response.
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</p>
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<p>
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Many interesting bits of HTTP are handled automatically by
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Webmachine. For instance, if a client sends a request to that trivial
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resource with an Accept header that does not allow for a text/html
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response, they will receive a 406 Not Acceptable.
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</p>
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<p>
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Suppose I wanted to serve a plaintext client as well. I could note
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that I provide more than just HTML:
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</p>
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<pre>
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content_types_provided(ReqData, Context) ->
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{[{"text/html", to_html},{"text/plain",to_text}], ReqData, Context}.
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</pre>
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<p>
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I already have my HTML representation produced, so I add a text one:
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(and while I'm at it, I'll show that it's trivial to produce dynamic content as well)
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</p>
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<pre>
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to_text(ReqData, Context) ->
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Path = wrq:disp_path(ReqData),
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Body = io_lib:format("Hello ~s from webmachine.~n", [Path]),
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{Body, ReqData, Context}.
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</pre>
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<p>
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Now that this resource provides multiple media types, it automatically performs conneg:
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</p>
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<pre>
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$ telnet localhost 8000
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Trying 127.0.0.1...
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Connected to localhost.
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Escape character is '^]'.
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GET /demo/a/resource/path HTTP/1.1
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Accept: text/plain
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HTTP/1.1 200 OK
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Vary: Accept
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Server: MochiWeb/1.1 WebMachine/0.97
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Date: Sun, 15 Mar 2009 02:54:02 GMT
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Content-Type: text/plain
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Content-Length: 39
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Hello a/resource/path from webmachine.
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</pre>
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<p>
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What about authorization? Webmachine resources default to assuming the
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client is authorized, but that can easily be overridden. Here's an
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overly simplistic but illustrative example:
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</p>
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<pre>
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is_authorized(ReqData, Context) ->
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case wrq:disp_path(ReqData) of
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"authdemo" ->
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case wrq:get_req_header("authorization", ReqData) of
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"Basic "++Base64 ->
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Str = base64:mime_decode_to_string(Base64),
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case string:tokens(Str, ":") of
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["authdemo", "demo1"] ->
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{true, ReqData, Context};
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_ ->
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{"Basic realm=webmachine", ReqData, Context}
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end;
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_ ->
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{"Basic realm=webmachine", ReqData, Context}
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end;
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_ -> {true, ReqData, Context}
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end.
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</pre>
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<p>
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With that function in the resource, all paths except
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<code>/authdemo</code> from this resource's root are authorized.
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For that one path,
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the UA will be asked to do basic authorization with the user/pass of
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authdemo/demo1. It should go without saying that this isn't quite the
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same function that we use in our real apps, but it is nice and simple.
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</p>
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<p>
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If you've generated the application from the
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<a href="quickstart.html">quickstart</a>, make sure
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you've added this line to your dispatch.conf file:
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</p>
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<pre>
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{["demo", '*'], mywebdemo_resource, []}.
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</pre>
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<p>
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Now you can point your browser at
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<code>http://localhost:8000/demo/authdemo</code> with the demo app running:
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</p>
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<pre>
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$ curl -v http://localhost:8000/demo/authdemo
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> GET /demo/authdemo HTTP/1.1
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> Host: localhost:8000
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> Accept: */*
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>
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< HTTP/1.1 401 Unauthorized
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< WWW-Authenticate: Basic realm=webmachine
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< Server: MochiWeb/1.1 WebMachine/0.97
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< Date: Sun, 15 Mar 2009 02:57:43 GMT
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< Content-Length: 0
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<
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</pre>
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<p></p>
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<pre>
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$ curl -v -u authdemo:demo1 http://localhost:8000/demo/authdemo
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* Server auth using Basic with user 'authdemo'
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> GET /demo/authdemo HTTP/1.1
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> Authorization: Basic YXV0aGRlbW86ZGVtbzE=
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> Host: localhost:8000
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> Accept: */*
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>
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< HTTP/1.1 200 OK
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< Vary: Accept
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< Server: MochiWeb/1.1 WebMachine/0.97
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< Date: Sun, 15 Mar 2009 02:59:02 GMT
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< Content-Type: text/html
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< Content-Length: 59
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<
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<html><body>Hello authdemo from webmachine.
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</body></html>
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</pre>
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<p>
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HTTP caching support is also quite easy, with functions allowing
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resources to define (e.g.) <code>last_modified</code>,
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<code>expires</code>, and <code>generate_etag.</code> For instance, since
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representations of this resource vary only by URI Path, I could use an
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extremely simple entity tag unfit for most real applications but
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sufficient for this example:
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</p>
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<pre>
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generate_etag(ReqData, Context) -> {wrq:raw_path(ReqData), ReqData, Context}.
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</pre>
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<p>Similarly, here's a trivial expires rule:</p>
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<pre>
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expires(ReqData, Context) -> {{{2021,1,1},{0,0,0}}, ReqData, Context}.
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</pre>
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<p>
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And now the response from our earlier request is appropriately tagged:
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</p>
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<pre>
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HTTP/1.1 200 OK
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Vary: Accept
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Server: MochiWeb/1.1 WebMachine/0.97
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Expires: Fri, 01 Jan 2021 00:00:00 GMT
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ETag: /demo/authdemo
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Date: Sun, 15 Mar 2009 02:59:02 GMT
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Content-Type: text/html
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Content-Length: 59
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<html><body>Hello authdemo from webmachine.
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</body></html>
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</pre>
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<p>
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For more details, read the source of the resources linked at the top
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of this page.
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</p>
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</div>
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<div id="footer">
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</div>
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</div>
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<script type="text/javascript">
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var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www.");
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document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E"));
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</script>
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<script type="text/javascript">
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try {
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var pageTracker = _gat._getTracker("UA-4979965-5");
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pageTracker._trackPageview();
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} catch(err) {}</script>
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</body>
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</html>
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