HTTP Module

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This XQuery Module contains a single function to send HTTP requests and handle HTTP responses. The function send-request is based on the EXPath HTTP Client Module. It gives full control over the available request and response parameters. For simple GET requests, the Fetch Module may be sufficient.

Contents

[edit] Conventions

All functions in this module are assigned to the http://expath.org/ns/http-client namespace, which is statically bound to the http prefix.
All errors are assigned to the http://expath.org/ns/error namespace, which is statically bound to the exerr prefix.

[edit] Functions

[edit] http:send-request

Signatures http:send-request($request as element(http:request)?, $href as xs:string?, $bodies as item()*) as item()+
http:send-request($request as element(http:request)) as item()+
http:send-request($request as element(http:request)?, $href as xs:string?) as item()+
Summary Sends an HTTP request and interprets the corresponding response. $request contains the parameters of the HTTP request such as HTTP method and headers. In addition to this it can also contain the URI to which the request will be sent and the body of the HTTP method. If the URI is not given with the parameter $href, its value in $request is used instead. The structure of http:request element follows the EXPath specification.
Errors HC0001: an HTTP error occurred.
HC0002: error parsing the entity content as XML or HTML.
HC0003: with a multipart response, the override-media-type must be either a multipart media type or application/octet-stream.
HC0004: the src attribute on the body element is mutually exclusive with all other attribute (except the media-type).
HC0005: the request element is not valid.
HC0006: a timeout occurred waiting for the response.
Notes The attribute auth-method of $request is not considered in our implementation because we are handling only basic authentication.

[edit] Examples

[edit] Status Only

Simple GET request. As the attribute status-only is set to true, only the response element is returned.

Query:

http:send-request(<http:request method='get' status-only='true'/>, 'http://basex.org')

Result:

<http:response status="200" message="OK">
  <http:header name="Date" value="Mon, 14 Mar 2011 20:55:53 GMT"/>
  <http:header name="Content-Length" value="12671"/>
  <http:header name="Expires" value="Mon, 14 Mar 2011 20:57:23 GMT"/>
  <http:header name="Set-Cookie" value="fe_typo_user=d10c9552f9a784d1a73f8b6ebdf5ce63; path=/"/>
  <http:header name="Connection" value="close"/>
  <http:header name="Content-Type" value="text/html; charset=utf-8"/>
  <http:header name="Server" value="Apache/2.2.16"/>
  <http:header name="X-Powered-By" value="PHP/5.3.5"/>
  <http:header name="Cache-Control" value="max-age=90"/>
  <http:body media-type="text/html; charset=utf-8"/>
</http:response>

[edit] Google Homepage

Retrieve Google search home page. TagSoup must be contained in the class path in order to parse html.

Query:

http:send-request(<http:request method='get' href='http://www.google.com'/>)

Result:

<http:response status="200" message="OK">
  <http:header name="Date" value="Mon, 14 Mar 2011 22:03:25 GMT"/>
  <http:header name="Transfer-Encoding" value="chunked"/>
  <http:header name="Expires" value="-1"/>
  <http:header name="X-XSS-Protection" value="1; mode=block"/>
  <http:header name="Set-Cookie" value="...; expires=Tue, 13-Sep-2011 22:03:25 GMT; path=/; domain=.google.ch; HttpOnly"/>
  <http:header name="Content-Type" value="text/html; charset=ISO-8859-1"/>
  <http:header name="Server" value="gws"/>
  <http:header name="Cache-Control" value="private, max-age=0"/>
  <http:body media-type="text/html; charset=ISO-8859-1"/>
</http:response>
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <meta http-equiv="content-type" content="text/html; charset=ISO-8859-1"/>
    <title>Google</title>
    <script>window.google={kEI:"rZB-
    ... 
    </script>
    </center>
  </body>
</html>

The response content type can also be overwritten in order to retrieve HTML pages and other textual data as plain string (using text/plain) or in its binary representation (using application/octet-stream). The result can then be further processed:

Query:

let $binary :=  http:send-request(
  <http:request method='get'
     override-media-type='application/octet-stream'       
     href='http://www.google.com'/>
)[2]
return try {
  html:parse($binary)
} catch * {
  'Conversion to XML failed: ' || $err:description
}

[edit] SVG Data

Content-type ending with +xml, e.g. image/svg+xml.

Query:

http:send-request(<http:request method='get'/>, 'http://upload.wikimedia.org/wikipedia/commons/6/6b/Bitmap_VS_SVG.svg')

Result:

<http:response status="200" message="OK">
  <http:header name="ETag" value="W/"11b6d-4ba15ed4""/>
  <http:header name="Age" value="9260"/>
  <http:header name="Date" value="Mon, 14 Mar 2011 19:17:10 GMT"/>
  <http:header name="Content-Length" value="72557"/>
  <http:header name="Last-Modified" value="Wed, 17 Mar 2010 22:59:32 GMT"/>
  <http:header name="Content-Type" value="image/svg+xml"/>
  <http:header name="X-Cache-Lookup" value="MISS from knsq22.knams.wikimedia.org:80"/>
  <http:header name="Connection" value="keep-alive"/>
  <http:header name="Server" value="Sun-Java-System-Web-Server/7.0"/>
  <http:header name="X-Cache" value="MISS from knsq22.knams.wikimedia.org"/>
  <http:body media-type="image/svg+xml"/>
</http:response>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" width="1063" height="638">
  <defs>
    <linearGradient id="lg0">
      <stop stop-color="#3333ff" offset="0"/>
      <stop stop-color="#3f3fff" stop-opacity="0" offset="1"/>
    </linearGradient>
    ...
</svg>

[edit] POST Request

POST request to the BaseX REST Service, specifying a username and password.

Query:

let $request :=
  <http:request href='http://localhost:8984/rest'
    method='post' username='admin' password='admin' send-authorization='true'>
    <http:body media-type='application/xml'>
    <query xmlns="http://basex.org/rest">
      <text><![CDATA[
        <html>{
          for $i in 1 to 3
          return <div>Section {$i }</div>
        }</html>
      ]]></text>
    </query>
    </http:body>
  </http:request>
return http:send-request($request)

Result:

<http:response xmlns:http="http://expath.org/ns/http-client" status="200" message="OK">
  <http:header name="Content-Length" value="135"/>
  <http:header name="Content-Type" value="application/xml"/>
  <http:header name="Server" value="Jetty(6.1.26)"/>
  <http:body media-type="application/xml"/>
</http:response>
<html>
  <div>Section 1</div>
  <div>Section 2</div>
  <div>Section 3</div>
</html>

[edit] Errors

Code Description
HC0001 An HTTP error occurred.
HC0002 Error parsing the entity content as XML or HTML.
HC0003 With a multipart response, the override-media-type must be either a multipart media type or application/octet-stream.
HC0004 The src attribute on the body element is mutually exclusive with all other attribute (except the media-type).
HC0005 The request element is not valid.
HC0006 A timeout occurred waiting for the response.

[edit] Changelog

Version 7.6
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