HTTP Client Module

From BaseX Documentation
Jump to navigation Jump to search

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.

If <http:header name="Accept-Encoding" value="gzip"/> is specified and if the addressed web server provides support for the gzip compression algorithm, the response will automatically be decompressed.

Conventions[edit]

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 experr prefix.

Functions[edit]

http:send-request[edit]

Signatures http:send-request($request as element(http:request)) as item()+
http:send-request($request as element(http:request)?, $href as xs:string?) as item()+
http:send-request($request as element(http:request)?, $href as xs:string?, $bodies as item()*) 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 request body can also be supplied via the $bodies parameter.
  • Certificate verification can be globally disabled via the IGNORECERT option.

Notes:

  • Both basic and digest authentication is supported.
  • While the contents of the request can be supplied as child of the http:body element, it is faster and safer to pass them on via the third argument.
  • For further information, please check out 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.

Examples[edit]

Status Only[edit]

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>

Google Homepage[edit]

Retrieve the Google search home page with a timeout of 10 seconds. In order to parse HTML, TagSoup must be contained in the class path.

Query:

http:send-request(<http:request method='get' href='http://www.google.com' timeout='10'/>)

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=UTF-8"/>
    <title>Google</title>
    ...
  </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). With the http:header element, a custom user agent can be set. See the following example:

Query:

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

SVG Data[edit]

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/&quot;11b6d-4ba15ed4&quot;"/>
  <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>

POST Request[edit]

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

Query:

http:send-request(
  <http:request method='post' username='admin' password='admin'>
    <http:body media-type='application/xml'/>
  </http:request>,
  'http://localhost:8984/rest',
  <query>
    <text>
      <html>{
        for $i in 1 to 3
        return <div>Section {$i }</div>
      }</html>
   </text>
  </query>
)

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>

File Upload[edit]

Performs an HTML file upload. In the RESTXQ code, the uploaded file is written to the temporary directory:

Query:

let $path := 'file-to-be.uploaded'
return http:send-request(
  <http:request method='POST'>
    <http:multipart media-type='multipart/form-data'>
      <http:header name='content-disposition'
        value='form-data; name="files"; filename="{ file:name($path) }"'/>
      <http:body media-type='application/octet-stream'/>
    </http:multipart>
  </http:request>,
  'http://localhost:8984/write-to-temp',
  file:read-binary($path)
)

RESTXQ service:

declare
  %rest:POST
  %rest:path('/write-to-temp')
  %rest:form-param('files', '{$files}')
function dba:file-upload(
  $files  as map(xs:string, xs:base64Binary)
) as empty-sequence() {
  map:for-each($files, function($file, $content) {
    file:write-binary(file:temp-dir() || $file, $content)
  });
};

Errors[edit]

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.

Changelog[edit]

Version 9.0
  • Updated: support for gzipped content encoding
Version 8.0
  • Added: digest authentication
Version 7.6
  • Updated: http:send-request: HC0002 is raised if the input cannot be parsed or converted to the final data type.
  • Updated: errors are using text/plain as media-type.