Difference between revisions of "Fetch Module"
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− | This [[Module Library|XQuery Module]] provides simple functions to fetch the content of resources identified by URIs. Resources can be stored locally or remotely and e.g. use the {{Code|file://}} or {{Code|http://}} scheme. If more control over HTTP requests is required, the [[HTTP Module]] can be used. With the [[HTML Module]], retrieved HTML documents can be converted to XML. | + | This [[Module Library|XQuery Module]] provides simple functions to fetch the content of resources identified by URIs. Resources can be stored locally or remotely and e.g. use the {{Code|file://}} or {{Code|http://}} scheme. If more control over HTTP requests is required, the [[HTTP Client Module]] can be used. With the [[HTML Module]], retrieved HTML documents can be converted to XML. |
=Conventions= | =Conventions= | ||
− | All functions in this module are assigned to the <code><nowiki>http://basex.org/modules/fetch</nowiki></code> namespace, which is statically bound to the {{Code|fetch}} prefix.<br/> | + | All functions and errors in this module are assigned to the <code><nowiki>http://basex.org/modules/fetch</nowiki></code> namespace, which is statically bound to the {{Code|fetch}} prefix.<br/> |
− | |||
URI arguments can point be URLs or point to local files. Relative file paths will be resolved against the ''current working directory'' (for more details, have a look at the [[File Module#File Paths|File Module]]). | URI arguments can point be URLs or point to local files. Relative file paths will be resolved against the ''current working directory'' (for more details, have a look at the [[File Module#File Paths|File Module]]). | ||
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==fetch:binary== | ==fetch:binary== | ||
+ | |||
{| width='100%' | {| width='100%' | ||
|- | |- | ||
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|- | |- | ||
| '''Summary''' | | '''Summary''' | ||
− | |Fetches the resource referred to by the given URI and returns it as [[ | + | |Fetches the resource referred to by the given URI and returns it as [[Lazy Module|lazy]] {{Code|xs:base64Binary}} item. |
|- | |- | ||
| '''Errors''' | | '''Errors''' | ||
− | |{{Error| | + | |{{Error|open|#Errors}} the URI could not be resolved, or the resource could not be retrieved. |
|- | |- | ||
| '''Examples''' | | '''Examples''' | ||
| | | | ||
* <code><nowiki>fetch:binary("http://images.trulia.com/blogimg/c/5/f/4/679932_1298401950553_o.jpg")</nowiki></code> returns the addressed image. | * <code><nowiki>fetch:binary("http://images.trulia.com/blogimg/c/5/f/4/679932_1298401950553_o.jpg")</nowiki></code> returns the addressed image. | ||
− | * <code><nowiki> | + | * <code><nowiki>lazy:cache(fetch:binary("http://en.wikipedia.org"))</nowiki></code> enforces the fetch operation (otherwise, it will be delayed until requested first). |
|} | |} | ||
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|- | |- | ||
| '''Summary''' | | '''Summary''' | ||
− | |Fetches the resource referred to by the given {{Code|$uri}} and returns it as [[ | + | |Fetches the resource referred to by the given {{Code|$uri}} and returns it as [[Lazy Module|lazy]] {{Code|xs:string}} item: |
* The UTF-8 default encoding can be overwritten with the optional {{Code|$encoding}} argument. | * The UTF-8 default encoding can be overwritten with the optional {{Code|$encoding}} argument. | ||
* By default, invalid characters will be rejected. If {{Code|$fallback}} is set to true, these characters will be replaced with the Unicode replacement character <code>FFFD</code> (�). | * By default, invalid characters will be rejected. If {{Code|$fallback}} is set to true, these characters will be replaced with the Unicode replacement character <code>FFFD</code> (�). | ||
|- | |- | ||
| '''Errors''' | | '''Errors''' | ||
− | |{{Error| | + | |{{Error|open|#Errors}} the URI could not be resolved, or the resource could not be retrieved.<br/>{{Error|encoding|#Errors}} the specified encoding is not supported, or unknown. |
|- | |- | ||
| '''Examples''' | | '''Examples''' | ||
| | | | ||
* <code><nowiki>fetch:text("http://en.wikipedia.org")</nowiki></code> returns a string representation of the English Wikipedia main HTML page. | * <code><nowiki>fetch:text("http://en.wikipedia.org")</nowiki></code> returns a string representation of the English Wikipedia main HTML page. | ||
− | * <code><nowiki> | + | * <code><nowiki>fetch:text("http://www.bbc.com","US-ASCII",true())</nowiki></code> returns the BBC homepage in US-ASCII with all non-US-ASCII characters replaced with �. |
+ | * <code><nowiki>lazy:cache(fetch:text("http://en.wikipedia.org"))</nowiki></code> enforces the fetch operation (otherwise, it will be delayed until requested first). | ||
|} | |} | ||
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|- | |- | ||
| width='120' | '''Signatures''' | | width='120' | '''Signatures''' | ||
− | |{{Func|fetch:xml|$uri as xs:string|document-node()}}<br/>{{Func|fetch:xml|$uri as xs:string, $options as map(*)|document-node()}} | + | |{{Func|fetch:xml|$uri as xs:string|document-node()}}<br/>{{Func|fetch:xml|$uri as xs:string, $options as map(*)?|document-node()}} |
|- | |- | ||
| '''Summary''' | | '''Summary''' | ||
− | |Fetches the resource referred to by the given {{Code|$uri}} and returns it as | + | |Fetches the resource referred to by the given {{Code|$uri}} and returns it as document node.<br/>The {{Code|$options}} argument can be used to change the parsing behavior. Allowed options are all [[Options#Parsing|parsing]] and [[Options#XML Parsing|XML parsing]] options in lower case.<br/>The function is different to <code>fn:doc</code> in various aspects: |
+ | * As it is non-deterministic, a new document node will be created by each call of this function. | ||
+ | * A document created by this function will be garbage-collected as soon as it is not referenced anymore. | ||
+ | * URIs will not be resolved against existing databases. As a result, it will not trigger any locks (see [[Transaction Management#Limitations|limitations of database locking]] for more details). | ||
|- | |- | ||
| '''Errors''' | | '''Errors''' | ||
− | |{{Error| | + | |{{Error|open|#Errors}} the URI could not be resolved, or the resource could not be retrieved. |
|- | |- | ||
| '''Examples''' | | '''Examples''' | ||
− | | | + | | |
− | < | + | * Retrieve an XML representation of the English Wikipedia main HTML page, chop all whitespace nodes: |
+ | <syntaxhighlight lang="xquery"> | ||
fetch:xml("http://en.wikipedia.org", map { 'chop': true() }) | fetch:xml("http://en.wikipedia.org", map { 'chop': true() }) | ||
− | </ | + | </syntaxhighlight> |
+ | * Return a document located in the current base directory: | ||
+ | <syntaxhighlight lang="xquery"> | ||
+ | fetch:xml(file:base-dir() || "example.xml") | ||
+ | </syntaxhighlight> | ||
+ | * Return a web page as XML, preserve namespaces: | ||
+ | <syntaxhighlight lang="xquery"> | ||
+ | fetch:xml( | ||
+ | 'http://basex.org/', | ||
+ | map { | ||
+ | 'parser': 'html', | ||
+ | 'htmlparser': map { 'nons': false() } | ||
+ | } | ||
+ | ) | ||
+ | </syntaxhighlight> | ||
+ | |} | ||
+ | |||
+ | ==fetch:xml-binary== | ||
+ | |||
+ | {| width='100%' | ||
+ | |- | ||
+ | | width='120' | '''Signatures''' | ||
+ | |{{Func|fetch:xml-binary|$data as xs:base64Binary|document-node()}}<br/>{{Func|fetch:xml-binary|$data as xs:base64Binary, $options as map(*)?|document-node()}} | ||
+ | |- | ||
+ | | '''Summary''' | ||
+ | |Parses binary {{Code|$data}} and returns it as document node.<br/>In contrast to fn:parse-xml, which expects an XQuery string, the input of this function can be arbitrarily encoded. The encoding will be derived from the XML declaration or (in case of UTF16 or UTF32) from the first bytes of the input.<br/>The {{Code|$options}} argument can be used to change the parsing behavior. Allowed options are all [[Options#Parsing|parsing]] and [[Options#XML Parsing|XML parsing]] options in lower case. | ||
+ | |- | ||
+ | | '''Examples''' | ||
+ | | | ||
+ | * Retrieves file input as binary data and parses it as XML: | ||
+ | <syntaxhighlight lang="xquery"> | ||
+ | fetch:xml-binary(file:read-binary('doc.xml')) | ||
+ | </syntaxhighlight> | ||
+ | * Encodes a string as CP1252 and parses it as XML. The input and the string {{Code|touché}} will be correctly decoded because of the XML declaration: | ||
+ | <syntaxhighlight lang="xquery"> | ||
+ | fetch:xml-binary(convert:string-to-base64( | ||
+ | "<?xml version='1.0' encoding='CP1252'?><xml>touché</xml>", | ||
+ | "CP1252" | ||
+ | )) | ||
+ | </syntaxhighlight> | ||
+ | * Encodes a string as UTF16 and parses it as XML. The document will be correctly decoded, as the first bytes of the data indicate that the input must be UTF16: | ||
+ | <syntaxhighlight lang="xquery"> | ||
+ | fetch:xml-binary(convert:string-to-base64("<xml/>", "UTF16")) | ||
+ | </syntaxhighlight> | ||
|} | |} | ||
==fetch:content-type== | ==fetch:content-type== | ||
+ | |||
{| width='100%' | {| width='100%' | ||
|- | |- | ||
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|- | |- | ||
| '''Errors''' | | '''Errors''' | ||
− | |{{Error| | + | |{{Error|open|#Errors}} the URI could not be resolved, or the resource could not be retrieved. |
|- | |- | ||
| '''Examples''' | | '''Examples''' | ||
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|Description | |Description | ||
|- | |- | ||
− | |{{Code| | + | |{{Code|encoding}} |
+ | |The specified encoding is not supported, or unknown. | ||
+ | |- | ||
+ | |{{Code|open}} | ||
|The URI could not be resolved, or the resource could not be retrieved. | |The URI could not be resolved, or the resource could not be retrieved. | ||
− | |||
− | |||
− | |||
|} | |} | ||
=Changelog= | =Changelog= | ||
+ | |||
+ | ;Version 9.0 | ||
+ | |||
+ | * Added: [[#fetch:xml-binary|fetch:xml-binary]] | ||
+ | * Updated: error codes updated; errors now use the module namespace | ||
;Version 8.5 | ;Version 8.5 |
Revision as of 16:21, 27 February 2020
This XQuery Module provides simple functions to fetch the content of resources identified by URIs. Resources can be stored locally or remotely and e.g. use the file://
or http://
scheme. If more control over HTTP requests is required, the HTTP Client Module can be used. With the HTML Module, retrieved HTML documents can be converted to XML.
Contents
Conventions
All functions and errors in this module are assigned to the http://basex.org/modules/fetch
namespace, which is statically bound to the fetch
prefix.
URI arguments can point be URLs or point to local files. Relative file paths will be resolved against the current working directory (for more details, have a look at the File Module).
Functions
fetch:binary
Signatures | fetch:binary($uri as xs:string) as xs:base64Binary |
Summary | Fetches the resource referred to by the given URI and returns it as lazy xs:base64Binary item.
|
Errors | open : the URI could not be resolved, or the resource could not be retrieved.
|
Examples |
|
fetch:text
Signatures | fetch:text($uri as xs:string) as xs:string fetch:text($uri as xs:string, $encoding as xs:string) as xs:string fetch:text($uri as xs:string, $encoding as xs:string, $fallback as xs:boolean) as xs:string |
Summary | Fetches the resource referred to by the given $uri and returns it as lazy xs:string item:
|
Errors | open : the URI could not be resolved, or the resource could not be retrieved.encoding : the specified encoding is not supported, or unknown.
|
Examples |
|
fetch:xml
Signatures | fetch:xml($uri as xs:string) as document-node() fetch:xml($uri as xs:string, $options as map(*)?) as document-node()
|
Summary | Fetches the resource referred to by the given $uri and returns it as document node.The $options argument can be used to change the parsing behavior. Allowed options are all parsing and XML parsing options in lower case.The function is different to fn:doc in various aspects:
|
Errors | open : the URI could not be resolved, or the resource could not be retrieved.
|
Examples |
<syntaxhighlight lang="xquery"> fetch:xml("http://en.wikipedia.org", map { 'chop': true() }) </syntaxhighlight>
<syntaxhighlight lang="xquery"> fetch:xml(file:base-dir() || "example.xml") </syntaxhighlight>
<syntaxhighlight lang="xquery"> fetch:xml( 'http://basex.org/', map { 'parser': 'html', 'htmlparser': map { 'nons': false() } } ) </syntaxhighlight> |
fetch:xml-binary
Signatures | fetch:xml-binary($data as xs:base64Binary) as document-node() fetch:xml-binary($data as xs:base64Binary, $options as map(*)?) as document-node()
|
Summary | Parses binary $data and returns it as document node.In contrast to fn:parse-xml, which expects an XQuery string, the input of this function can be arbitrarily encoded. The encoding will be derived from the XML declaration or (in case of UTF16 or UTF32) from the first bytes of the input. The $options argument can be used to change the parsing behavior. Allowed options are all parsing and XML parsing options in lower case.
|
Examples |
<syntaxhighlight lang="xquery"> fetch:xml-binary(file:read-binary('doc.xml')) </syntaxhighlight>
<syntaxhighlight lang="xquery"> fetch:xml-binary(convert:string-to-base64( "<?xml version='1.0' encoding='CP1252'?><xml>touché</xml>", "CP1252" )) </syntaxhighlight>
<syntaxhighlight lang="xquery"> fetch:xml-binary(convert:string-to-base64("<xml/>", "UTF16")) </syntaxhighlight> |
fetch:content-type
Signatures | fetch:content-type($uri as xs:string) as xs:string |
Summary | Returns the content-type (also called mime-type) of the resource specified by $uri :
|
Errors | open : the URI could not be resolved, or the resource could not be retrieved.
|
Examples |
|
Errors
Code | Description |
---|---|
encoding
|
The specified encoding is not supported, or unknown. |
open
|
The URI could not be resolved, or the resource could not be retrieved. |
Changelog
- Version 9.0
- Added: fetch:xml-binary
- Updated: error codes updated; errors now use the module namespace
- Version 8.5
- Updated: fetch:text:
$fallback
argument added.
- Version 8.0
- Added: fetch:xml
The module was introduced with Version 7.6.