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Whenever If a RESTXQ URL is requested, the [[Options#RESTXQPATH|RESTXQPATH]] module directory and its sub-directories will be traversed, and all [[XQuery Extensions#Suffixes|XQuery files]] will be parsed for functions with RESTXQ annotations in library modules (detected by the extension {{Code|.xqm}}) and main modules (detected by Sub-directories that include an {{Code|.xqignore}}). In main expressions, the main module file will never be evaluated. All modules will be cached and parsed again when their timestamp changesskipped.
The following features To speed up processing, the functions of the existing XQuery modules are available with {{Version|8automatically cached in main memory. Functions will be invalidated and parsed again if the timestamp of their module changes.3}}:
function page:hello-postman( $message as xs:string, $agent as xs:string*) as element(response){
function page:multipart($data as item()*){
function page:params($id as xs:string?, $add as xs:integer+){
function page:upload($files){
function page:cities(){
function page:html(){
function page:check($user){
function page:user-error($user){
Currently, the following external resources on RESTXQ existDocumentation:
[[Category:HTTP]]
[[Category:Developer]]
→Preliminaries
HTTP responses.
Please note that BaseX provides various extensions to the official original draft of the specification:
* Multipart types are supported, including {{Code|multipart/form-data}}
* Quality factors in the [[#Content Negotiation|Accept header]] will be evaluated
* <code>%input</code> annotations, support for input-specific content-type parameters
* <code>%rest:single</code> annotation to cancel running RESTXQ functions
<br />
All RESTXQ [[XQuery 3.0#Annotations|annotations]] are assigned to the <code><nowiki>http://exquery.org/ns/restxq</nowiki></code> namespace, which is statically bound to the {{Code|rest}} prefix. A ''Resource Function'' is an XQuery function that has been marked up with RESTXQ annotations. When an HTTP request comes in, a resource function will be invoked that matches the constraints indicated by its annotations.
{{Mark|Updated with Version 8.6:}} * Module caching RESTXQ file monitoring has been improved and can be turned on by setting adjusted via the new [[Options#CACHERESTXQPARSERESTXQ|CACHERESTXQPARSERESTXQ]] to trueoption. This option is particularly helpful in In productive environments with a high load, it may be recommendable to change the timeout, or completely disable monitoring.* The If files are replaced while the web server is running, the RESTXQ module cache should be explicitly invalidated by calling the static root path {{Code|/.init}} can be called to invalidate or by calling the [[RESTXQ module cacheModule#rest:init|rest:init]] function.* A sub-directory will be skipped if it contains a file named {{Code|.ignore}}Authentication was readded to RESTXQ (see [[Web Application]] for more details).
==Examples==
%rest:form-param("message","{$message}", "(no message)")
%rest:header-param("User-Agent", "{$agent}")
<response type='form'>
<message>{ $message }</message>
| {{Code|application/json}}
| [[JSON Module#Options|JSON Options]]
| {{Code|document-node()}} or {{Code|map(*)}}
|-
| {{Code|text/html}}
| {{Code|text/comma-separated-values}}
| [[CSV Module#Options|CSV Options]]
| {{Code|document-node()}} or {{Code|map(*)}}
|-
| ''others''
===Input options===
Conversion options for [[Options#JSONPARSER|JSON]], [[Options#CSVPARSER|CSV ]] and [[Options#HTMLPARSER|HTML ]] can also be specified via annotations using with the <code>input</code> prefix. The following function interprets the input as text with the CP1252 encoding and treats the first line of the textual input as CSV header:
<pre class="brush:xquery">
%rest:path("/store.csv")
%rest:POST("{$csv}")
%input:csv("header=true,encoding=CP1252") function page:store-csv($csv as document-node()){
"Number of rows: " || count($csv/csv/record)
};
%rest:POST("{$data}")
%rest:consumes("multipart/mixed") (: optional :)
"Number of items: " || count($data)
};
%rest:query-param("id", "{$id}")
%rest:query-param("add", "{$add}", 42, 43, 44)
<result id="{ $id }" sum="{ sum($add) }"/>
};
%rest:path("/upload")
%rest:form-param("files", "{$files}")
for $name in map:keys($files)
let $content := $files($name)
%rest:cookie-param("authentication", "{$auth}", "no_auth")
</pre>
==Query Execution==
In many RESTXQ search scenarios, input from browser forms is processed and search results are returned. User experience can generally be made more interactive if an updated search request is triggered with each key click. However, this may lead to many expensive parallel requests, from which only the result of the last request will be relevant for the client.
With the <code>%rest:single</code> annotation, it can be enforced that only one instance of a function will be executed for the same client. If the same function will be called for the second time, the already running query will be stopped, and the HTTP error code {{Code|410}} (Gone) will be returned instead:
<pre class="brush:xquery">
(: If fast enough, returns the result. Otherwise, if called again, raises 410 :)
declare
%rest:path("/search")
%rest:query-param("term", "{$term}")
%rest:single
function page:search($term as xs:string) {
<ul>{
for $result in db:open('large-db')//*[text() = $term]
return <li>{ $result }</li>
}</ul>
};
</pre>
By specifying a string along with the annotation, functions can be bundled together, and one request can be canceled by calling another one.
This is shown by another example, in which the first function can be interrupted by the second one. If you call both functions in separate browser tabs, you will note that the first tab will return <code>410</code>, and the second one will return <xml>stopped</xml>.
<pre class="brush:xquery">
declare
%rest:path("/compute")
%rest:single("EXPENSIVE")
function local:compute() {
(1 to 100000000000000)[. = 0]
};
declare
%rest:path("/stop")
%rest:single("EXPENSIVE")
function local:stop() {
<xml>stopped</xml>
};
</pre>
The following things should be noted:
* If a query will be canceled, there will be no undesirable side-effects. For example, it won’t be possible to kill a query if it is currenly updating the database or perfoming any other I/O operations. As a result, the termination of a running query can take some more time as expected.
* The currently executed function is bound to the current session. This way, a client will not be able to cancel requests from other clients. As a result, functions can only be stopped if there was at least one previous successful response, in which initial session data was returned to the client.
=Response=
%output:method("json")
%output:json("format=jsonml")
element cities {
db:open('factbook')//city/name
<pre class="brush:xquery">
declare
%rest:path("done")
%output:method("xhtml")
%output:omit-xml-declaration("no")
%output:doctype-public("-//W3C//DTD XHTML 1.0 Transitional//EN")
%output:doctype-system("http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd")
<html xmlns="http://www.w3.org/1999/xhtml">
<body>done</body>
{| class="wikitable"
|- valign="top"
! PriorityPrecedence
! Syntax
! Example
|}
All error codes that are specified for a function must be of have the same priorityprecedence.
The following rules apply when catching errors:
* Codes with a higher priority precedence (smaller number) will be preferredgiven preference.
* A global RESTXQ error will be raised if two functions with conflicting codes are found.
declare
%rest:path("/check/{$user}")
if($user = ('jack', 'lisa'))
then 'User exists'
%rest:error("err:user")
%rest:error-param("description", "{$user}")
'User "' || $user || '" is unknown'
};
</pre>
An XQuery error in a RESTXQ context delivers by default a HTTP status code 400 error back to the client. However, you can also define a custom error code by using the third argument of the error function:
<pre class="brush:xquery">
declare
%rest:path("/teapot")
function page:teapot() {
fn:error(xs:QName('error'), "I'm a teapot", 418)
};
</pre>
=References=
* [http://exquery.org/spec/restxq RESTXQ Specification], First Draft
* [http://www.adamretter.org.uk/presentations/restxq_mugl_20120308.pdf RESTXQ]. Slides, MarkLogic User Group London, 2012
* [http://files.basex.org/publications/xmlprague/2013/Develop-RESTXQ-WebApps-with-BaseX.pdf Web Application Development]. Slides from XMLPrague 2013
Examples:
* Sample code combining XQuery and JavaScript: [http://balisage.net/Proceedings/vol17/author-pkg/Galtman01/BalisageVol17-Galtman01.html Materials] and [http://balisage.net/Proceedings/vol17/html/Galtman01/BalisageVol17-Galtman01.html paper] from Amanda Galtman, Balisage 2016.
* [[DBA]]: The Database Administration interface, bundled with the full distributions of BaseX.
=Changelog=
;Version 8.4
* Added: <code>%rest:single</code> annotation
;Version 8.1
* Added: new XML elements {{Code|<rest:redirect/>}} and {{Code|<rest:forward/>}}
