Difference between revisions of "WebSocket Module"
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* The module will be available if the {{Code|basex-api}} library is found in the classpath. This is the case if you use one of the complete distributions of BaseX (zip, exe, war). | * The module will be available if the {{Code|basex-api}} library is found in the classpath. This is the case if you use one of the complete distributions of BaseX (zip, exe, war). | ||
− | * All functions and errors are assigned to the <code><nowiki>http://basex.org/modules/ws</nowiki></code> namespace, which is statically bound to the {{Code|ws}} prefix. | + | * All functions and errors are assigned to the <code><nowiki>http://basex.org/modules/ws</nowiki></code> namespace, which is statically bound to the {{Code|ws}} prefix. |
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* As sessions are side-effecting operations, all functions are flagged as ''non-deterministic''. As a result, some query optimizations will be suppressed. | * As sessions are side-effecting operations, all functions are flagged as ''non-deterministic''. As a result, some query optimizations will be suppressed. | ||
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==ws:eval== | ==ws:eval== | ||
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{| width='100%' | {| width='100%' | ||
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|- | |- | ||
| '''Summary''' | | '''Summary''' | ||
− | |Schedules the evaluation of the supplied {{Code|$query}} and returns the result to the calling WebSocket client. The query can be a URI or a string, and variables and context items can be declared via {{Code|$bindings}} (see {{ | + | |Schedules the evaluation of the supplied {{Code|$query}} and returns the result to the calling WebSocket client. The query can be a URI or a string, and variables and context items can be declared via {{Code|$bindings}} (see {{Function|XQuery|xquery:eval}} for more details). The following {{Code|$options}} can be supplied: |
* {{Code|base-uri}}: sets the [https://www.w3.org/TR/xquery-31/#dt-static-base-uri base-uri property] for the query. This URI will be used when resolving relative URIs, such as with {{Code|fn:doc}}. | * {{Code|base-uri}}: sets the [https://www.w3.org/TR/xquery-31/#dt-static-base-uri base-uri property] for the query. This URI will be used when resolving relative URIs, such as with {{Code|fn:doc}}. | ||
* {{Code|id}}: sets a custom job id. The id must not start with the standard <code>job</code> prefix, and it can only be assigned if no job with the same name exists. | * {{Code|id}}: sets a custom job id. The id must not start with the standard <code>job</code> prefix, and it can only be assigned if no job with the same name exists. | ||
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| '''Examples''' | | '''Examples''' | ||
| | | | ||
− | * | + | * Schedule a second query that will notify the client 10 seconds later that a message was processed: |
<pre class='brush:xquery'> | <pre class='brush:xquery'> | ||
declare | declare | ||
%ws:message('/tasks', '{$message}') | %ws:message('/tasks', '{$message}') | ||
function local:message($message) { | function local:message($message) { | ||
− | ws:eval('Your message has been processed.') | + | ws:eval('prof:sleep(10000), "Your message has been processed."') |
}; | }; | ||
</pre> | </pre> |
Revision as of 06:55, 29 November 2019
This XQuery Module contains functions for accessing specific WebSocket functions. This module is mainly useful in the context of WebSockets.
Contents
Conventions
- The module will be available if the
basex-api
library is found in the classpath. This is the case if you use one of the complete distributions of BaseX (zip, exe, war). - All functions and errors are assigned to the
http://basex.org/modules/ws
namespace, which is statically bound to thews
prefix. - As sessions are side-effecting operations, all functions are flagged as non-deterministic. As a result, some query optimizations will be suppressed.
General Functions
ws:id
Signatures | ws:id() as xs:string
|
Summary | Returns the ID of the current WebSocket. |
Errors | not-found : No WebSocket with the specified id exists.
|
ws:ids
Signatures | ws:ids() as xs:string*
|
Summary | Returns the ids of all currently registered WebSocket. |
ws:path
Signatures | ws:path($id as xs:string) as xs:string
|
Summary | Returns the path of the WebSocket with the specified $id .
|
Errors | not-found : No WebSocket with the specified id exists.
|
ws:close
Signatures | ws:close($id as xs:string) as empty-sequence()
|
Summary | Closes the connection of the WebSocket with the specified $id .
|
Errors | not-found : No WebSocket with the specified id exists.
|
Sending Data
ws:send
Signatures | ws:send($message as item(), $ids as xs:string*) as empty-sequence()
|
Summary | Sends a $message to the clients with the specified $ids . Ids that cannot be assigned to clients will be ignored. The message will be handled as follows:
|
ws:broadcast
Signatures | ws:broadcast($message as xs:anyAtomicType) as empty-sequence()
|
Summary | Broadcasts a $message to all connected clients except to the caller. Invocations of this convenience function are equivalent to ws:send($message, ws:ids()[. != ws:id()]) . See ws:send for more details on the message handling.
|
ws:emit
Signatures | ws:emit($message as xs:anyAtomicType) as empty-sequence()
|
Summary | Emits a $message to all connected clients. Invocations of this function are equivalent to ws:send($message, ws:ids()) . See ws:send for more details on the message handling.
|
ws:eval
Signatures | ws:eval($query as xs:anyAtomicItem) as xs:string ws:eval($query as xs:anyAtomicItem, $bindings as map(*)?) as xs:string ws:eval($query as xs:anyAtomicItem, $bindings as map(*)?, $options as map(*)?) as xs:string |
Summary | Schedules the evaluation of the supplied $query and returns the result to the calling WebSocket client. The query can be a URI or a string, and variables and context items can be declared via $bindings (see xquery:eval for more details). The following $options can be supplied:
Query scheduling is recommendable if the immediate query execution might be too time consuming and lead to a timeout. |
Errors | overflow : Query execution is rejected, because too many jobs are queued or being executed. id : The specified id is invalid or has already been assigned.
|
Examples |
declare %ws:message('/tasks', '{$message}') function local:message($message) { ws:eval('prof:sleep(10000), "Your message has been processed."') }; |
WebSocket Attributes
ws:get
Signatures | ws:get($id as xs:string, $name as xs:string) as item()* ws:get($id as xs:string, $name as xs:string, $default as item()*) as item()*
|
Summary | Returns the value of an attribute with the specified $name from the WebSocket with the specified $id . If the attribute is unknown, an empty sequence or the optionally specified $default value will be returned instead.
|
Errors | not-found : No WebSocket with the specified id exists.
|
ws:set
Signatures | ws:set($id as xs:string, $name as xs:string, $value as item()*) as empty-sequence()
|
Summary | Returns the specified value of the attribute with the specified $name from the WebSocket with the specified $id .
|
Errors | not-found : No WebSocket with the specified id exists.set : The supplied value cannot be materialized.
|
ws:delete
Signatures | ws:delete($id as xs:string, $name as xs:string) as empty-sequence()
|
Summary | Deletes an attribute with the specified $name from the WebSocket with the specified $id .
|
Errors | not-found : No WebSocket with the specified id exists.
|
Examples
Example 1
import module namespace ws = "http://basex.org/modules/ws"; declare %ws:connect('/') function local:connect() as empty-sequence() { let $id := ws:id() let $message := json:serialize(map { 'type': 'Connect', 'id': $id }) return ws:broadcast($message) };
Explanation:
- The function has a
%ws:connect
annotation. It gets called if a client successfully creates a WebSocket connection to the path/
(check out WebSockets for further information). - A JSON response is generated, which contains the new client id and a
Connect
string. - This response will be sent to all other connected clients.
Example 2
import module namespace ws = "http://basex.org/modules/ws"; declare %ws:message('/', '{$message}') function local:message( $message as xs:string ) as empty-sequence() { let $message := json:serialize(map { 'message': $message }) return ws:emit($message) };
Explanation:
- The function has a
%ws:message
annotation. It gets called if a client sends a new message. - A JSON response is generated, which contains the message string.
- This response will be sent to all connected clients (including the calling client).
Errors
Code | Description |
---|---|
set
|
The supplied value cannot be materialized. |
not-found
|
No WebSocket with the specified id exists. |
Changelog
- Version 9.2
- Added: ws:eval
This module was introduced with Version 9.1.