Difference between revisions of "WebSocket Module"

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=Conventions=
 
=Conventions=
  
* The {{Code|basex-api}} package must be included in the classpath. This is always the case if you use one of the complete distributions (zip, exe, war) of BaseX.
+
* 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/websocket</nowiki></code> namespace. The module must be imported in the query prolog:
+
* 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.
<pre class="brush:xquery">
+
* As sessions are side-effecting operations, all functions are flagged as ''non-deterministic''. As a result, some query optimizations will be suppressed.
import module namespace ws = "http://basex.org/modules/Websocket";
 
...
 
</pre>
 
  
=Functions=
+
=General Functions=
 +
 
 +
==ws:id==
 +
 
 +
{| width='100%'
 +
|-
 +
| width='120' | '''Signatures'''
 +
|{{Func|ws:id||xs:string}}
 +
|-
 +
| '''Summary'''
 +
|Returns the ID of the current WebSocket.
 +
|-
 +
| '''Errors'''
 +
|{{Error|not-found|#Errors}} No WebSocket with the specified id exists.
 +
|}
 +
 
 +
==ws:ids==
 +
 
 +
{| width='100%'
 +
|-
 +
| width='120' | '''Signatures'''
 +
|{{Func|ws:ids||xs:string*}}
 +
|-
 +
| '''Summary'''
 +
|Returns the ids of all currently registered WebSockets.
 +
|}
 +
 
 +
==ws:path==
 +
 
 +
{| width='100%'
 +
|-
 +
| width='120' | '''Signatures'''
 +
|{{Func|ws:path|$id as xs:string|xs:string}}
 +
|-
 +
| '''Summary'''
 +
|Returns the path of the WebSocket with the specified {{Code|$id}}.
 +
|-
 +
| '''Errors'''
 +
|{{Error|not-found|#Errors}} No WebSocket with the specified id exists.
 +
|}
 +
 
 +
==ws:close==
 +
 
 +
{| width='100%'
 +
|-
 +
| width='120' | '''Signatures'''
 +
|{{Func|ws:close|$id as xs:string|empty-sequence()}}
 +
|-
 +
| '''Summary'''
 +
|Closes the connection of the WebSocket with the specified {{Code|$id}}.
 +
|-
 +
| '''Errors'''
 +
|{{Error|not-found|#Errors}} No WebSocket with the specified id exists.
 +
|}
 +
 
 +
=Sending Data=
  
 
==ws:send==
 
==ws:send==
Line 17: Line 69:
 
|-
 
|-
 
| width='120' | '''Signatures'''
 
| width='120' | '''Signatures'''
|{{Func|ws:send|$message as xs:anyAtomicType, $ids as xs:string* |empty-sequence()}}
+
|{{Func|ws:send|$message as item(), $ids as xs:string*|empty-sequence()}}
 
|-
 
|-
 
| '''Summary'''
 
| '''Summary'''
|Sends a <code>$message</code> which may be of type xs:string, xs:base64Binary, or xs:hexBinary to the user(s) with the ID(s) <code>$ids</code>
+
|Sends a <code>$message</code> to the clients with the specified <code>$ids</code>. Ids that cannot be assigned to clients will be ignored. The message will be handled as follows:
 +
* Items of type {{Code|xs:base64Binary}} and {{Code|xs:hexBinary}} will be transmitted as binary messages.
 +
* Function items (maps, arrays) will be serialized as JSON and transmitted as string messages.
 +
* All other items will be serialized with the default serialization options and transmitted as string messages.
 
|}
 
|}
  
Line 31: Line 86:
 
|-
 
|-
 
| '''Summary'''
 
| '''Summary'''
|Broadcasts <code>$message</code> which may be of type xs:string, xs:base64Binary, or xs:hexBinary to all connected clients except to the caller.  
+
|Broadcasts a <code>$message</code> to all connected clients except to the caller. Invocations of this convenience function are equivalent to <code>ws:send($message, ws:ids()[. != ws:id()])</code>. See [[#ws:send|ws:send]] for more details on the message handling.
 
|}
 
|}
  
Line 42: Line 97:
 
|-
 
|-
 
| '''Summary'''
 
| '''Summary'''
|Emits a <code>message</code> which may be of type xs:string, xs:base64Binary, or xs:hexBinary to all connected clients.
+
|Emits a <code>$message</code> to all connected clients. Invocations of this function are equivalent to <code>ws:send($message, ws:ids())</code>. See [[#ws:send|ws:send]] for more details on the message handling.
 +
|}
 +
 
 +
==ws:eval==
 +
 
 +
{| width='100%'
 +
|-
 +
| width='120' | '''Signatures'''
 +
|{{Func|ws:eval|$query as xs:anyAtomicItem|xs:string}}<br />{{Func|ws:eval|$query as xs:anyAtomicItem, $bindings as map(*)?|xs:string}}<br />{{Func|ws:eval|$query as xs:anyAtomicItem, $bindings as map(*)?, $options as map(*)?|xs:string}}<br />
 +
|-
 +
| '''Summary'''
 +
|Schedules the evaluation of the supplied {{Code|$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|$bindings}} (see {{Function|XQuery|xquery:eval}} for more details). The following {{Code|$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|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.
 +
Query scheduling is recommendable if the immediate query execution might be too time consuming and lead to a timeout.
 +
|-
 +
| '''Errors'''
 +
|{{Error|overflow|#Errors}} Query execution is rejected, because too many jobs are queued or being executed. <br/>{{Error|id|#Errors}} The specified id is invalid or has already been assigned.
 +
|-
 +
| '''Examples'''
 +
|
 +
* Schedule a second query that will notify the client 10 seconds later that a message was processed:
 +
<syntaxhighlight lang="xquery">
 +
declare
 +
  %ws:message('/tasks', '{$message}')
 +
function local:message($message) {
 +
  ws:eval('prof:sleep(10000), "Your message has been processed."')
 +
};
 +
</syntaxhighlight>
 
|}
 
|}
  
==ws:id==
+
=WebSocket Attributes=
 +
 
 +
==ws:get==
  
 
{| width='100%'
 
{| width='100%'
 
|-
 
|-
 
| width='120' | '''Signatures'''
 
| width='120' | '''Signatures'''
|{{Func|ws:id||xs:string}}
+
|{{Func|ws:get|$id as xs:string, $name as xs:string|item()*}}<br/>{{Func|ws:get|$id as xs:string, $name as xs:string, $default as item()*|item()*}}
 
|-
 
|-
 
| '''Summary'''
 
| '''Summary'''
|Returns the ID of the current WebSocket client.
+
|Returns the value of an attribute with the specified {{Code|$name}} from the WebSocket with the specified {{Code|$id}}. If the attribute is unknown, an empty sequence or the optionally specified {{Code|$default}} value will be returned instead.
 +
|-
 +
| '''Errors'''
 +
|{{Error|not-found|#Errors}} No WebSocket with the specified id exists.
 
|}
 
|}
  
==ws:ids==
+
==ws:set==
  
 
{| width='100%'
 
{| width='100%'
 
|-
 
|-
 
| width='120' | '''Signatures'''
 
| width='120' | '''Signatures'''
|{{Func|ws:ids||xs:string*}}
+
|{{Func|ws:set|$id as xs:string, $name as xs:string, $value as item()*|empty-sequence()}}
 
|-
 
|-
 
| '''Summary'''
 
| '''Summary'''
|Returns the ids of all currently registered WebSocket client.
+
|Returns the specified {{Code|value}} of the attribute with the specified {{Code|$name}} from the WebSocket with the specified {{Mono|$id}}.
 +
|-
 +
| '''Errors'''
 +
|{{Error|not-found|#Errors}} No WebSocket with the specified id exists.<br>{{Error|set|#Errors}} The supplied value cannot be materialized.
 
|}
 
|}
  
==ws:path==
+
==ws:delete==
  
 
{| width='100%'
 
{| width='100%'
 
|-
 
|-
 
| width='120' | '''Signatures'''
 
| width='120' | '''Signatures'''
|{{Func|ws:path||xs:string}}<br>{{Func|ws:path|$id as xs:string|xs:string}}
+
|{{Func|ws:delete|$id as xs:string, $name as xs:string|empty-sequence()}}
 
|-
 
|-
 
| '''Summary'''
 
| '''Summary'''
|Returns the path of the current WebSocket client, or the client with the specified {{Code|$id}}.
+
|Deletes an attribute with the specified {{Code|$name}} from the WebSocket with the specified {{Mono|$id}}.
 +
|-
 +
| '''Errors'''
 +
|{{Error|not-found|#Errors}} No WebSocket with the specified id exists.
 
|}
 
|}
  
Line 82: Line 176:
 
==Example 1==
 
==Example 1==
  
<pre class="brush:xquery">
+
<syntaxhighlight lang="xquery">
(: Import the WebSocket module :)
+
import module namespace ws = "http://basex.org/modules/ws";
import module namespace ws = "http://basex.org/modules/Websocket";
 
  
 
declare
 
declare
   %ws:connect("/")
+
   %ws:connect('/')
function local:connect(
+
function local:connect() as empty-sequence() {
) as empty-sequence() {
+
   let $id := ws:id()
   let $client-id := ws:id()
+
   let $message := json:serialize(map {
   let $client-path := ws:path()
+
     'type': 'Connect',
  let $response := json:serialize(
+
    'id': $id
     <json type="object">
+
  })
      <messageType>UserConnected</messageType>
+
   return ws:broadcast($message)
      <clientId>{$client-id}</clientId>
 
      <clientPath>{$client-path}</clientPath>
 
    </json>
 
  )
 
   return ws:broadcast($response)
 
 
};
 
};
</pre>
+
</syntaxhighlight>
  
```Explanation:```
+
'''Explanation:'''
  
* First of all: include the websocket module
+
* The function has a <code>%ws:connect</code> annotation. It gets called if a client successfully creates a WebSocket connection to the path <code>/</code> (check out [[WebSockets]] for further information).
* The <code>$ws:connect("/")</code> annotation gets called if a client successfully creates a websocket to the path "/" (checkout [[WebSockets]] for further information).
+
* A JSON response is generated, which contains the new client id and a <code>Connect</code> string.
* Get the <code>client-id</code> and the <code>client-path</code> with <code>ws:id()</code> and <code>ws:path()</code>
+
* This response will be sent to all other connected clients.
* Create a json-result
 
* Broadcast the result to all connected clients without the calling client
 
  
 
==Example 2==
 
==Example 2==
  
<pre class="brush:xquery">
+
<syntaxhighlight lang="xquery">
(: Import the Websockets module :)
+
import module namespace ws = "http://basex.org/modules/ws";
import module namespace ws = "http://basex.org/modules/Websocket";
 
  
 
declare
 
declare
   %ws:message("/", "{$message}")
+
   %ws:message('/', '{$message}')
 
function local:message(
 
function local:message(
   $message as xs:string
+
   $message as xs:string
 
) as empty-sequence() {
 
) as empty-sequence() {
   let $client-ids := ws:ids()
+
   let $message := json:serialize(map { 'message': $message })
  let $fist-client-id := fn:head($client-ids)
+
   return ws:emit($message)
  let $send-to-id := ws:send($message, $first-client-id)
 
  let $path-first-client := ws:path($first-client-id)
 
  let $response := json:serialize(
 
    <json type="object">
 
      <messageType>PathFirstClient</messageType>
 
      <path>{ $path-first-client }</path>
 
    </json>
 
  )  
 
   return ws:emit($response)
 
 
};
 
};
</pre>
+
</syntaxhighlight>
 +
 
 +
'''Explanation:'''
 +
 
 +
* The function has a <code>%ws:message</code> 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=
 +
 
 +
{| class="wikitable" width="100%"
 +
! width="110"|Code
 +
|Description
 +
|-
 +
|{{Code|set}}
 +
|The supplied value cannot be materialized.
 +
|-
 +
|{{Code|not-found}}
 +
|No WebSocket with the specified id exists.
 +
|}
 +
 
 +
=Changelog=
 +
 
 +
;Version 9.2
  
```Explanation:```
+
* Added: [[#ws:eval|ws:eval]]
  
* First of all, import the websocket module
+
This module was introduced with Version 9.1.
* The annotation <code>$ws:message("/",{$message}")</code> gets called if a message arrives at the server (checkout [[WebSockets]] for further information).
 
* With <code>ws:ids()</code> you will get the ids of all connected clients.
 
* The function <code>ws:send($message,$first-client-id)</code> sends the <code>$message</code> to the client with the id <code>$first-client-id</code>
 
* <code>ws:path($first-client-id)</code> returns the path of the client with the id <code>$first-client-id</code>
 
* To emit a message to all connected clients you call <code>ws:emit($response)</code>
 

Latest revision as of 15:43, 27 February 2020

This XQuery Module contains functions for accessing specific WebSocket functions. This module is mainly useful in the context of WebSockets.

Conventions[edit]

  • 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 the ws 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[edit]

ws:id[edit]

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[edit]

Signatures ws:ids() as xs:string*
Summary Returns the ids of all currently registered WebSockets.

ws:path[edit]

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[edit]

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[edit]

ws:send[edit]

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:
  • Items of type xs:base64Binary and xs:hexBinary will be transmitted as binary messages.
  • Function items (maps, arrays) will be serialized as JSON and transmitted as string messages.
  • All other items will be serialized with the default serialization options and transmitted as string messages.

ws:broadcast[edit]

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[edit]

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[edit]

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:
  • base-uri: sets the base-uri property for the query. This URI will be used when resolving relative URIs, such as with fn:doc.
  • id: sets a custom job id. The id must not start with the standard job prefix, and it can only be assigned if no job with the same name exists.

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
  • Schedule a second query that will notify the client 10 seconds later that a message was processed:
declare
  %ws:message('/tasks', '{$message}')
function local:message($message) {
  ws:eval('prof:sleep(10000), "Your message has been processed."')
};

WebSocket Attributes[edit]

ws:get[edit]

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[edit]

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[edit]

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[edit]

Example 1[edit]

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[edit]

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[edit]

Code Description
set The supplied value cannot be materialized.
not-found No WebSocket with the specified id exists.

Changelog[edit]

Version 9.2

This module was introduced with Version 9.1.