Difference between revisions of "Client Module"

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| '''Summary'''
 
| '''Summary'''
| This function executes a command and returns the result as string. The parameter {{Code|$id}} contains the session id returned by [[Client Module#client:connect|client:connect]]. The {{Code|$command}} represents the [[Commands#Basics|command string]], which will be executed by the server.
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| This function executes a [[Commands|command]] and returns the result as string. The parameter {{Code|$id}} contains the session id returned by [[Client Module#client:connect|client:connect]]. The {{Code|$command}} argument represents a single command, which will be executed by the server.
 
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|'''Errors'''
 
|'''Errors'''

Revision as of 18:58, 23 August 2012

This XQuery Module contains functions to access remote BaseX server instances from XQuery. With this module, you can on the one hand execute database commands and on the other hand evaluate queries, the results of which are returned as XDM sequences.

Conventions

All functions in this module are assigned to the http://basex.org/modules/client namespace, which is statically bound to the client prefix.
All errors are assigned to the http://basex.org/errors namespace, which is statically bound to the bxerr prefix.

Functions

client:connect

Signatures client:connect($host as xs:string, $port as xs:integer, $user as xs:string, $password as xs:string) as xs:anyURI
Summary This function establishes a connection to a remote BaseX server, creates a new client session, and returns a session id. The parameter $host is the name of the database server, $port specifies the server port, and $user and $password represent the login data.
Errors BXCL0001: an error occurs while creating the session (possible reasons: server not available, access denied).

client:execute

Signatures client:execute($id as xs:anyURI, $command as xs:string) as xs:string
Summary This function executes a command and returns the result as string. The parameter $id contains the session id returned by client:connect. The $command argument represents a single command, which will be executed by the server.
Errors BXCL0003: an I/O error occurs while transferring data from or to the server.
BXCL0004: an error occurs while executing a command.
Examples The following query creates a new database TEST on a remote BaseX server:
client:connect('basex.server.org', 8080, 'admin', 'admin') !
  client:execute(., 'create database TEST')

client:info

Template:Mark

Signatures client:info($id as xs:anyURI) as xs:string
Summary This function returns an information string, created by a previous call of client:execute. $id specifies the session id.

client:query

Signatures client:query($id as xs:anyURI, $query as xs:string) as item()*
client:query($id as xs:anyURI, $query as xs:string, $bindings as map(*)) as item()*
Summary Evaluates a query and returns the result as sequence. The parameter $id contains the session id returned by client:connect, and $query represents the query string, which will be evaluated by the server.
Variables and the context item can be declared via $bindings. The specified keys must be QNames or strings, the values can be arbitrary items:
  • variables specified as QNames will be directly interpreted as variable name.
  • variables specified as xs:string may be prefixed with a dollar sign. Namespace can be specified using the Clark Notation. If the specified string is empty, the value will be bound to the context item.
Errors BXCL0003: an I/O error occurs while transferring data from or to the server.
BXCL0005: an error occurs while evaluating a query, and if the original error cannot be extracted from the returned error string.
Examples The following query sends a query on a local server instance, binds the integer 123 to the variable $n and returns 246:
let $c := client:connect('localhost', 1984, 'admin', 'admin')
return client:query($c, "$n * 2", map{ 'n' := 123 })

The following query performs a query on a first server, the results of which are passed on to a second server:

let $c1 := client:connect('basex1.server.org', 8080, 'jack', 'C0S19tt2X')
let $c2 := client:connect('basex2.server.org', 8080, 'john', '465wFHe26')
for $it in client:query($c1, '1 to 10')
return client:query($c2, $it || '* 2')

client:close

Signatures client:close($id as xs:anyURI) as empty-sequence()
Summary This function closes a client session. $id specifies the session id.
At the end of query execution, open sessions will be automatically closed.
Errors BXCL0003: an I/O error occurs while transferring data from or to the server.

Errors

Code Description
BXCL0001 An error occurred while creating a new session (possible reasons: server not available, access denied).
BXCL0002 The specified session is unknown, or has already been closed.
BXCL0003 An I/O error occurred while transferring data from or to the server.
BXCL0004 An error occurred while executing a command.
BXCL0005 An error occurred while evaluating a query. Will only be raised if the XQuery error cannot be extracted from the returned error string.

Changelog

Version 7.4

The module was introduced with Version 7.3.