simple-basex

simple-basex - Node.JS client interface to the BaseX XML database

simple-basex attempts to implement a simple to use client interface to the BaseX XML database. It deviates from the client API proposed in the BaseX documentation in particular with respect to the bound query interface.

Installation

simple-basex is self contained and uses only core Node.JS functionality. It can be installed using npm:

npm install basex

A simple test script is provided which requires a BaseX server running on the local machine. By default, the username "admin" and the password "admin" are used to access BaseX. See "Environment Variables" below if you need to use different credentials.

Usage

simple-basex implements a client interface that is simple to use in the asynchronous context of Node.JS. Commands can be sent to the database server without waiting for responses. Responses can either be collected by callbacks, or by the way of events emitted by the client session object.

An example might look like this:

var basex = require('simple-basex');
var s = new basex.Session();
s.execute('open mydatabase');
s.query('//product', function (err, result) {
    if (err) throw err;
    console.log('product', result);
});

All interaction with BaseX is mediated through a Session object which needs to be allocated using the new operator. Database commands can be executed through the execute function. Queries are typically sent using the query function, which also supports bound variables.

Prepared query execution

simple-basex supports prepared query execution in BaseX versions 7.6.1 beta and later. In this mode, a query is prepared and can then be executed multiple times with different variable bindings:

var basex = require('./index');
var s = new basex.Session();

var query = s.query('<foo bar="{$bar}"/>');
query.on('result', function (result) {
    console.log('query event', result);
});
query.execute({ bar: 1 });
query.execute({ bar: 2 }, function (err, result) {
    console.log('query result', result);
    s.execute('exit');
});

Environment variables

The authentication credentials used to log in to the BaseX server can be supplied to the Session constructor. If no explicit credentials are provided, the built-in defaults of simple-basex can be overridden using the following environment variables:

BASEX_HOST

Sets the host on which the BaseX server runs, defaults to localhost.

BASEX_PORT

Port number of the BaseX server, defaults to 1984.

BASEX_USERNAME

User name, defaults to admin.

BASEX_PASSWORD

Password, defaults to admin.

API functions

new Session(options)

Creates a new database client session. options can be passed to override the default and environment credentials. It needs to be an object with any of the host, port, username or password keys set to the desired value.

The returned session object handles the context for all database interactions.

The session object is an EventEmitter. When a connection error is encountered by the client, it is forwarded as 'connectionError' event on the session object. This can be used to implement automatic database reconnection for long running server processes.

session.execute(command, [handler])

Execute the command on the database server. Upon completion, the handler callback is invoked with two arguments. The first argument is either null or an Error object if an error occured executing the command. The second argument is an object with reply and info keys which contain the data that the command yielded and the diagnostic information for the command execution, respectively. If no handler is provided, an 'error' or 'result' event will be emitted by the Session object.

session.query(query, [bindings], [handler])

Execute the query, which needs to contain an XQuery string. bindings can contain variable bindings which need to be passed as object. The data types of the bound variables will be automatically determined from the value types in the bindings object.

handler is an optional handler with the conventional (err, data) signature. err will be an Error object if an error occured during query execution. data will contain the result string. Query diagnostics are not currently returned for bound query execution.

When both bindings and handler are unspecified, the query is prepared, but not executed, and a query object is returned. That object can then be used to execute the query. With BaseX version 7.6.1 beta or later, the query can be executed multiple times, with different variable bindings.

query.execute([bindings], [handler])

Execute the previously prepared query. bindings specify variable bindings as a map, handler is the callback to call. If no handler is specified, an 'error' or 'result' event will be emitted on the query when execution is complete.