ConnectionManager class

• Usual additions
• ConnectionManager class
• daoBuilder function
• User class
• getUser function
• getLocale function

The ConnectionManager object will provide the connections (and transactions) for each data store inside the business object instances during data portal actions. The class must inherit the ConnectionManagerBase class and override the methods of the base class:

• openConnection( dataSource, callback )
• closeConnection( dataSource, connection, callback )
• beginTransaction( dataSource, callback )
• commitTransaction( dataSource, connection, callback )
• rollbackTransaction( dataSource, connection, callback )

The callback function is valid for asynchronous models only, synchronous models expect a return value.

The above functions have the following arguments:

• dataSource
  The name of the data source.
• connection
  The current connection object.
• callback
  For asynchronous objects: A function with callback(err, result) signature, where err is the eventual error and result is a connection object in openConnection() and beginTransaction() functions.
• returns
  For synchronous objects: The connection object in openConnection() and beginTransaction() functions.

The code below shows a sample implementation for a MySQL database:

'use strict';

var util = require('util');
var mysql = require('mysql');
var bo = require('business-objects');
var app = require('../server.js');

var pool = mysql.createPool({
  host     : app.config.dataSources.mysql.host,
  port     : app.config.dataSources.mysql.port,
  database : app.config.dataSources.mysql.database,
  user     : app.config.dataSources.mysql.username,
  password : app.config.dataSources.mysql.password,
  multipleStatements: true
});

var ConnectionManagerBase = bo.dataAccess.ConnectionManagerBase;

// Connection manager constructor.
var ConnectionManager = function() {
  ConnectionManager.super_.call(this);
};
util.inherits(ConnectionManager, ConnectionManagerBase);

// Open connection.
ConnectionManager.prototype.openConnection = function (dataSource, callback) {
  pool.getConnection(function (err, connection) {
    if (err)
      callback(err);
    else
      callback(null, connection);
  });
};

// Close connection.
ConnectionManager.prototype.closeConnection = function (dataSource, connection, callback) {
  connection.release();
  callback();
};

// Begin transaction.
ConnectionManager.prototype.beginTransaction = function (dataSource, callback) {
  this.openConnection(dataSource, function (err, connection) {
    if (err)
      callback(err);
    else
      connection.beginTransaction(function (err) {
        if (err)
          callback(err);
        else
          callback(null, connection);
      })
  });
};

// Commit transaction.
ConnectionManager.prototype.commitTransaction = function (dataSource, connection, callback) {
  var self = this;
  connection.commit(function (err) {
    if (err)
      self.rollbackTransaction(dataSource, connection, callback);
    else
      self.closeConnection(dataSource, connection, callback);
  });
};

// Rollback transaction.
ConnectionManager.prototype.rollbackTransaction = function (dataSource, connection, callback) {
  var self = this;
  connection.rollback(function () {
    self.closeConnection(dataSource, connection, callback);
  });
};

module.exports = ConnectionManager;

If the projects uses several databases, it can be handled using the switch(dataSource) { } statement.