Add transaction

index.js

@@ -12,3 +12,5 @@ var commonTest = './test/common_test';
 Object.defineProperty(exports, 'test', {
   get: function() {return require(commonTest);}
 });
+
+exports.Transaction = require('loopback-connector').Transaction;

lib/dao.js

@@ -2324,3 +2324,8 @@ jutil.mixin(DataAccessObject, Inclusion);
  * Add 'relation'
  */
 jutil.mixin(DataAccessObject, Relation);
+
+/*
+ * Add 'transaction'
+ */
+jutil.mixin(DataAccessObject, require('./transaction'));

lib/transaction.js

@@ -0,0 +1,55 @@
+var Transaction = require('loopback-connector').Transaction;
+
+module.exports = TransactionMixin;
+
+function TransactionMixin() {
+}
+
+/**
+ * Begin a new transaction
+ * @param {Object|String} [options] Options can be one of the forms:
+ * - Object: {isolationLevel: '...', timeout: 1000}
+ * - String: isolationLevel
+ *
+ * Valid values of `isolationLevel` are:
+ *
+ * - Transaction.READ_COMMITTED = 'READ COMMITTED'; // default
+ * - Transaction.READ_UNCOMMITTED = 'READ UNCOMMITTED';
+ * - Transaction.SERIALIZABLE = 'SERIALIZABLE';
+ * - Transaction.REPEATABLE_READ = 'REPEATABLE READ';
+ *
+ * @param {Function} cb Callback function. It calls back with (err, transaction).
+ * To pass the transaction context to one of the CRUD methods, use the `options`
+ * argument with `transaction` property, for example,
+ *
+ * ```js
+ *
+ * MyModel.beginTransaction('READ COMMITTED', function(err, tx) {
+ *   MyModel.create({x: 1, y: 'a'}, {transaction: tx}, function(err, inst) {
+ *     MyModel.find({x: 1}, {transaction: tx}, function(err, results) {
+ *       // ...
+ *       tx.commit(function(err) {...});
+ *     });
+ *   });
+ * });
+ * ```
+ *
+ * The transaction can be committed or rolled back. If timeout happens, the
+ * transaction will be rolled back. Please note a transaction is typically
+ * associated with a pooled connection. Committing or rolling back a transaction
+ * will release the connection back to the pool.
+ *
+ */
+TransactionMixin.beginTransaction = function(options, cb) {
+  if (Transaction) {
+    var connector = this.getConnector();
+    Transaction.begin(connector, options, cb);
+  } else {
+    process.nextTick(function() {
+      var err = new Error('Transaction is not supported');
+      cb(err);
+    });
+  }
+};
+
+