Replace serializer with data mapper (#10)

Resolves #7: Support custom mappings of session object to a database record.

README.md

@@ -63,8 +63,8 @@ parameters:
   Aerospike db. If not specified, the ttl will be determined based on the
   `maxAge` of the session cookie, if any. Set `ttl` to zero to disable usage of
   ttl. However, note that a default ttl at the namespace level might still apply.
-* `serializer` - A custom serializer to convert session objects to/from a
-  format suitable for storage in an Aerospike record. By default the `JSON`
+* `mapper` - A custom data mapper to convert session objects to/from a
+  format suitable for storage in an Aerospike record. By default, the `JSON`
   module is used to serialize session objects to/from JSON format.
 
 Additional options are passed on to the Aerospike client when creating a new

lib/aerospike_store.js

@@ -17,6 +17,7 @@
 'use strict'
 
 const Aerospike = require('aerospike')
+const DataMapper = require('./data_mapper')
 
 const debug = require('debug')('session:aerospike')
 const util = require('util')
@@ -42,7 +43,11 @@ module.exports = function (session) {
     this.as_namespace = options.namespace || 'test'
     this.as_set = options.set || 'express-session'
     this.ttl = options.ttl
-    this.serializer = options.serializer || JSON
+    this.mapper = options.mapper || new DataMapper()
+
+    if (options.serializer) {
+      throw new Error('The `serializer` option is no longer supported - supply a custom data mapper instead.')
+    }
 
     if (options.client) {
       this.client = options.client
@@ -120,27 +125,22 @@ module.exports = function (session) {
   AerospikeStore.prototype.get = function (sid, callback) {
     const key = this._key(sid)
     debug('GET "%s"', sid)
-    this.client.get(key, (err, record) => {
-      if (err) {
-        switch (err.code) {
+    this.client.get(key, (error, record) => {
+      if (error) {
+        switch (error.code) {
           case Aerospike.status.AEROSPIKE_ERR_RECORD_NOT_FOUND:
             return callback()
           default:
-            return callback(err)
+            return callback(error)
         }
       }
 
-      const bins = record.bins
-      const sessionBin = bins.session
-      if (!sessionBin) {
-        return callback()
-      }
-
       try {
-        const session = this.serializer.parse(sessionBin)
+        const bins = record.bins
+        const session = this.mapper.fromRecord(bins)
         return callback(null, session)
-      } catch (err) {
-        return callback(err)
+      } catch (error) {
+        return callback(error)
       }
     })
   }
@@ -169,7 +169,7 @@ module.exports = function (session) {
   AerospikeStore.prototype.set = function (sid, session, callback) {
     try {
       const key = this._key(sid)
-      const bins = { session: this.serializer.stringify(session) }
+      const bins = this.mapper.toRecord(session)
       const meta = { ttl: this._ttl(session) }
       debug('PUT "%s", ttl: %s', sid, meta.ttl)
       this.client.put(key, bins, meta, error => callback(error))

lib/data_mapper.js

@@ -0,0 +1,45 @@
+// *****************************************************************************
+// Copyright 2016-2017 Aerospike, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License")
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// *****************************************************************************
+
+'use strict'
+
+class DataMapper {
+  /**
+   * Converts a session object into a database record.
+   *
+   * @param {Object} session - session object
+   * @returns {Object} Aerospike database record
+   */
+  toRecord (session) {
+    return {
+      session: JSON.stringify(session)
+    }
+  }
+
+  /**
+   * Converts a database record into a session object.
+   *
+   * @param {Object} record - Aerospike record bins
+   * @param {Object} session object
+   */
+  fromRecord (record) {
+    const sessionBin = record.session
+    if (!sessionBin) return null
+    return JSON.parse(sessionBin)
+  }
+}
+
+module.exports = DataMapper

test/aerospike_store_test.js

@@ -129,21 +129,28 @@ test('failed connection', function (t) {
 })
 
 test('serializer', function (t) {
-  const serializer = {
-    stringify: (value, replacer, space) => 'XXX' + JSON.stringify(value, replacer, space),
-    parse: str => {
-      t.ok(str.match(/^XXX/))
-      return JSON.parse(str.substring(3))
-    }
+  const fn = function () {
+    const options = { serializer: 'foo' }
+    const store = new AerospikeStore(options)
+    store.close(false)
+  }
+  t.throws(fn, 'serializer', 'Trying to set `serializer` should raise an error')
+  t.end()
+})
+
+test('mapper', function (t) {
+  const mapper = {
+    toRecord: session => session,
+    fromRecord: bins => bins
   }
-  t.equal(serializer.stringify('UnitTest'), 'XXX"UnitTest"')
-  t.equal(serializer.parse(serializer.stringify('UnitTest')), 'UnitTest')
+  t.deepEqual(mapper.toRecord({ name: 'jan' }), { name: 'jan' })
+  t.deepEqual(mapper.fromRecord({ name: 'jan' }), { name: 'jan' })
 
-  const store = new AerospikeStore({ serializer: serializer })
+  const store = new AerospikeStore({ mapper: mapper })
   return lifecycleTest(store, t)
 })
 
-test('serializer error', function (t) {
+test('mapper error', function (t) {
   const a = {}
   const b = {}
   // create circular reference to cause serialization error