|By Lahlali Issam||
|December 7, 2011 08:45 AM EST||
According to the MVC definition from wikipedia:
"Model View Controller (MVC) pattern creates applications that separate the different aspects of the application (input logic, business logic, and UI logic), while providing a loose coupling between these elements."
The question is which one is the best to use?
As with any debate like that, there's no unique solution as it depends on many factors. In this article we try using JavaDepend to discover PureMVC in-depth, and talk about the main difference between it and the other variants.
PureMVC was popularized first by Flex and Flash developers, but it was ported after to many other langugages.The following GWT sample uses the Java PureMVC framework. Let's analyze it to explore PureMVC concepts.
PureMVC Basic Concepts
Here's the structure of the project
This structure shows the main PureMVC concepts:
- Facade: Initializes and caches the core actors (model, view, and controller) and provides a single place to access all of them.
- Proxies: Expose an API for manipulating the data model ,including data retrieved from remote services.
- Mediators: The view communicate with their Mediators using Events and exposing some properties for the concrete Mediator to inspect or manage. A Mediator connects a View Component with its data and communicates with the rest of the system on its behalf.
- Commands: A Command may retrieve and interact with Proxies, communicate with Mediators, or execute other Commands. Commands are often used to orchestrate complex or system-wide activities such as application startup and shutdown.
The PureMVC best practices encourage developers to put each actor into a specific namespace to modularize the application better.
Here's the graph representing the communication between all namespaces.
There's no dependency cycle as it's well layered, which makes it very clear and simple to understand. The matrix gives us more details about dependency weight between all the namespaces.
The PureMVC Glue
To go deep inside the sample let's discover the dependency graph between all classes:
What's interesting in this dependency graph is that almost all classes uses INotification.
PureMVC uses the publish-subscribe pattern to communicate between all actors (Model,View,Controler), and for this reason INotification is mainly used. To check that let's discover the most popular types and for that we can use the TypeRank metric.
SELECT TOP 100 TYPES ORDER BY TypeRank DESC, TypeCa DESC
The three most popular types concern the notification mechanism, the proof that this concept is the glue of the PureMVC framework. Almost all communication between actors use notification, which makes them less coupled.
Publish–subscribe is a messaging pattern where senders of messages, called publishers, do not program the messages to be sent directly to specific receivers, called subscribers. Published messages are characterized into classes, without knowledge of what, if any, subscribers there may be. Subscribers express interest in one or more classes, and only receive messages that are of interest, without knowledge of what, if any, publishers there are.
This allows asynchronous, event-driven communications between the actors of the system, and also promotes a loose coupling between those actors, since the subscriber never needs to have direct knowledge of the publisher.
For our sample we can search for all classes using Notifier class to notify other actors.
SELECT METHODS FROM JARS "PureMVC" WHERE IsDirectlyUsing
Almost all actors: Mediators,Commands and proxies use the notification mechanism to communicate with each others.
Here's a concrete example of adding a new user from view.
In this sample the mediator ask the proxy to add a user and afterward sends a notification to inform all other components that a user was added.
What's interesting to note here is that the mediator communicates directly with the proxy. In PureMVC, proxies can't act as subscribers, and can only publish notification.
Inside PureMVC Concepts
Facade is singleton
If we search where the facade is instantiated
SELECT METHODS WHERE DepthOfCreateA
"org.puremvc.java.multicore.patterns.facade.Facade" == 1
Only one static method getInstance instantiates it, but this method has one parameter so we can create many facades. Each component has its own singleton facade identified by a name, and that's why we talk about PureMVC MultiCore.
SELECT METHODS WHERE IsDirectlyUsedBy
The facade initializes all other actors.
Facade and notification:
The facade caches all actors, and when a notification is published, the facade notifies all observers.
Let's search for all methods used by DeleteUserCommand, the command responsible for deleting a user.
SELECT METHODS WHERE IsDirectlyUsedBy
The command doesn't communicate directly with other components, except for the proxy as we observed earlier.
SELECT METHODS WHERE IsDirectlyUsedBy
Like Commands, mediators mainly use notifications to interact with other classes except for proxies.
The question that makes a difference using PureMVC and gives us three more other variants is: Who communicates with the proxy?
Here are three ways developers are using PureMVC:
1. Only commands use proxies: We suppose that only commands have to abstract the logic of the application. This solution makes the code more reusable, for example, deleteuser could be used by many classes, and if this logic exists in a mediator instead of a command, we have to duplicate the code if another mediator need to also delete a user.
2. Commands and mediators use the proxy: For our sample it's what happens.The AddUser is invoked from a mediator and the deleteuser from a command.
3. Only Mediators use proxies and commands are used only for startup: Some developers prefer not to use Commands and use only Mediators, to not add more classes and maybe more complexity to the code.
The main difference between PureMVC and the other variants is the way that all actors communicate with each others. PureMVC chooses the asynchronous and the less-coupled solution.
When people aren’t talking about VMs and containers, they’re talking about serverless architecture. Serverless is about no maintenance. It means you are not worried about low-level infrastructural and operational details. An event-driven serverless platform is a great use case for IoT. In his session at @ThingsExpo, Animesh Singh, an STSM and Lead for IBM Cloud Platform and Infrastructure, will detail how to build a distributed serverless, polyglot, microservices framework using open source tec...
Jun. 27, 2016 08:30 PM EDT Reads: 324
IoT offers a value of almost $4 trillion to the manufacturing industry through platforms that can improve margins, optimize operations & drive high performance work teams. By using IoT technologies as a foundation, manufacturing customers are integrating worker safety with manufacturing systems, driving deep collaboration and utilizing analytics to exponentially increased per-unit margins. However, as Benoit Lheureux, the VP for Research at Gartner points out, “IoT project implementers often ...
Jun. 27, 2016 07:45 PM EDT Reads: 346
Basho Technologies has announced the latest release of Basho Riak TS, version 1.3. Riak TS is an enterprise-grade NoSQL database optimized for Internet of Things (IoT). The open source version enables developers to download the software for free and use it in production as well as make contributions to the code and develop applications around Riak TS. Enhancements to Riak TS make it quick, easy and cost-effective to spin up an instance to test new ideas and build IoT applications. In addition to...
Jun. 27, 2016 05:15 PM EDT Reads: 356
Presidio has received the 2015 EMC Partner Services Quality Award from EMC Corporation for achieving outstanding service excellence and customer satisfaction as measured by the EMC Partner Services Quality (PSQ) program. Presidio was also honored as the 2015 EMC Americas Marketing Excellence Partner of the Year and 2015 Mid-Market East Partner of the Year. The EMC PSQ program is a project-specific survey program designed for partners with Service Partner designations to solicit customer feedbac...
Jun. 27, 2016 03:15 PM EDT Reads: 351
Machine Learning helps make complex systems more efficient. By applying advanced Machine Learning techniques such as Cognitive Fingerprinting, wind project operators can utilize these tools to learn from collected data, detect regular patterns, and optimize their own operations. In his session at 18th Cloud Expo, Stuart Gillen, Director of Business Development at SparkCognition, discussed how research has demonstrated the value of Machine Learning in delivering next generation analytics to imp...
Jun. 27, 2016 03:00 PM EDT Reads: 760
In his general session at 18th Cloud Expo, Lee Atchison, Principal Cloud Architect and Advocate at New Relic, discussed cloud as a ‘better data center’ and how it adds new capacity (faster) and improves application availability (redundancy). The cloud is a ‘Dynamic Tool for Dynamic Apps’ and resource allocation is an integral part of your application architecture, so use only the resources you need and allocate /de-allocate resources on the fly.
Jun. 27, 2016 03:00 PM EDT Reads: 1,159
It is one thing to build single industrial IoT applications, but what will it take to build the Smart Cities and truly society changing applications of the future? The technology won’t be the problem, it will be the number of parties that need to work together and be aligned in their motivation to succeed. In his Day 2 Keynote at @ThingsExpo, Henrik Kenani Dahlgren, Portfolio Marketing Manager at Ericsson, discussed how to plan to cooperate, partner, and form lasting all-star teams to change t...
Jun. 27, 2016 02:45 PM EDT Reads: 1,232
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life sett...
Jun. 27, 2016 02:30 PM EDT Reads: 1,237
There are several IoTs: the Industrial Internet, Consumer Wearables, Wearables and Healthcare, Supply Chains, and the movement toward Smart Grids, Cities, Regions, and Nations. There are competing communications standards every step of the way, a bewildering array of sensors and devices, and an entire world of competing data analytics platforms. To some this appears to be chaos. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, Bradley Holt, Developer Advocate a...
Jun. 27, 2016 12:00 PM EDT Reads: 847
Connected devices and the industrial internet are growing exponentially every year with Cisco expecting 50 billion devices to be in operation by 2020. In this period of growth, location-based insights are becoming invaluable to many businesses as they adopt new connected technologies. Knowing when and where these devices connect from is critical for a number of scenarios in supply chain management, disaster management, emergency response, M2M, location marketing and more. In his session at @Th...
Jun. 27, 2016 10:00 AM EDT Reads: 1,055
The cloud market growth today is largely in public clouds. While there is a lot of spend in IT departments in virtualization, these aren’t yet translating into a true “cloud” experience within the enterprise. What is stopping the growth of the “private cloud” market? In his general session at 18th Cloud Expo, Nara Rajagopalan, CEO of Accelerite, explored the challenges in deploying, managing, and getting adoption for a private cloud within an enterprise. What are the key differences between wh...
Jun. 27, 2016 09:30 AM EDT Reads: 899
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, wh...
Jun. 27, 2016 07:30 AM EDT Reads: 1,076
Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is expected in the amount of information being processed, managed, analyzed, and acted upon by enterprise IT. This amazing is not part of some distant future - it is happening today. One report shows a 650% increase in enterprise data by 2020. Other estimates are even higher....
Jun. 26, 2016 05:00 PM EDT Reads: 1,326
SYS-CON Events announced today that Bsquare has been named “Silver Sponsor” of SYS-CON's @ThingsExpo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. For more than two decades, Bsquare has helped its customers extract business value from a broad array of physical assets by making them intelligent, connecting them, and using the data they generate to optimize business processes.
Jun. 26, 2016 05:00 PM EDT Reads: 1,244
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices - comp...
Jun. 26, 2016 04:00 PM EDT Reads: 1,299
19th Cloud Expo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy. Meanwhile, 94% of enterpri...
Jun. 26, 2016 04:00 PM EDT Reads: 1,367
The 19th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Digital Transformation, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportuni...
Jun. 26, 2016 12:00 PM EDT Reads: 1,315
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with the 19th International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world and ThingsExpo Silicon Valley Call for Papers is now open.
Jun. 26, 2016 12:00 PM EDT Reads: 1,153
There is little doubt that Big Data solutions will have an increasing role in the Enterprise IT mainstream over time. Big Data at Cloud Expo - to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA - has announced its Call for Papers is open. Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is...
Jun. 26, 2016 12:00 PM EDT Reads: 1,376
Cognitive Computing is becoming the foundation for a new generation of solutions that have the potential to transform business. Unlike traditional approaches to building solutions, a cognitive computing approach allows the data to help determine the way applications are designed. This contrasts with conventional software development that begins with defining logic based on the current way a business operates. In her session at 18th Cloud Expo, Judith S. Hurwitz, President and CEO of Hurwitz & ...
Jun. 25, 2016 03:00 PM EDT Reads: 1,652