Welcome!

Java Authors: Pat Romanski, Carmen Gonzalez, Liz McMillan, Yeshim Deniz, Yakov Fain

Related Topics: Java, SOA & WOA

Java: Article

Exploring PureMVC

Let's discover the main difference between PureMVC and the other variants

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."

But if we search for MVC frameworks we found many variants: MVC1, MVC2, MVC3, MVP, MVVM and PureMVC.

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
"org.puremvc.java.multicore.patterns.observer.Notifier"

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

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.

Facade Initialization:

SELECT METHODS WHERE IsDirectlyUsedBy
"org.puremvc.java.multicore.patterns.facade.Facade"

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.

Commands
Let's search for all methods used by DeleteUserCommand, the command responsible for deleting a user.

SELECT METHODS WHERE IsDirectlyUsedBy
"org.puremvc.java.multicore.demos.gwt.
employeeadmin.controller.DeleteUserCommand"

The command doesn't communicate directly with other components, except for the proxy as we observed earlier.

Mediators

SELECT METHODS WHERE IsDirectlyUsedBy 
"org.puremvc.java.multicore.demos.gwt.
employeeadmin.view.UserFormMediator"

Like Commands, mediators mainly use notifications to interact with other classes except for proxies.

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.

More Stories By Lahlali Issam

Lahlali Issam Lead Developer at JavaDepend, a tool to manage and understand complex Java code. With JavaDepend, software quality can be measured using Code Metrics, visualized using Graphs and Treemaps, and queried using CQL language, a SQL like to query the code base.

@ThingsExpo Stories
SYS-CON Events announced today that Matrix.org has been named “Silver Sponsor” of Internet of @ThingsExpo, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Matrix is an ambitious new open standard for open, distributed, real-time communication over IP. It defines a new approach for interoperable Instant Messaging and VoIP based on pragmatic HTTP APIs and WebRTC, and provides open source reference implementations to showcase and bootstrap the new standard. Our focus is on simplicity, security, and supporting the fullest feature set.
WebRTC defines no default signaling protocol, causing fragmentation between WebRTC silos. SIP and XMPP provide possibilities, but come with considerable complexity and are not designed for use in a web environment. In his session at Internet of @ThingsExpo, Matthew Hodgson, technical co-founder of the Matrix.org, will discuss how Matrix is a new non-profit Open Source Project that defines both a new HTTP-based standard for VoIP & IM signaling and provides reference implementations.

SUNNYVALE, Calif., Oct. 20, 2014 /PRNewswire/ -- Spansion Inc. (NYSE: CODE), a global leader in embedded systems, today added 96 new products to the Spansion® FM4 Family of flexible microcontrollers (MCUs). Based on the ARM® Cortex®-M4F core, the new MCUs boast a 200 MHz operating frequency and support a diverse set of on-chip peripherals for enhanced human machine interfaces (HMIs) and machine-to-machine (M2M) communications. The rich set of periphera...

SYS-CON Events announced today that Aria Systems, the recurring revenue expert, has been named "Bronze Sponsor" of SYS-CON's 15th International Cloud Expo®, which will take place on November 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Aria Systems helps leading businesses connect their customers with the products and services they love. Industry leaders like Pitney Bowes, Experian, AAA NCNU, VMware, HootSuite and many others choose Aria to power their recurring revenue business and deliver exceptional experiences to their customers.
The Internet of Things (IoT) is going to require a new way of thinking and of developing software for speed, security and innovation. This requires IT leaders to balance business as usual while anticipating for the next market and technology trends. Cloud provides the right IT asset portfolio to help today’s IT leaders manage the old and prepare for the new. Today the cloud conversation is evolving from private and public to hybrid. This session will provide use cases and insights to reinforce the value of the network in helping organizations to maximize their company’s cloud experience.
The Internet of Things (IoT) is making everything it touches smarter – smart devices, smart cars and smart cities. And lucky us, we’re just beginning to reap the benefits as we work toward a networked society. However, this technology-driven innovation is impacting more than just individuals. The IoT has an environmental impact as well, which brings us to the theme of this month’s #IoTuesday Twitter chat. The ability to remove inefficiencies through connected objects is driving change throughout every sector, including waste management. BigBelly Solar, located just outside of Boston, is trans...
SYS-CON Events announced today that Matrix.org has been named “Silver Sponsor” of Internet of @ThingsExpo, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Matrix is an ambitious new open standard for open, distributed, real-time communication over IP. It defines a new approach for interoperable Instant Messaging and VoIP based on pragmatic HTTP APIs and WebRTC, and provides open source reference implementations to showcase and bootstrap the new standard. Our focus is on simplicity, security, and supporting the fullest feature set.
Predicted by Gartner to add $1.9 trillion to the global economy by 2020, the Internet of Everything (IoE) is based on the idea that devices, systems and services will connect in simple, transparent ways, enabling seamless interactions among devices across brands and sectors. As this vision unfolds, it is clear that no single company can accomplish the level of interoperability required to support the horizontal aspects of the IoE. The AllSeen Alliance, announced in December 2013, was formed with the goal to advance IoE adoption and innovation in the connected home, healthcare, education, aut...
SYS-CON Events announced today that Red Hat, the world's leading provider of open source solutions, will exhibit at Internet of @ThingsExpo, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Red Hat is the world's leading provider of open source software solutions, using a community-powered approach to reliable and high-performing cloud, Linux, middleware, storage and virtualization technologies. Red Hat also offers award-winning support, training, and consulting services. As the connective hub in a global network of enterprises, partners, a...
The only place to be June 9-11 is Cloud Expo & @ThingsExpo 2015 East at the Javits Center in New York City. Join us there as delegates from all over the world come to listen to and engage with speakers & sponsors from the leading Cloud Computing, IoT & Big Data companies. Cloud Expo & @ThingsExpo are the leading events covering the booming market of Cloud Computing, IoT & Big Data for the enterprise. Speakers from all over the world will be hand-picked for their ability to explore the economic strategies that utility/cloud computing provides. Whether public, private, or in a hybrid form, clo...
Software AG helps organizations transform into Digital Enterprises, so they can differentiate from competitors and better engage customers, partners and employees. Using the Software AG Suite, companies can close the gap between business and IT to create digital systems of differentiation that drive front-line agility. We offer four on-ramps to the Digital Enterprise: alignment through collaborative process analysis; transformation through portfolio management; agility through process automation and integration; and visibility through intelligent business operations and big data.
The Transparent Cloud-computing Consortium (abbreviation: T-Cloud Consortium) will conduct research activities into changes in the computing model as a result of collaboration between "device" and "cloud" and the creation of new value and markets through organic data processing High speed and high quality networks, and dramatic improvements in computer processing capabilities, have greatly changed the nature of applications and made the storing and processing of data on the network commonplace.
Be Among the First 100 to Attend & Receive a Smart Beacon. The Physical Web is an open web project within the Chrome team at Google. Scott Jenson leads a team that is working to leverage the scalability and openness of the web to talk to smart devices. The Physical Web uses bluetooth low energy beacons to broadcast an URL wirelessly using an open protocol. Nearby devices can find all URLs in the room, rank them and let the user pick one from a list. Each device is, in effect, a gateway to a web page. This unlocks entirely new use cases so devices can offer tiny bits of information or simple i...
Things are being built upon cloud foundations to transform organizations. This CEO Power Panel at 15th Cloud Expo, moderated by Roger Strukhoff, Cloud Expo and @ThingsExpo conference chair, will address the big issues involving these technologies and, more important, the results they will achieve. How important are public, private, and hybrid cloud to the enterprise? How does one define Big Data? And how is the IoT tying all this together?
The Internet of Things (IoT) is going to require a new way of thinking and of developing software for speed, security and innovation. This requires IT leaders to balance business as usual while anticipating for the next market and technology trends. Cloud provides the right IT asset portfolio to help today’s IT leaders manage the old and prepare for the new. Today the cloud conversation is evolving from private and public to hybrid. This session will provide use cases and insights to reinforce the value of the network in helping organizations to maximize their company’s cloud experience.
TechCrunch reported that "Berlin-based relayr, maker of the WunderBar, an Internet of Things (IoT) hardware dev kit which resembles a chunky chocolate bar, has closed a $2.3 million seed round, from unnamed U.S. and Switzerland-based investors. The startup had previously raised a €250,000 friend and family round, and had been on track to close a €500,000 seed earlier this year — but received a higher funding offer from a different set of investors, which is the $2.3M round it’s reporting."
The Industrial Internet revolution is now underway, enabled by connected machines and billions of devices that communicate and collaborate. The massive amounts of Big Data requiring real-time analysis is flooding legacy IT systems and giving way to cloud environments that can handle the unpredictable workloads. Yet many barriers remain until we can fully realize the opportunities and benefits from the convergence of machines and devices with Big Data and the cloud, including interoperability, data security and privacy.
All major researchers estimate there will be tens of billions devices - computers, smartphones, tablets, and sensors - connected to the Internet by 2020. This number will continue to grow at a rapid pace for the next several decades. Over the summer Gartner released its much anticipated annual Hype Cycle report and the big news is that Internet of Things has now replaced Big Data as the most hyped technology. Indeed, we're hearing more and more about this fascinating new technological paradigm. Every other IT news item seems to be about IoT and its implications on the future of digital busines...
Cultural, regulatory, environmental, political and economic (CREPE) conditions over the past decade are creating cross-industry solution spaces that require processes and technologies from both the Internet of Things (IoT), and Data Management and Analytics (DMA). These solution spaces are evolving into Sensor Analytics Ecosystems (SAE) that represent significant new opportunities for organizations of all types. Public Utilities throughout the world, providing electricity, natural gas and water, are pursuing SmartGrid initiatives that represent one of the more mature examples of SAE. We have s...
The Internet of Things needs an entirely new security model, or does it? Can we save some old and tested controls for the latest emerging and different technology environments? In his session at Internet of @ThingsExpo, Davi Ottenheimer, EMC Senior Director of Trust, will review hands-on lessons with IoT devices and reveal privacy options and a new risk balance you might not expect.