Welcome!

Java IoT Authors: Dana Gardner, Automic Blog, Pat Romanski, Liz McMillan, Shelly Palmer

Related Topics: Java IoT, Microservices Expo

Java IoT: 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
Is your aging software platform suffering from technical debt while the market changes and demands new solutions at a faster clip? It’s a bold move, but you might consider walking away from your core platform and starting fresh. ReadyTalk did exactly that. In his General Session at 19th Cloud Expo, Michael Chambliss, Head of Engineering at ReadyTalk, will discuss why and how ReadyTalk diverted from healthy revenue and over a decade of audio conferencing product development to start an innovati...
With an estimated 50 billion devices connected to the Internet by 2020, several industries will begin to expand their capabilities for retaining end point data at the edge to better utilize the range of data types and sheer volume of M2M data generated by the Internet of Things. In his session at @ThingsExpo, Don DeLoach, CEO and President of Infobright, discussed the infrastructures businesses will need to implement to handle this explosion of data by providing specific use cases for filterin...
Early adopters of IoT viewed it mainly as a different term for machine-to-machine connectivity or M2M. This is understandable since a prerequisite for any IoT solution is the ability to collect and aggregate device data, which is most often presented in a dashboard. The problem is that viewing data in a dashboard requires a human to interpret the results and take manual action, which doesn’t scale to the needs of IoT.
So, you bought into the current machine learning craze and went on to collect millions/billions of records from this promising new data source. Now, what do you do with them? Too often, the abundance of data quickly turns into an abundance of problems. How do you extract that "magic essence" from your data without falling into the common pitfalls? In her session at @ThingsExpo, Natalia Ponomareva, Software Engineer at Google, provided tips on how to be successful in large scale machine learning...
What does it look like when you have access to cloud infrastructure and platform under the same roof? Let’s talk about the different layers of Technology as a Service: who cares, what runs where, and how does it all fit together. In his session at 18th Cloud Expo, Phil Jackson, Lead Technology Evangelist at SoftLayer, an IBM company, spoke about the picture being painted by IBM Cloud and how the tools being crafted can help fill the gaps in your IT infrastructure.
"C2M is our digital transformation and IoT platform. We've had C2M on the market for almost three years now and it has a comprehensive set of functionalities that it brings to the market," explained Mahesh Ramu, Vice President, IoT Strategy and Operations at Plasma, in this SYS-CON.tv interview at @ThingsExpo, held June 7-9, 2016, at the Javits Center in New York City, NY.
"delaPlex is a software development company. We do team-based outsourcing development," explained Mark Rivers, COO and Co-founder of delaPlex Software, in this SYS-CON.tv interview at 18th Cloud Expo, held June 7-9, 2016, at the Javits Center in New York City, NY.
Whether your IoT service is connecting cars, homes, appliances, wearable, cameras or other devices, one question hangs in the balance – how do you actually make money from this service? The ability to turn your IoT service into profit requires the ability to create a monetization strategy that is flexible, scalable and working for you in real-time. It must be a transparent, smoothly implemented strategy that all stakeholders – from customers to the board – will be able to understand and comprehe...
Traditional IT, great for stable systems of record, is struggling to cope with newer, agile systems of engagement requirements coming straight from the business. In his session at 18th Cloud Expo, William Morrish, General Manager of Product Sales at Interoute, outlined ways of exploiting new architectures to enable both systems and building them to support your existing platforms, with an eye for the future. Technologies such as Docker and the hyper-convergence of computing, networking and sto...
SYS-CON Events announced today that LeaseWeb USA, a cloud Infrastructure-as-a-Service (IaaS) provider, will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. LeaseWeb is one of the world's largest hosting brands. The company helps customers define, develop and deploy IT infrastructure tailored to their exact business needs, by combining various kinds cloud solutions.
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...
It’s 2016: buildings are smart, connected and the IoT is fundamentally altering how control and operating systems work and speak to each other. Platforms across the enterprise are networked via inexpensive sensors to collect massive amounts of data for analytics, information management, and insights that can be used to continuously improve operations. In his session at @ThingsExpo, Brian Chemel, Co-Founder and CTO of Digital Lumens, will explore: The benefits sensor-networked systems bring to ...
SYS-CON Events announced today the Enterprise IoT Bootcamp, being held November 1-2, 2016, in conjunction with 19th Cloud Expo | @ThingsExpo at the Santa Clara Convention Center in Santa Clara, CA. Combined with real-world scenarios and use cases, the Enterprise IoT Bootcamp is not just based on presentations but with hands-on demos and detailed walkthroughs. We will introduce you to a variety of real world use cases prototyped using Arduino, Raspberry Pi, BeagleBone, Spark, and Intel Edison. Y...
Large scale deployments present unique planning challenges, system commissioning hurdles between IT and OT and demand careful system hand-off orchestration. In his session at @ThingsExpo, Jeff Smith, Senior Director and a founding member of Incenergy, will discuss some of the key tactics to ensure delivery success based on his experience of the last two years deploying Industrial IoT systems across four continents.
Much of IT terminology is often misused and misapplied. Modernization and transformation are two such terms. They are often used interchangeably even though they mean different things and have very different connotations. Indeed, it is somewhat safe to assume that in IT any transformative effort is likely to also have a modernizing effect, and thus, we can see these as levels of improvement efforts. However, many businesses are being led to believe if they don’t transform now they risk becoming ...
SYS-CON Events announced today that Venafi, the Immune System for the Internet™ and the leading provider of Next Generation Trust Protection, will exhibit at @DevOpsSummit at 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Venafi is the Immune System for the Internet™ that protects the foundation of all cybersecurity – cryptographic keys and digital certificates – so they can’t be misused by bad guys in attacks...
Identity is in everything and customers are looking to their providers to ensure the security of their identities, transactions and data. With the increased reliance on cloud-based services, service providers must build security and trust into their offerings, adding value to customers and improving the user experience. Making identity, security and privacy easy for customers provides a unique advantage over the competition.
Whether your IoT service is connecting cars, homes, appliances, wearable, cameras or other devices, one question hangs in the balance – how do you actually make money from this service? The ability to turn your IoT service into profit requires the ability to create a monetization strategy that is flexible, scalable and working for you in real-time. It must be a transparent, smoothly implemented strategy that all stakeholders – from customers to the board – will be able to understand and comprehe...
"Tintri was started in 2008 with the express purpose of building a storage appliance that is ideal for virtualized environments. We support a lot of different hypervisor platforms from VMware to OpenStack to Hyper-V," explained Dan Florea, Director of Product Management at Tintri, in this SYS-CON.tv interview at 18th Cloud Expo, held June 7-9, 2016, at the Javits Center in New York City, NY.
"There's a growing demand from users for things to be faster. When you think about all the transactions or interactions users will have with your product and everything that is between those transactions and interactions - what drives us at Catchpoint Systems is the idea to measure that and to analyze it," explained Leo Vasiliou, Director of Web Performance Engineering at Catchpoint Systems, in this SYS-CON.tv interview at 18th Cloud Expo, held June 7-9, 2016, at the Javits Center in New York Ci...