Welcome!

Java IoT Authors: Elizabeth White, Liz McMillan, Pat Romanski, Sematext Blog, Xenia von Wedel

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
"Once customers get a year into their IoT deployments, they start to realize that they may have been shortsighted in the ways they built out their deployment and the key thing I see a lot of people looking at is - how can I take equipment data, pull it back in an IoT solution and show it in a dashboard," stated Dave McCarthy, Director of Products at Bsquare Corporation, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
The cloud promises new levels of agility and cost-savings for Big Data, data warehousing and analytics. But it’s challenging to understand all the options – from IaaS and PaaS to newer services like HaaS (Hadoop as a Service) and BDaaS (Big Data as a Service). In her session at @BigDataExpo at @ThingsExpo, Hannah Smalltree, a director at Cazena, provided an educational overview of emerging “as-a-service” options for Big Data in the cloud. This is critical background for IT and data professionals...
Fact is, enterprises have significant legacy voice infrastructure that’s costly to replace with pure IP solutions. How can we bring this analog infrastructure into our shiny new cloud applications? There are proven methods to bind both legacy voice applications and traditional PSTN audio into cloud-based applications and services at a carrier scale. Some of the most successful implementations leverage WebRTC, WebSockets, SIP and other open source technologies. In his session at @ThingsExpo, Da...
As data explodes in quantity, importance and from new sources, the need for managing and protecting data residing across physical, virtual, and cloud environments grow with it. Managing data includes protecting it, indexing and classifying it for true, long-term management, compliance and E-Discovery. Commvault can ensure this with a single pane of glass solution – whether in a private cloud, a Service Provider delivered public cloud or a hybrid cloud environment – across the heterogeneous enter...
"IoT is going to be a huge industry with a lot of value for end users, for industries, for consumers, for manufacturers. How can we use cloud to effectively manage IoT applications," stated Ian Khan, Innovation & Marketing Manager at Solgeniakhela, in this SYS-CON.tv interview at @ThingsExpo, held November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA.
Today we can collect lots and lots of performance data. We build beautiful dashboards and even have fancy query languages to access and transform the data. Still performance data is a secret language only a couple of people understand. The more business becomes digital the more stakeholders are interested in this data including how it relates to business. Some of these people have never used a monitoring tool before. They have a question on their mind like “How is my application doing” but no id...
@GonzalezCarmen has been ranked the Number One Influencer and @ThingsExpo has been named the Number One Brand in the “M2M 2016: Top 100 Influencers and Brands” by Onalytica. Onalytica analyzed tweets over the last 6 months mentioning the keywords M2M OR “Machine to Machine.” They then identified the top 100 most influential brands and individuals leading the discussion on Twitter.
Information technology is an industry that has always experienced change, and the dramatic change sweeping across the industry today could not be truthfully described as the first time we've seen such widespread change impacting customer investments. However, the rate of the change, and the potential outcomes from today's digital transformation has the distinct potential to separate the industry into two camps: Organizations that see the change coming, embrace it, and successful leverage it; and...
The Internet of Things (IoT) promises to simplify and streamline our lives by automating routine tasks that distract us from our goals. This promise is based on the ubiquitous deployment of smart, connected devices that link everything from industrial control systems to automobiles to refrigerators. Unfortunately, comparatively few of the devices currently deployed have been developed with an eye toward security, and as the DDoS attacks of late October 2016 have demonstrated, this oversight can ...
Extracting business value from Internet of Things (IoT) data doesn’t happen overnight. There are several requirements that must be satisfied, including IoT device enablement, data analysis, real-time detection of complex events and automated orchestration of actions. Unfortunately, too many companies fall short in achieving their business goals by implementing incomplete solutions or not focusing on tangible use cases. In his general session at @ThingsExpo, Dave McCarthy, Director of Products...
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 impr...
More and more brands have jumped on the IoT bandwagon. We have an excess of wearables – activity trackers, smartwatches, smart glasses and sneakers, and more that track seemingly endless datapoints. However, most consumers have no idea what “IoT” means. Creating more wearables that track data shouldn't be the aim of brands; delivering meaningful, tangible relevance to their users should be. We're in a period in which the IoT pendulum is still swinging. Initially, it swung toward "smart for smar...
20th Cloud Expo, taking place June 6-8, 2017, at the Javits Center in New York City, NY, 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.
Businesses and business units of all sizes can benefit from cloud computing, but many don't want the cost, performance and security concerns of public cloud nor the complexity of building their own private clouds. Today, some cloud vendors are using artificial intelligence (AI) to simplify cloud deployment and management. In his session at 20th Cloud Expo, Ajay Gulati, Co-founder and CEO of ZeroStack, will discuss how AI can simplify cloud operations. He will cover the following topics: why clou...
Internet of @ThingsExpo, taking place June 6-8, 2017 at the Javits Center in New York City, New York, is co-located with the 20th International Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. @ThingsExpo New York Call for Papers is now open.
"ReadyTalk is an audio and web video conferencing provider. We've really come to embrace WebRTC as the platform for our future of technology," explained Dan Cunningham, CTO of ReadyTalk, in this SYS-CON.tv interview at WebRTC Summit at 19th Cloud Expo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
Successful digital transformation requires new organizational competencies and capabilities. Research tells us that the biggest impediment to successful transformation is human; consequently, the biggest enabler is a properly skilled and empowered workforce. In the digital age, new individual and collective competencies are required. In his session at 19th Cloud Expo, Bob Newhouse, CEO and founder of Agilitiv, drew together recent research and lessons learned from emerging and established compa...
Data is the fuel that drives the machine learning algorithmic engines and ultimately provides the business value. In his session at Cloud Expo, Ed Featherston, a director and senior enterprise architect at Collaborative Consulting, discussed the key considerations around quality, volume, timeliness, and pedigree that must be dealt with in order to properly fuel that engine.
Everyone knows that truly innovative companies learn as they go along, pushing boundaries in response to market changes and demands. What's more of a mystery is how to balance innovation on a fresh platform built from scratch with the legacy tech stack, product suite and customers that continue to serve as the business' foundation. In his General Session at 19th Cloud Expo, Michael Chambliss, Head of Engineering at ReadyTalk, discussed why and how ReadyTalk diverted from healthy revenue and mor...
We are always online. We access our data, our finances, work, and various services on the Internet. But we live in a congested world of information in which the roads were built two decades ago. The quest for better, faster Internet routing has been around for a decade, but nobody solved this problem. We’ve seen band-aid approaches like CDNs that attack a niche's slice of static content part of the Internet, but that’s it. It does not address the dynamic services-based Internet of today. It does...