Welcome!

Java IoT Authors: Stackify Blog, Yeshim Deniz, Pat Romanski, Matt Lonstine, Glenda Sims

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
DX World EXPO, LLC, a Lighthouse Point, Florida-based startup trade show producer and the creator of "DXWorldEXPO® - Digital Transformation Conference & Expo" has announced its executive management team. The team is headed by Levent Selamoglu, who has been named CEO. "Now is the time for a truly global DX event, to bring together the leading minds from the technology world in a conversation about Digital Transformation," he said in making the announcement.
"Space Monkey by Vivent Smart Home is a product that is a distributed cloud-based edge storage network. Vivent Smart Home, our parent company, is a smart home provider that places a lot of hard drives across homes in North America," explained JT Olds, Director of Engineering, and Brandon Crowfeather, Product Manager, at Vivint Smart Home, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
SYS-CON Events announced today that Conference Guru has been named “Media Sponsor” of the 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. A valuable conference experience generates new contacts, sales leads, potential strategic partners and potential investors; helps gather competitive intelligence and even provides inspiration for new products and services. Conference Guru works with conference organizers to pass great deals to gre...
The Internet of Things will challenge the status quo of how IT and development organizations operate. Or will it? Certainly the fog layer of IoT requires special insights about data ontology, security and transactional integrity. But the developmental challenges are the same: People, Process and Platform. In his session at @ThingsExpo, Craig Sproule, CEO of Metavine, demonstrated how to move beyond today's coding paradigm and shared the must-have mindsets for removing complexity from the develop...
In his Opening Keynote at 21st Cloud Expo, John Considine, General Manager of IBM Cloud Infrastructure, led attendees through the exciting evolution of the cloud. He looked at this major disruption from the perspective of technology, business models, and what this means for enterprises of all sizes. John Considine is General Manager of Cloud Infrastructure Services at IBM. In that role he is responsible for leading IBM’s public cloud infrastructure including strategy, development, and offering m...
"Evatronix provides design services to companies that need to integrate the IoT technology in their products but they don't necessarily have the expertise, knowledge and design team to do so," explained Adam Morawiec, VP of Business Development at Evatronix, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. In his session at @BigDataExpo, Jack Norris, Senior Vice President, Data and Applications at MapR Technologies, reviewed best practices to ...
Widespread fragmentation is stalling the growth of the IIoT and making it difficult for partners to work together. The number of software platforms, apps, hardware and connectivity standards is creating paralysis among businesses that are afraid of being locked into a solution. EdgeX Foundry is unifying the community around a common IoT edge framework and an ecosystem of interoperable components.
Large industrial manufacturing organizations are adopting the agile principles of cloud software companies. The industrial manufacturing development process has not scaled over time. Now that design CAD teams are geographically distributed, centralizing their work is key. With large multi-gigabyte projects, outdated tools have stifled industrial team agility, time-to-market milestones, and impacted P&L stakeholders.
"Akvelon is a software development company and we also provide consultancy services to folks who are looking to scale or accelerate their engineering roadmaps," explained Jeremiah Mothersell, Marketing Manager at Akvelon, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
"IBM is really all in on blockchain. We take a look at sort of the history of blockchain ledger technologies. It started out with bitcoin, Ethereum, and IBM evaluated these particular blockchain technologies and found they were anonymous and permissionless and that many companies were looking for permissioned blockchain," stated René Bostic, Technical VP of the IBM Cloud Unit in North America, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventi...
In his session at 21st Cloud Expo, Carl J. Levine, Senior Technical Evangelist for NS1, will objectively discuss how DNS is used to solve Digital Transformation challenges in large SaaS applications, CDNs, AdTech platforms, and other demanding use cases. Carl J. Levine is the Senior Technical Evangelist for NS1. A veteran of the Internet Infrastructure space, he has over a decade of experience with startups, networking protocols and Internet infrastructure, combined with the unique ability to it...
22nd International Cloud Expo, taking place June 5-7, 2018, at the Javits Center in New York City, NY, and co-located with the 1st DXWorld Expo 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 ...
"Cloud Academy is an enterprise training platform for the cloud, specifically public clouds. We offer guided learning experiences on AWS, Azure, Google Cloud and all the surrounding methodologies and technologies that you need to know and your teams need to know in order to leverage the full benefits of the cloud," explained Alex Brower, VP of Marketing at Cloud Academy, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clar...
Gemini is Yahoo’s native and search advertising platform. To ensure the quality of a complex distributed system that spans multiple products and components and across various desktop websites and mobile app and web experiences – both Yahoo owned and operated and third-party syndication (supply), with complex interaction with more than a billion users and numerous advertisers globally (demand) – it becomes imperative to automate a set of end-to-end tests 24x7 to detect bugs and regression. In th...
"MobiDev is a software development company and we do complex, custom software development for everybody from entrepreneurs to large enterprises," explained Alan Winters, U.S. Head of Business Development at MobiDev, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
Coca-Cola’s Google powered digital signage system lays the groundwork for a more valuable connection between Coke and its customers. Digital signs pair software with high-resolution displays so that a message can be changed instantly based on what the operator wants to communicate or sell. In their Day 3 Keynote at 21st Cloud Expo, Greg Chambers, Global Group Director, Digital Innovation, Coca-Cola, and Vidya Nagarajan, a Senior Product Manager at Google, discussed how from store operations and ...
"There's plenty of bandwidth out there but it's never in the right place. So what Cedexis does is uses data to work out the best pathways to get data from the origin to the person who wants to get it," explained Simon Jones, Evangelist and Head of Marketing at Cedexis, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
SYS-CON Events announced today that CrowdReviews.com has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5–7, 2018, at the Javits Center in New York City, NY. CrowdReviews.com is a transparent online platform for determining which products and services are the best based on the opinion of the crowd. The crowd consists of Internet users that have experienced products and services first-hand and have an interest in letting other potential buye...
SYS-CON Events announced today that Telecom Reseller has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. Telecom Reseller reports on Unified Communications, UCaaS, BPaaS for enterprise and SMBs. They report extensively on both customer premises based solutions such as IP-PBX as well as cloud based and hosted platforms.