Welcome!

Java IoT Authors: Stackify Blog, Pat Romanski, Liz McMillan, Elizabeth White, Yeshim Deniz

Related Topics: Java IoT

Java IoT: Article

Inversion of Control Rocks

Inversion of Control Rocks

Inversion of Control (IoC) is about software components doing what they are told, when they are told. Your OO application could well become unmaintainable without it.

IoC is a pattern that helps teams avoid the dependency hell that results when an application grows into a large pseudo-platform without taking care to adequately decouple logic; that thing that ultimately only a couple of its omnipotent architects or old-lag premium-rate contractors really understand; that system that Heath Robinson and Rube Goldberg might have made together (look them up).

The problem with small working applications that become large is that static-method entanglement does not scale. One part of a system that's otherwise fairly self-contained statically accesses another part of the system and cannot be instantiated without invoking methods in the latter. Thus it can't easily be isolated for unit testing. What's more, it can't be developed as an independent component. Components that are developed separately can have their own development teams and may well be part of a larger design. These components will have their own source control directory and can be developed against mock implementations of their dependent components. All this will help overall development become faster, in terms of both the team's efficiency and the build time.

As an example, let's take a Personal Information Manager (PIM) application that has UI and persistence elements. The naïve implementation might have inline JDBC statements among graphical code. A componentized application would have that persistence logic separated into a persistence component with user interface logic enshrined in a view-controller component. Clearly, if the two teams developing their respective components agree on a slowly evolving interface/implementation-separated API for persistence, they can develop at their own pace and ship versions of their components whenever it's appropriate.

A third piece, which is not a component, would be the bootstrap for the application. That bootstrap may well be entirely contained in a static main method of a simple class and would merely instantiate the two components, passing one into the other's constructor before invoking setVisible(true) or similar. With the introduction of this bootstrap we can see the control aspect of the IoC pattern.

In a noncomponentized version of our example, the view-controller may well have its own main method, might instantiate a fixed version of the PIM store, or access it via an unnecessary singleton factory (public static methods are generally bad), i.e., the control is very much inside the component in question.

The word "inversion" from the pattern name is about getting control back. The containing application (often a true container or a proper framework rather than a main method) controls when a component is instantiated and which implementations of its dependent components it is passed.

IoC also dictates the configuration of components. A JDBC version of the PIM store above would clearly require some JDBC settings. Classically, developers may write a mechanism to retrieve them from a fixed properties file. IoC would insist that the configuration is passed into the component. In our hypothetical example, it would take it via the constructor and be interface/implementation separated. Thus the configuration is a component. It would be tightly coupled to the component that requires it, but subject to multiple implementations, one of which may be the "from properties file".

Inversion of Control has moved to the center stage in the last six months after a five-year gestation period. There are three types of Inversion of Control. Type 1 uses configuration data (Avalon, JContainer); Type 2 uses bean introspection (Spring Framework, WebWork2, HiveMind); Type 3 uses constructor signatures (PicoContainer).

For a componentized system that uses singletons or similar for component resolution, the dependency is obscure. In IoC it is declarative. The application would have loosely coupled components and be more scalable, more maintainable, and more testable. It's a very small investment for a very large return. Inversion of Control rocks.

More Stories By Paul Hammant

Paul Hammant is a still-coding architect for ThoughtWorks in London and has been programming professionally since 1989. He was a former committer on Apache’s Avalon project, but left and cofounded the open-source PicoContainer project and its sister NanoContainer as well as remaining involved the post-Avalon JContainer project.

Comments (4) View Comments

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


Most Recent Comments
Eric Herman 12/09/03 08:40:08 PM EST

I''m glad that this subject is getting some more attention and we''re starting to think a bit more about it. My experiences have taught me to think of the use of static variables and static methods as a hint that I need to be thinking more about design. I''m not sure that the name "Inversion of Control" communicates the issue, but I don''t have a better name. I often use the phase "statics hurt" when talking about design. If possible, see if statics can be avoided entirely in your application. If not, how close can we get? Maybe we can hold a reference to a instance (which we can then mock out for testing) rather than use a static? Maybe a ThreadLocal can help? And who knows, maybe we''ll start to see some possibilities for polymorphism or plugabillity that were previously unavailable to us?

Rob 12/06/03 08:03:22 PM EST

IoC rocks indeed! (and also nice to know there''s actually a name for what i''ve been doing :-)

Juergen Hoeller 12/05/03 08:13:18 AM EST

FYI: Since 1.0 M3, the Spring Framework''s bean factory supports both Type 2 IoC (bean property resolution) and Type 3 IoC (constructor resolution).

Juergen Hoeller 12/05/03 08:13:12 AM EST

FYI: Since 1.0 M3, the Spring Framework''s bean factory supports both Type 2 IoC (bean property resolution) and Type 3 IoC (constructor resolution).

@ThingsExpo Stories
SYS-CON Events announced today that IBM has been named “Diamond Sponsor” of SYS-CON's 21st Cloud Expo, which will take place on October 31 through November 2nd 2017 at the Santa Clara Convention Center in Santa Clara, California.
When growing capacity and power in the data center, the architectural trade-offs between server scale-up vs. scale-out continue to be debated. Both approaches are valid: scale-out adds multiple, smaller servers running in a distributed computing model, while scale-up adds fewer, more powerful servers that are capable of running larger workloads. It’s worth noting that there are additional, unique advantages that scale-up architectures offer. One big advantage is large memory and compute capacity...
In his session at @ThingsExpo, Eric Lachapelle, CEO of the Professional Evaluation and Certification Board (PECB), provided an overview of various initiatives to certify the security of connected devices and future trends in ensuring public trust of IoT. Eric Lachapelle is the Chief Executive Officer of the Professional Evaluation and Certification Board (PECB), an international certification body. His role is to help companies and individuals to achieve professional, accredited and worldwide re...
With major technology companies and startups seriously embracing Cloud strategies, now is the perfect time to attend 21st Cloud Expo October 31 - November 2, 2017, at the Santa Clara Convention Center, CA, and June 12-14, 2018, at the Javits Center in New York City, NY, and learn what is going on, contribute to the discussions, and ensure that your enterprise is on the right path to Digital Transformation.
No hype cycles or predictions of zillions of things here. IoT is big. You get it. You know your business and have great ideas for a business transformation strategy. What comes next? Time to make it happen. In his session at @ThingsExpo, Jay Mason, Associate Partner at M&S Consulting, presented a step-by-step plan to develop your technology implementation strategy. He discussed the evaluation of communication standards and IoT messaging protocols, data analytics considerations, edge-to-cloud tec...
Amazon started as an online bookseller 20 years ago. Since then, it has evolved into a technology juggernaut that has disrupted multiple markets and industries and touches many aspects of our lives. It is a relentless technology and business model innovator driving disruption throughout numerous ecosystems. Amazon’s AWS revenues alone are approaching $16B a year making it one of the largest IT companies in the world. With dominant offerings in Cloud, IoT, eCommerce, Big Data, AI, Digital Assista...
SYS-CON Events announced today that CA Technologies has been named "Platinum Sponsor" of SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. CA Technologies helps customers succeed in a future where every business - from apparel to energy - is being rewritten by software. From planning to development to management to security, CA creates software that fuels transformation for companies in the applic...
Artificial intelligence, machine learning, neural networks. We’re in the midst of a wave of excitement around AI such as hasn’t been seen for a few decades. But those previous periods of inflated expectations led to troughs of disappointment. Will this time be different? Most likely. Applications of AI such as predictive analytics are already decreasing costs and improving reliability of industrial machinery. Furthermore, the funding and research going into AI now comes from a wide range of com...
Multiple data types are pouring into IoT deployments. Data is coming in small packages as well as enormous files and data streams of many sizes. Widespread use of mobile devices adds to the total. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, panelists looked at the tools and environments that are being put to use in IoT deployments, as well as the team skills a modern enterprise IT shop needs to keep things running, get a handle on all this data, and deliver...
Internet of @ThingsExpo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 21st 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 devic...
SYS-CON Events announced today that Cloud Academy named "Bronze Sponsor" of 21st International Cloud Expo which will take place October 31 - November 2, 2017 at the Santa Clara Convention Center in Santa Clara, CA. Cloud Academy is the industry’s most innovative, vendor-neutral cloud technology training platform. Cloud Academy provides continuous learning solutions for individuals and enterprise teams for Amazon Web Services, Microsoft Azure, Google Cloud Platform, and the most popular cloud com...
SYS-CON Events announced today that Enzu will exhibit at SYS-CON's 21st Int\ernational Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Enzu’s mission is to be the leading provider of enterprise cloud solutions worldwide. Enzu enables online businesses to use its IT infrastructure to their competitive advantage. By offering a suite of proven hosting and management services, Enzu wants companies to focus on the core of their ...
We build IoT infrastructure products - when you have to integrate different devices, different systems and cloud you have to build an application to do that but we eliminate the need to build an application. Our products can integrate any device, any system, any cloud regardless of protocol," explained Peter Jung, Chief Product Officer at Pulzze Systems, in this SYS-CON.tv interview at @ThingsExpo, held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA
SYS-CON Events announced today that GrapeUp, the leading provider of rapid product development at the speed of business, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Grape Up is a software company, specialized in cloud native application development and professional services related to Cloud Foundry PaaS. With five expert teams that operate in various sectors of the market acr...
SYS-CON Events announced today that Ayehu will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on October 31 - November 2, 2017 at the Santa Clara Convention Center in Santa Clara California. Ayehu provides IT Process Automation & Orchestration solutions for IT and Security professionals to identify and resolve critical incidents and enable rapid containment, eradication, and recovery from cyber security breaches. Ayehu provides customers greater control over IT infras...
SYS-CON Events announced today that MobiDev, a client-oriented software development company, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place October 31-November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. MobiDev is a software company that develops and delivers turn-key mobile apps, websites, web services, and complex software systems for startups and enterprises. Since 2009 it has grown from a small group of passionate engineers and business...
In his session at Cloud Expo, Alan Winters, an entertainment executive/TV producer turned serial entrepreneur, presented a success story of an entrepreneur who has both suffered through and benefited from offshore development across multiple businesses: The smart choice, or how to select the right offshore development partner Warning signs, or how to minimize chances of making the wrong choice Collaboration, or how to establish the most effective work processes Budget control, or how to ma...
"When we talk about cloud without compromise what we're talking about is that when people think about 'I need the flexibility of the cloud' - it's the ability to create applications and run them in a cloud environment that's far more flexible,” explained Matthew Finnie, CTO of Interoute, in this SYS-CON.tv interview at 20th Cloud Expo, held June 6-8, 2017, at the Javits Center in New York City, NY.
IoT solutions exploit operational data generated by Internet-connected smart “things” for the purpose of gaining operational insight and producing “better outcomes” (for example, create new business models, eliminate unscheduled maintenance, etc.). The explosive proliferation of IoT solutions will result in an exponential growth in the volume of IoT data, precipitating significant Information Governance issues: who owns the IoT data, what are the rights/duties of IoT solutions adopters towards t...
With the introduction of IoT and Smart Living in every aspect of our lives, one question has become relevant: What are the security implications? To answer this, first we have to look and explore the security models of the technologies that IoT is founded upon. In his session at @ThingsExpo, Nevi Kaja, a Research Engineer at Ford Motor Company, discussed some of the security challenges of the IoT infrastructure and related how these aspects impact Smart Living. The material was delivered interac...