|By Dan North||
|March 5, 2004 12:00 AM EST||
The vast majority of Java enterprise applications are architected along the lines of Sun's original PetStore showcase application. Rather than seeing this as a market stall displaying all the J2EE goods on offer, developers took it as a blueprint for enterprise applications. It certainly created a lot of work for Java application developers (as well as systems administrators and systems integrators), but whether most of the applications needed most of the possible layers - including bean-managed persistence and the ubiquitous DAO - is open for question at the very least. This article briefly describes some of the testability shortcomings of the traditional J2EE model and presents some alternatives.
The J2EE Model
With J2EE we are tied to a single logical server in a client/server architecture, and any component such as a servlet or EJB has to be deployed to the server (potentially a time-consuming process) before we know whether it works. This makes it difficult to use test-driven techniques to develop these components. To make a small change to such a component requires a code change, a recompile, and a redeploy. On many commercial application servers this sequence of events takes too long to be repeated as frequently as TDD requires. The developer is encouraged to deploy bigger changes less often, and therefore has a higher risk of introducing errors.
A few patterns alleviate some of this, most notably the Front Controller/Dispatcher pattern. This has a single component (a servlet in the Web container or a stateless session bean in the EJB tier) that dispatches requests to a POJO (Plain Old Java Object). A POJO is much better suited for unit testing - we can simply instantiate it in a known state and then exercise its behavior. From a TDD perspective, this is what makes a framework like WebWork more "agile" than Struts; for instance, the actual components are testable outside of a container.
J2EE encourages us to model a system in terms of components interacting with one another. Instead we can model in terms of services that an application provides or "things that it does." These services can exist on different machines or in different virtual machines on the same host. As long as we have a means of locating a service, we can use it. In terms of testability, this makes life a lot easier for us. A service is simply a class that implements an interface, so we can test its behavior in isolation or in conjunction with other services just by instantiating a service object and calling methods on it.
Service-oriented mechanisms such as SOAP, XML-RPC, or JINI are cleanly separated from the actual services they advertise. Compare this to a session bean, which is tightly coupled to its container: it requires a number of container-specific classes just to function (such as a javax.ejb. SessionContext), and has a whole complex life cycle associated with it. Both of these make testing a session bean a lot more complex - and add greatly to the time it takes to make a change and test it.
So far we have focused on synchronous behavior. The concept of modeling a system in terms of messages or events being produced and consumed asynchronously from queues is very powerful and yet still largely overlooked. Event-driven systems are renowned for their resilience, but they also lend themselves very nicely to a test-driven approach. As with services, an event consumer or listener is typically a Java class that implements an interface. As long as the consumer class is decoupled from the delivery mechanism, we can easily test its behavior. We can model synchronous behavior asynchronously to gain both scalability and testability. A Staged, Event-Driven Architecture (SEDA) simulates synchronous processing by means of a series of stages, each represented by a queue. Thus each stage can be unit-tested and developed separately.
When you're writing an enterprise application in Java, you shouldn't feel constrained to the classic J2EE model. Investigate some of the alternatives; ask lots of questions; and evaluate the costs, benefits, and risks of using a different approach. But most important, as a developer try to find an architecture that enables you to write testable code. Remember, PetStore is a showcase of technologies, not a blueprint.
|Tom 03/10/04 12:44:18 AM EST|
I agree on the statements made here. Personally I use the approach of moving all logic into POJO''s, which have no knowledge of how their functionality is made public. The servlet or EJB or webservice doing that, is just a hand-through taking care of the appropriate protocol.
|Tom 03/10/04 12:43:24 AM EST|
I agree on the statements made here. Personally I use the approach of moving all logic into POJO''s, which have no knowledge of how their functionality is made public. The servlet or EJB or webserver doing that, is just a hand-through taking care data of the appropriate protocol.
SYS-CON Events announced today that Peak 10, Inc., a national IT infrastructure and cloud services provider, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. Peak 10 provides reliable, tailored data center and network services, cloud and managed services. Its solutions are designed to scale and adapt to customers’ changing business needs, enabling them to lower costs, improve performance and focus inter...
May. 1, 2016 12:00 AM EDT Reads: 1,053
You think you know what’s in your data. But do you? Most organizations are now aware of the business intelligence represented by their data. Data science stands to take this to a level you never thought of – literally. The techniques of data science, when used with the capabilities of Big Data technologies, can make connections you had not yet imagined, helping you discover new insights and ask new questions of your data. In his session at @ThingsExpo, Sarbjit Sarkaria, data science team lead ...
Apr. 30, 2016 10:45 PM EDT Reads: 677
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, will provide tips on how to be successful in large scale machine lear...
Apr. 30, 2016 10:00 PM EDT Reads: 1,091
In his session at @ThingsExpo, Chris Klein, CEO and Co-founder of Rachio, will discuss next generation communities that are using IoT to create more sustainable, intelligent communities. One example is Sterling Ranch, a 10,000 home development that – with the help of Siemens – will integrate IoT technology into the community to provide residents with energy and water savings as well as intelligent security. Everything from stop lights to sprinkler systems to building infrastructures will run ef...
Apr. 30, 2016 05:30 PM EDT Reads: 715
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...
Apr. 30, 2016 04:45 PM EDT Reads: 1,055
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, will discuss how research has demonstrated the value of Machine Learning in delivering next generation analytics to im...
Apr. 30, 2016 04:15 PM EDT Reads: 1,667
There is an ever-growing explosion of new devices that are connected to the Internet using “cloud” solutions. This rapid growth is creating a massive new demand for efficient access to data. And it’s not just about connecting to that data anymore. This new demand is bringing new issues and challenges and it is important for companies to scale for the coming growth. And with that scaling comes the need for greater security, gathering and data analysis, storage, connectivity and, of course, the...
Apr. 30, 2016 03:15 PM EDT Reads: 763
This is not a small hotel event. It is also not a big vendor party where politicians and entertainers are more important than real content. This is Cloud Expo, the world's longest-running conference and exhibition focused on Cloud Computing and all that it entails. If you want serious presentations and valuable insight about Cloud Computing for three straight days, then register now for Cloud Expo.
Apr. 30, 2016 02:30 PM EDT Reads: 1,715
IoT device adoption is growing at staggering rates, and with it comes opportunity for developers to meet consumer demand for an ever more connected world. Wireless communication is the key part of the encompassing components of any IoT device. Wireless connectivity enhances the device utility at the expense of ease of use and deployment challenges. Since connectivity is fundamental for IoT device development, engineers must understand how to overcome the hurdles inherent in incorporating multipl...
Apr. 30, 2016 02:15 PM EDT Reads: 1,454
SYS-CON Events announced today that Stratoscale, the software company developing the next generation data center operating system, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. Stratoscale is revolutionizing the data center with a zero-to-cloud-in-minutes solution. With Stratoscale’s hardware-agnostic, Software Defined Data Center (SDDC) solution to store everything, run anything and scale everywhere...
Apr. 30, 2016 01:15 PM EDT Reads: 1,532
The increasing popularity of the Internet of Things necessitates that our physical and cognitive relationship with wearable technology will change rapidly in the near future. This advent means logging has become a thing of the past. Before, it was on us to track our own data, but now that data is automatically available. What does this mean for mHealth and the "connected" body? In her session at @ThingsExpo, Lisa Calkins, CEO and co-founder of Amadeus Consulting, will discuss the impact of wea...
Apr. 30, 2016 01:15 PM EDT Reads: 666
Angular 2 is a complete re-write of the popular framework AngularJS. Programming in Angular 2 is greatly simplified – now it's a component-based well-performing framework. This immersive one-day workshop at 18th Cloud Expo, led by Yakov Fain, a Java Champion and a co-founder of the IT consultancy Farata Systems and the product company SuranceBay, will provide you with everything you wanted to know about Angular 2.
Apr. 30, 2016 12:45 PM EDT Reads: 1,703
SYS-CON Events announced today that Men & Mice, the leading global provider of DNS, DHCP and IP address management overlay solutions, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. The Men & Mice Suite overlay solution is already known for its powerful application in heterogeneous operating environments, enabling enterprises to scale without fuss. Building on a solid range of diverse platform support,...
Apr. 30, 2016 12:00 PM EDT Reads: 2,295
You deployed your app with the Bluemix PaaS and it's gaining some serious traction, so it's time to make some tweaks. Did you design your application in a way that it can scale in the cloud? Were you even thinking about the cloud when you built the app? If not, chances are your app is going to break. Check out this webcast to learn various techniques for designing applications that will scale successfully in Bluemix, for the confidence you need to take your apps to the next level and beyond.
Apr. 30, 2016 11:30 AM EDT Reads: 1,469
We’ve worked with dozens of early adopters across numerous industries and will debunk common misperceptions, which starts with understanding that many of the connected products we’ll use over the next 5 years are already products, they’re just not yet connected. With an IoT product, time-in-market provides much more essential feedback than ever before. Innovation comes from what you do with the data that the connected product provides in order to enhance the customer experience and optimize busi...
Apr. 30, 2016 11:15 AM EDT Reads: 889
SYS-CON Events announced today that Ericsson has been named “Gold Sponsor” of SYS-CON's @ThingsExpo, which will take place on June 7-9, 2016, at the Javits Center in New York, New York. Ericsson is a world leader in the rapidly changing environment of communications technology – providing equipment, software and services to enable transformation through mobility. Some 40 percent of global mobile traffic runs through networks we have supplied. More than 1 billion subscribers around the world re...
Apr. 30, 2016 11:00 AM EDT Reads: 878
Increasing IoT connectivity is forcing enterprises to find elegant solutions to organize and visualize all incoming data from these connected devices with re-configurable dashboard widgets to effectively allow rapid decision-making for everything from immediate actions in tactical situations to strategic analysis and reporting. In his session at 18th Cloud Expo, Shikhir Singh, Senior Developer Relations Manager at Sencha, will discuss how to create HTML5 dashboards that interact with IoT devic...
Apr. 30, 2016 11:00 AM EDT Reads: 925
Artificial Intelligence has the potential to massively disrupt IoT. In his session at 18th Cloud Expo, AJ Abdallat, CEO of Beyond AI, will discuss what the five main drivers are in Artificial Intelligence that could shape the future of the Internet of Things. AJ Abdallat is CEO of Beyond AI. He has over 20 years of management experience in the fields of artificial intelligence, sensors, instruments, devices and software for telecommunications, life sciences, environmental monitoring, process...
Apr. 30, 2016 11:00 AM EDT Reads: 897
Digital payments using wearable devices such as smart watches, fitness trackers, and payment wristbands are an increasing area of focus for industry participants, and consumer acceptance from early trials and deployments has encouraged some of the biggest names in technology and banking to continue their push to drive growth in this nascent market. Wearable payment systems may utilize near field communication (NFC), radio frequency identification (RFID), or quick response (QR) codes and barcodes...
Apr. 30, 2016 10:00 AM EDT Reads: 718
SYS-CON Events announced today that Fusion, a leading provider of cloud services, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. Fusion, a leading provider of integrated cloud solutions to small, medium and large businesses, is the industry's single source for the cloud. Fusion's advanced, proprietary cloud service platform enables the integration of leading edge solutions in the cloud, including cloud...
Apr. 30, 2016 09:45 AM EDT Reads: 2,560