Welcome!

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

Related Topics: Java IoT

Java IoT: Article

SOA Solutions with J2EE

Using different technical and functional requirements

Throughout this article I'll describe how an effective service-oriented architecture (SOA) can be achieved using J2EE technologies. In particular, I'll focus on which J2EE component types and communication channels to choose according to specific, real-world situations.

Description of the Example System
To illustrate an SOA system made of J2EE technologies, nothing is better than a good old example. Figure 1 depicts the main situations that can arise in a realistic SOA system. A component stereotype indicates the type of client or service; a dependency stereotype indicates the communication type, either as a technology (such as Web services) or as a protocol (such as CORBA IIOP); and a no dependency stereotype indicates RMI communication.

The system allows client systems to process an order (service OrderWorkflow), manage customers (service Customer), and produce reports (service Reporting). The OrderWorkflow service checks product availability and retrieves product details (service Product), creates a new customer if needed (service Customer), and orders the selected products (service Order). The Order service persists the order (service OrderData), manages the payment (service Payment), and triggers some process in a legacy system (service BackOfficeOrder).

Service Layers
Services differ according to multiple criteria. Whether the service is business oriented, public or private, or stateful or stateless dictates what layer the service is in and ultimately how it is implemented and what interfaces it exposes.

Top-layer services such as OrderWorkflow are coarse-grained business services, often stateful, that depend on one or more finer-grained stateless business services. Bottom-layer services are fine grained and data oriented, not business oriented.

Services are also separated into public and private services. Public services are services that are available outside of the system, and possibly outside of the organization. They are typically services that have a business meaning. Private services have no business meaning; they exist to support business services and there's no point in making them available to other systems. In Figure 1, public services are colored in blue and private services are not colored.

Although the number of layers of an SOA system is arbitrary, we can categorize them and associate usual J2EE component types to them as shown in Table 1.

Service Communication Interfaces
In SOA systems, service interfaces are even more important than service implementations, because interoperability essentially depends on the communication technologies supported by the service interfaces. Remember one of the founding principles of service architecture: the service implementation is separated from the service interface(s).

To continue this discussion, we'll distinguish between "internal" and "external" clients. A client is internal if the organization controls the network path between the client and the service. In all other cases the client is external. This distinction is driven by the fact that firewalls might be located between the external client and the service, and no assumption can be made on which ports the firewall keeps open and which protocols the firewall lets pass, except that it allows text over HTTP. In particular, this is true if the client component is located on the Internet.

The major condition to decide on in a service interface technology is whether the service clients are internal or not. In Figure 1, external clients are red and internal clients are green. ExternalMainClient uses the Internet. As mentioned earlier, this causes severe restrictions as to which ports and protocols are available for communication. For example, communicating in RMI or IIOP is not realistic, since most firewalls will not let these protocols go through. In such a situation, only text-based protocols over HTTP (or HTTPS) should be considered.

Web services, a standardized technology that leverages the convenience of XML as text over HTTP, is the best technology available, provided that the client platform supports Web services. The .NET client from our example understands Web services. If it were not the case, we would have had to downgrade the communication to, for example, plain XML text over HTTP, with custom XML generation and parsing on the client side.

Now let's have a look at internal clients. OrderClient is a J2EE application client using RMI to communicate with OrderWorkflow. Why RMI and not Web services? Isn't Web services the most cool technology that every supporting platform should use when possible? Well, no. Using Web services between "internal" J2EE components has a heavy performance toll. Performance, which is a critical factor for most systems, is much more favorable to RMI than to Web services. It must be noted that Web services still has opportunities for significant optimizations, but current Web services implementations are notoriously slower than RMI.

The golden rule is: if a J2EE service only has internal J2EE or Java clients, stick to RMI, but if you can't make this assumption, consider Web services.This rule can be understood with a bit of logic: the closer the interface technology is to the implementation technology, the less work that has to be done to translate between the two. For example, XML, which Web services messages are made of, is farther from Java than RMI is. The gap between XML types and Java types is wider than the gap between CORBA IIOP types and Java types, which in turn is wider than the gap between RMI types and Java types. To generalize this rule, we can say that the more interoperable a technology is, the slower it tends to be. Although technology implementations can provide exceptions to this rule, the rule remains true in the vast majority of cases.

Each situation requires a decision based on the trade-off between interoperability and performance.

Fortunately, interoperability and performance benefits can be combined thanks to the fact that a service can have more than one interface. OrderWorkflow is a good example. While its implementation of the application logic is developed only once, the service presents two different interfaces: one RMI and one Web services.

Moreover, with the right tools, service interfaces can be generated automatically from one another. For example, a tool such as Castor XML or a JAXB implementation can generate Java classes from the XML Schemas. The RMI interface is thus generated with minimal hand coding. Enabling Web services as EJB endpoints is also a good alternative.

Figure 2 focuses on the OrderWorkflow service to illustrate how a single service is accessed through two communication channels. ExternalMainClient accesses the service through its Web services interface, which in terms of J2EE component types is a Web application resource (WAR). Upon receiving a Web services request, the WAR makes an ordinary Java method call to the business delegate located in the JAR, which in turn makes an RMI call to the EJB.

In contrast, the local OrderClient J2EE client directly calls the delegate without going through the WAR. The service business logic is located in the EJB-JAR component, and the WAR implements a Web services interface layer above the ordinary business delegate. Both interfaces share exactly the same business logic. This design pattern ensures a multiple-communication-channel SOA as well as the scalability, distributability, and other capabilities provided by the EJB technology.

The marketing application is a C legacy application that calls the reporting component to present statistical data to the user. Marketing is an internal client, but does not support RMI. CORBA is an effective and mature distributed architecture available to both C and J2EE platforms. Again, the reason for choosing CORBA over Web services is the performance. As a general rule, internal components should not communicate through Web services unless some other capability of Web services, such as the UDDI publish-discover mechanism, for example, is a deciding factor.

More Stories By Bruno Collet

Bruno Collet is a seasoned J2EE architect with five years of experience. He recently founded Studio 184 (www.studio184.com), where he is developing the ApolloNews news aggregator. Bruno holds a masters in computer science from ULB (Belgium), as well as several industry certifications (www.brunocollet.com).

Comments (0)

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.


@ThingsExpo Stories
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...
The 20th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held June 6-8, 2017, at the Javits Center in New York City, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Containers, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportunity. Submit your speaking proposal ...
You have great SaaS business app ideas. You want to turn your idea quickly into a functional and engaging proof of concept. You need to be able to modify it to meet customers' needs, and you need to deliver a complete and secure SaaS application. How could you achieve all the above and yet avoid unforeseen IT requirements that add unnecessary cost and complexity? You also want your app to be responsive in any device at any time. In his session at 19th Cloud Expo, Mark Allen, General Manager of...