Welcome!

Industrial IoT Authors: Elizabeth White, Pat Romanski, Liz McMillan, Jeev Trika, Scott Allen

Related Topics: Java IoT, Industrial IoT, Microservices Expo, IBM Cloud, Weblogic, IoT User Interface

Java IoT: Article

Part 3 | Component Models in Java

Service Component Architecture Model

Service Component Architecture (shortly referred as SCA) is a technology for creating services from components. SCA is a set of OASIS standards and part of it is developed with the collaboration of vendors from open source community, referred as "OSOA" Open SOA. SCA helps to build systems as a collection of interconnected components. The components created in SCA communicate through the services. The advantage of SCA is its neutral component model. It allows services to be built by any language component like Java, C++, BPEL, JavaScript, Ruby, Python etc. SCA addresses two important needs of component world:

  • Complexity
  • Reusability

SCA is best suited model for distributed systems. SCA simplifies building of systems by simple assembling of components. SCA like other component model discussed in the previous sections facilitates component assembly in the middle tier - business tier of N-tier architecture. SCA has some key elements like services, components, composites and domains.

In SCA, applications are created and assembled as components. Components contain the functionality to be exposed to the clients. The functionality provided by the components is exposed as services. Multiple components in the application interact and get bounded by a mechanism called "wire". Components are connected through wire and their services are exposed through a composite.

Several open source tools/IDEs helps to develop SCA application using designer tools. The key elements in SCA are represented through some standard symbols are represented in Figure 1.

Figure 1: SCA Key Elements

 

Services
Services are the functionality provided by the components. They are intended to perform the business function. Services can be implemented in any language like Java, C# and BPEL. Service has two primary attributes:

  • Service Contract
  • Service Address

Service contract defines the methods, input parameters for the methods and the return value. Service contract can be defined in several ways. In Java, service contract is a simple interface (POJI - Plain Old Java Interface) which exposes the functionality of the components. Service contract in Java is usually an interface which can be used locally as well as remotely. The remote service contract will have SCA annotation @Remotable. In SOA world, the service contract is defined as a WSDL file. IDL is also one of the ways to define service contract.

While service contract exposes the functionality provided by the component, Service address is used by the clients to uniquely identify the service. Service address is unique per service. Reusability is achieved through the service address, because clients connect to the service through the service address.

Component
Component provides one or more services. Components contain the business logic for the functionality exposed by service contracts - interfaces. Components can be implemented in any language supported by runtime like Java, C#, BPEL, Ruby, Python etc. Components are implemented as POJOs in Java. The Java class has to implement the Java interface defined as the service contract. Component will have an associated service, optionally a reference and a property. The service is used for exposing the functionality of the component. A reference is another interface contract provided by some other component. Component's dependency on another component is resolved through reference. A property of a component is a configurable parameter which is used to change the behavior of the component dynamically during runtime (with some of its parameters being changed). In the Java class which represents the component, property is specified as an annotation and the reference is also mentioned as an annotation.

Figure 2: Component with Services, References and Properties

Composite
A composite is a XML file which is used for configuring components. The association of the component with the service and the reference is all mentioned in the composite. A composite is the main element which is used for configuring components. The XML file is written using a language called SCDL - Service Component Definition Language which is based on XML. The composite can be written as set of XML elements or can be created using the composite designer tools provided by IDEs.

Figure 3: Composite graphical representation

First a composite is defined, then components are defined as part of it. The services provided are defined as part of the component definition. A composite is used to configure more than one component.

If a component is dependent on another component, then a reference is defined on the component which has dependency. The reference is service contract of the other component. Service and reference are connected using "Wire". Wire acts as a binding element between client component and the target component. The wire binding can be defined as a local or remote binding. The wire binding reference is also configured in the composite. In the implementation, the references to other components are referred using @Reference annotation. The reference of the target component is obtained using dependency injection. The reference dependency injection can be constructor based or setter methods based or field based injection. However the field based injection is concise which is preferred.

If the component's behavior has to be changed during runtime through change in the value of the attributes,  a property can be defined on the composite.

Figure 4: Component Wiring

Domain
Components are created and configured in composite. The composite is deployed in SCA runtime environment called ‘Domain'. A SCA domain is a collection of SCA runtime instances. SCA runtime instances host components in containers. SCA domain allows composites to be deployed as a whole and also individual component. It is possible to deploy components from a composite to be deployed in different runtimes which is purely vendor specific. The domain provides the required services like resource sharing, communication and management to the components deployed in it.

SCA Component Model Example
The SCA component model can be understood with the same shopping Cart example discussed in the models discussed earlier.

Here in this example, there is only a single component called ‘CartServiceComponent'  which exposes its functionality through the CartService interface which is the service contract for the CartServiceComponent. As a first step, the service contract is defined. The CartService interface is a service contract which contains the business methods defined by the component.

package com.online.shopping.intf;

import java.util.Collection;

public interface CartService {
public void addItem(Product product, int quantity);
public Collection<Product> listItems();    
public double getTotalPrice();
public void clearCart();
}

The CartService is implemented by the class CartServiceImpl is a POJO which represents the CartServiceComponent.

package com.online.shopping.impl;

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

import com.online.shopping.intf.CartService;
import com.online.shopping.intf.Product;

public class CartServiceImpl implements CartService {
Map<Product, Integer> items = new HashMap<Product, Integer>();      
@Override
public void addItem(Product product, int quantity) {
if(items.containsKey(product)) {
quantity +=items.get(product);
}
items.put(product, quantity);
}

@Override
public Collection<Product> listItems() {
return items.keySet();
}

@Override
public double getTotalPrice() {
double totalPrice = 0;
for(Product product: items.keySet()) {
totalPrice+=product.getPrice()* items.get(product);           
}
return totalPrice;
}

@Override
public void clearCart() {
items.clear();
}

}

The service contract and the component are connected using SCA composite designer tool provided by IDEs like Eclipse. Using the tool, a composite is created named ‘Cart.composite'. The composite is an XML file which will have an associated Cart.composite_diagram which represents the composite file as a graphical representation. In the Cart composite diagram, using the component creation tool, a component is created named ‘CartServiceComponent'. A service is added to the composite named ‘CartService'.  Using the designer tool, the Java interface file is dragged and dropped on to the Service defined and the Java implementation class to the CartServiceComponent. The service is promoted using the tool (that is exposing the service for clients to consume it). The graphical representation of composite diagram is as follows:

Figure 5: SCA Component Model - Cart Component Example

The composite file contains XML code that describes the component assembly in the composite diagram.

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<sca:composite xmlns:sca="http://www.osoa.org/xmlns/sca/1.0" name="Cart" targetNamespace="http://eclipse.org/SCACart/Cart">
<sca:component name="CartServiceComponent">
<sca:implementation.java
class="com.online.shopping.impl.CartServiceImpl"/>

<sca:service name="CartService">
<sca:interface.java
interface="com.online.shopping.intf.CartService"/>
</sca:service>

</sca:component>

<sca:service name="CartService"         
promote="CartServiceComponent/CartService"/>

</sca:composite>

The CartServiceComponent is created and assembled. The component is deployed in SCADomain as a single component with the id ‘CartService'. This is evident from the <sca:service> element having an attribute called ‘promote' in the composite XML file. The SCADomain is the runtime for the SCA components. In this example, Apache Tuscany is the runtime used for deploying composite. The client for the CartServiceComponent first looks up for the composite in the SCADomain where it is deployed. From the domain, client looks for the service with the service address and the service contract. Once it gets the service reference, the client consumes the methods exposed by the component.

package com.client.shopping;

import java.util.Collection;

import org.apache.tuscany.sca.host.embedded.SCADomain;

import com.online.shopping.intf.CartService;
import com.online.shopping.intf.Product;

public class CartClient {

public static void main(String arg[]) {
SCADomain scaDomain = SCADomain.newInstance("Cart.composite");
CartService cartService = scaDomain.getService(
CartService.class, "CartServiceComponent");

Product product = new Product();
product.setName("OSGi");
product.setPrice(550.00);
cartService.addItem(product, 20);

Product newProduct = new Product();
newProduct.setName("SCA");
newProduct.setPrice(300.00);
cartService.addItem(newProduct, 10);

Collection<Product> productItems = cartService.listItems();
for(Product items: productItems) {
System.out.println(items.getName()+"******"+ items.getPrice());             
}            

System.out.println("Total Price of Cart Items: "+cartService.getTotalPrice());

cartService.clearCart();
}
}

Thus SCA component model provides easy steps for creating and assembling components. Assembling components is easy by linking the reference to the service of the target components. SCA promotes reuse through service contracts and address and solves complexity through loose coupling. SCA as a component model promotes reusability and it is highly preferred for assembly if components. The advantage of SCA is its language neutral for several languages like Java, C#, Ruby etc.

Summary
Componentization provides several advantages. The component models play an important role in developing, deploying and assembling of components for an application. Component models provide a simpler way for component reference and look up and hence making the development easier.

In this article we discussed about four latest component models in Java - Enterprise JavaBeans, Spring, OSGi and SCA in brief. We understand that each component model has its own standards for development and assembly. The runtime environment provided by these component framework helps in execution of the components developed using the appropriate model. We also tried to understand the similarity and differences of these component models through a simple component ‘Cart' component which is part of online shopping application.

More Stories By Piram Manickam

Piram Manickam works at Infosys Limited. He would like to acknowledge and thank Sangeetha S, a beloved colleague and friend, for her invaluable contributions in this work.

More Stories By Subrahmanya SV

Subrahmanya SV works at Infosys Limited. He would like to acknowledge and thank Sangeetha S, a beloved colleague and friend, for her invaluable contributions in this work.

More Stories By S Sangeetha

S Sangeetha is a Senior Technical Architect at the E-Commerce Research Labs at Infosys Limited. She has over 15 years of experience in architecture, design and development of enterprise Java applications. She is also involved in enhancing the technical skills of Architects at Infosys. She has co-authored a book on ‘J2EE Architecture’ and also has written numerous articles on Java for various online Java forums like JavaWorld, java.net, DevX.com and internet.com. She can be reached at [email protected]

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
WebRTC adoption has generated a wave of creative uses of communications and collaboration through websites, sales apps, customer care and business applications. As WebRTC has become more mainstream it has evolved to use cases beyond the original peer-to-peer case, which has led to a repeating requirement for interoperability with existing infrastructures. In his session at @ThingsExpo, Graham Holt, Executive Vice President of Daitan Group, will cover implementation examples that have enabled ea...
Almost two-thirds of companies either have or soon will have IoT as the backbone of their business in 2016. However, IoT is far more complex than most firms expected. How can you not get trapped in the pitfalls? In his session at @ThingsExpo, Tony Shan, a renowned visionary and thought leader, will introduce a holistic method of IoTification, which is the process of IoTifying the existing technology and business models to adopt and leverage IoT. He will drill down to the components in this fra...
The Internet of Things can drive efficiency for airlines and airports. In their session at @ThingsExpo, Shyam Varan Nath, Principal Architect with GE, and Sudip Majumder, senior director of development at Oracle, will discuss the technical details of the connected airline baggage and related social media solutions. These IoT applications will enhance travelers' journey experience and drive efficiency for the airlines and the airports. The session will include a working demo and a technical d...
SYS-CON Events announced today that Pulzze Systems will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Pulzze Systems, Inc. provides infrastructure products for the Internet of Things to enable any connected device and system to carry out matched operations without programming. For more information, visit http://www.pulzzesystems.com.
SYS-CON Events announced today the Enterprise IoT Bootcamp, being held November 1-2, 2016, in conjunction with 19th Cloud Expo | @ThingsExpo at the Santa Clara Convention Center in Santa Clara, CA. Combined with real-world scenarios and use cases, the Enterprise IoT Bootcamp is not just based on presentations but with hands-on demos and detailed walkthroughs. We will introduce you to a variety of real world use cases prototyped using Arduino, Raspberry Pi, BeagleBone, Spark, and Intel Edison. Y...
Technology vendors and analysts are eager to paint a rosy picture of how wonderful IoT is and why your deployment will be great with the use of their products and services. While it is easy to showcase successful IoT solutions, identifying IoT systems that missed the mark or failed can often provide more in the way of key lessons learned. In his session at @ThingsExpo, Peter Vanderminden, Principal Industry Analyst for IoT & Digital Supply Chain to Flatiron Strategies, will focus on how IoT de...
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...
SYS-CON Events announced today that China Unicom will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. China United Network Communications Group Co. Ltd ("China Unicom") was officially established in 2009 on the basis of the merger of former China Netcom and former China Unicom. China Unicom mainly operates a full range of telecommunications services including mobile broadband (GSM, WCDMA, LTE F...
SYS-CON Events announced today that Roundee / LinearHub will exhibit at the WebRTC Summit at @ThingsExpo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. LinearHub provides Roundee Service, a smart platform for enterprise video conferencing with enhanced features such as automatic recording and transcription service. Slack users can integrate Roundee to their team via Slack’s App Directory, and '/roundee' command lets your video conference ...
DevOps at Cloud Expo, taking place Nov 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to wait for long dev...
There is growing need for data-driven applications and the need for digital platforms to build these apps. In his session at 19th Cloud Expo, Muddu Sudhakar, VP and GM of Security & IoT at Splunk, will cover different PaaS solutions and Big Data platforms that are available to build applications. In addition, AI and machine learning are creating new requirements that developers need in the building of next-gen apps. The next-generation digital platforms have some of the past platform needs a...
I'm a lonely sensor. I spend all day telling the world how I'm feeling, but none of the other sensors seem to care. I want to be connected. I want to build relationships with other sensors to be more useful for my human. I want my human to understand that when my friends next door are too hot for a while, I'll soon be flaming. And when all my friends go outside without me, I may be left behind. Don't just log my data; use the relationship graph. In his session at @ThingsExpo, Ryan Boyd, Engi...
SYS-CON Events announced today that Numerex Corp, a leading provider of managed enterprise solutions enabling the Internet of Things (IoT), will exhibit at the 19th International Cloud Expo | @ThingsExpo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Numerex Corp. (NASDAQ:NMRX) is a leading provider of managed enterprise solutions enabling the Internet of Things (IoT). The Company's solutions produce new revenue streams or create operating...
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...
Data is an unusual currency; it is not restricted by the same transactional limitations as money or people. In fact, the more that you leverage your data across multiple business use cases, the more valuable it becomes to the organization. And the same can be said about the organization’s analytics. In his session at 19th Cloud Expo, Bill Schmarzo, CTO for the Big Data Practice at EMC, will introduce a methodology for capturing, enriching and sharing data (and analytics) across the organizati...
The vision of a connected smart home is becoming reality with the application of integrated wireless technologies in devices and appliances. The use of standardized and TCP/IP networked wireless technologies in line-powered and battery operated sensors and controls has led to the adoption of radios in the 2.4GHz band, including Wi-Fi, BT/BLE and 802.15.4 applied ZigBee and Thread. This is driving the need for robust wireless coexistence for multiple radios to ensure throughput performance and th...
If you’re responsible for an application that depends on the data or functionality of various IoT endpoints – either sensors or devices – your brand reputation depends on the security, reliability, and compliance of its many integrated parts. If your application fails to deliver the expected business results, your customers and partners won't care if that failure stems from the code you developed or from a component that you integrated. What can you do to ensure that the endpoints work as expect...
Enterprise IT has been in the era of Hybrid Cloud for some time now. But it seems most conversations about Hybrid are focused on integrating AWS, Microsoft Azure, or Google ECM into existing on-premises systems. Where is all the Private Cloud? What do technology providers need to do to make their offerings more compelling? How should enterprise IT executives and buyers define their focus, needs, and roadmap, and communicate that clearly to the providers?
SYS-CON Events announced today that SoftLayer, an IBM Company, has been named “Gold Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2016, at the Javits Center in New York, New York. SoftLayer, an IBM Company, provides cloud infrastructure as a service from a growing number of data centers and network points of presence around the world. SoftLayer’s customers range from Web startups to global enterprises.
The Transparent Cloud-computing Consortium (abbreviation: T-Cloud Consortium) will conduct research activities into changes in the computing model as a result of collaboration between "device" and "cloud" and the creation of new value and markets through organic data processing High speed and high quality networks, and dramatic improvements in computer processing capabilities, have greatly changed the nature of applications and made the storing and processing of data on the network commonplace.