Welcome!

Java Authors: Roger Strukhoff, Lori MacVittie, Esmeralda Swartz, Trevor Parsons, Sandi Mappic

Related Topics: Java

Java: Article

Seam: The Next Step in the Evolution of Web Applications

A powerful new application framework for managing contextual components

Web sites were originally static. Later dynamic content came about through CGI scripts paving the way for the first true Web applications. Since HTTP was entirely stateless, it became necessary to invent ways for requests to be linked together in a sequence. At first state was added to the URLs, but later the cookie concept came into being. By giving each user a special token, the server could maintain a context for each user, the HTTP session where the application can store state. As simple as it is, the HTTP session defines the entire concept of what a Web application is today.

The benefits of the HTTP session are clear, but we don't often stop to think about the drawbacks. When we use the HTTP session in a Web application, we store the sum total of the state of the user's interaction with the application in one place. This means that unless we jump through some seriously complex hoops, the user can only interact with an application in one way at a time.

Consider an application that manages a set of paged search results stored in the HTTP session. If the user were to start a new search in a new window, the new search would overwrite any previous session-scoped results. That's painful enough, but multitasking users aren't the only way session-scoped data causes Web applications to explode.

Consider our friend the back button, the mortal enemy of nearly every Web developer. When a user goes backwards in time to a previous page and presses a button, that application invocation expects to be associated with an HTTP session state that may have subsequently changed. When your application only has one context to store state, there's little hope of creating anything but the fragile Web applications that we all struggle with.

Most applications deal with this by adding state to the URLs, either going back to manually putting state information in the URLs or by adding a cookie-like token in the URL to point to a finer-grained context than the HTTP session. This can force the developer to pay a lot of attention to state management, often spending more time on it than on writing the actual application.

JBoss Seam
This article introduces JBoss Seam, a framework for managing contextual components. You'll see how Seam can manage state information in a Web application, overcoming the fundamental limitations of the HTTP session and enabling entirely new contexts that dramatically extend the capabilities of Web applications. It does all of this while simplifying your Web application development and reducing the amount of code (and XML) you have to write.

Seam is a framework for managing contextual components. What does that mean? Let's first look at a component. They go by many names: JavaBeans, POJOs, Enterprise JavaBeans. They're Java classes that provide some type of function to your application. A Java EE application might have many kinds of components: JSF backing beans creating the Web tier, entity beans providing persistence, and session beans providing business logic. To Seam, they're all components. Seam unifies these diverse component models, letting you think of them all as simply application components.

A Quick Example
The best way to see what Seam can do is to look at some examples. These examples are derived from the Seam DVD Store application. You can see the complete application in the examples directory of the Seam distribution. We'll start with a simple EJB3 entity bean for a product.

@Entity
@Name("product")
public class Product
    implements Serializable
{
     long id;
     String title;
     String description;
     float price;

     @Id @GeneratedValue(strategy=AUTO)
     public long getId() {
       return id;
     }
     public void setId(long id) {
       this.id = id;
     }

     public String getTitle() {
       return title;
     }
     public void setTitle(String title) {
       this.title = title;
     }

     // more getters and setters.
}

This is an EJB3 entity bean, a POJO with a couple of annotations. The only thing that stands out here is the @Name annotation, which marks it as a Seam component named product. We'll see later how this affects things. For now let's move on to an application component that displays a list of all the products in the system.

@Stateful
@Name("search")
@Interceptors(SeamInterceptor.class)
public class SearchAction
     implements Search
{
     @PersistenceContext(type=EXTENDED)
     private EntityManager em;

     @Out
     private List<Product> products;

     @Factory("products")
     public void loadProducts()
     {
       products = em.createQuery("from Product p")
       .getResultList();
     }
}

This is a stateful EJB3 session bean. We've marked it as a Seam component using the @Name annotation and brought in Seam functionality with the SeamInterceptor. Ignoring the remaining Seam annotations for a moment, what we have here is a simple component that keeps track of a list of Product objects.

The loadProducts() method uses the EJB3 persistence API to load that list of products. It makes use of EJB3 dependency injection to receive an EntityManager instance from the container so that it can load the the products into the product list.

The goal of this component is to provide this list of products to the UI. The @Out annotation on the product list does this. @Out marks the list as data to be shared out to the UI.

Let's jump forward to the view. This is part of the Facelets XHTML template, but for our purposes you can think of it as a JSP file that uses the JavaServer Faces tag libraries. The dataTable tag renders the list of items in table form using the three column definitions: title, description, and price.

<h:dataTable value="#{products}" var="prod">
   <h:column>
     <f:facet name="header">title</f:facet>
     #{prod.title}
   </h:column>
   <h:column>
     <f:facet name="header">description</f:facet>
     #{prod.description}
   </h:column>
   <h:column>
     <f:facet name="header">price</f:facet>
     #{prod.price}
   </h:column>
</h:dataTable>

The search component provides the products value for the table to the view, but how does the value get populated in the view? The @Factory annotation on the loadProducts() method tells Seam that if a view needs a products value, the loadProducts() method can be used as a factory method to load the products from the database.

There's something else happening here. SearchAction is a stateful session bean, and the product's value is just part of its state. Stateful components have a lifecycle. They have to be created, kept around, and eventually destroyed. In Seam, stateful components have the lifecycle of their surrounding context. If a stateful component were session-scoped, for example, it would be stored in the HTTP session and destroyed when the HTTP session is destroyed, unless it reaches its natural end of life sooner.

We mentioned earlier that Seam has several more interesting contexts than just simple session-scoped data. Stateful components, by default, have conversational scope. A conversation is a sequence of clicks within a Web application. You can think of it as an actual conversation with part of the application. You interact with one part of the application for a few clicks and say good-bye, maybe moving on to some other part of the application.

More Stories By Norman Richards

Norman Richards is a JBoss developer living in Austin, Tx. He is co-author of JBoss: A Developer's Notebook and XDoclet in Action.

Comments (1)

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
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In his session at Internet of @ThingsExpo, James Kirkland, Chief Architect for the Internet of Things and Intelligent Systems at Red Hat, will describe how to revoluti...
The Internet of Things will greatly expand the opportunities for data collection and new business models driven off of that data. In her session at Internet of @ThingsExpo, Esmeralda Swartz, CMO of MetraTech, will discuss how for this to be effective you not only need to have infrastructure and operational models capable of utilizing this new phenomenon, but increasingly service providers will need to convince a skeptical public to participate. Get ready to show them the money! Speaker Bio: Esmeralda Swartz, CMO of MetraTech, has spent 16 years as a marketing, product management, and busin...
Samsung VP Jacopo Lenzi, who headed the company's recent SmartThings acquisition under the auspices of Samsung's Open Innovaction Center (OIC), answered a few questions we had about the deal. This interview was in conjunction with our interview with SmartThings CEO Alex Hawkinson. IoT Journal: SmartThings was developed in an open, standards-agnostic platform, and will now be part of Samsung's Open Innovation Center. Can you elaborate on your commitment to keep the platform open? Jacopo Lenzi: Samsung recognizes that true, accelerated innovation cannot be driven from one source, but requires a...
SYS-CON Events announced today that Red Hat, the world's leading provider of open source solutions, will exhibit at Internet of @ThingsExpo, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Red Hat is the world's leading provider of open source software solutions, using a community-powered approach to reliable and high-performing cloud, Linux, middleware, storage and virtualization technologies. Red Hat also offers award-winning support, training, and consulting services. As the connective hub in a global network of enterprises, partners, a...
P2P RTC will impact the landscape of communications, shifting from traditional telephony style communications models to OTT (Over-The-Top) cloud assisted & PaaS (Platform as a Service) communication services. The P2P shift will impact many areas of our lives, from mobile communication, human interactive web services, RTC and telephony infrastructure, user federation, security and privacy implications, business costs, and scalability. In his session at Internet of @ThingsExpo, Robin Raymond, Chief Architect at Hookflash Inc., will walk through the shifting landscape of traditional telephone a...
BSQUARE is a global leader of embedded software solutions. We enable smart connected systems at the device level and beyond that millions use every day and provide actionable data solutions for the growing Internet of Things (IoT) market. We empower our world-class customers with our products, services and solutions to achieve innovation and success. For more information, visit www.bsquare.com.
SYS-CON Events announced today that Matrix.org has been named “Silver Sponsor” of Internet of @ThingsExpo, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Matrix is an ambitious new open standard for open, distributed, real-time communication over IP. It defines a new approach for interoperable Instant Messaging and VoIP based on pragmatic HTTP APIs and WebRTC, and provides open source reference implementations to showcase and bootstrap the new standard. Our focus is on simplicity, security, and supporting the fullest feature set.
How do APIs and IoT relate? The answer is not as simple as merely adding an API on top of a dumb device, but rather about understanding the architectural patterns for implementing an IoT fabric. There are typically two or three trends: Exposing the device to a management framework Exposing that management framework to a business centric logic • Exposing that business layer and data to end users. This last trend is the IoT stack, which involves a new shift in the separation of what stuff happens, where data lives and where the interface lies. For instance, it’s a mix of architectural style...
SYS-CON Events announced today that SOA Software, an API management leader, will exhibit at SYS-CON's 15th International Cloud Expo®, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. SOA Software is a leading provider of API Management and SOA Governance products that equip business to deliver APIs and SOA together to drive their company to meet its business strategy quickly and effectively. SOA Software’s technology helps businesses to accelerate their digital channels with APIs, drive partner adoption, monetize their assets, and achieve a...
From a software development perspective IoT is about programming "things," about connecting them with each other or integrating them with existing applications. In his session at @ThingsExpo, Yakov Fain, co-founder of Farata Systems and SuranceBay, will show you how small IoT-enabled devices from multiple manufacturers can be integrated into the workflow of an enterprise application. This is a practical demo of building a framework and components in HTML/Java/Mobile technologies to serve as a platform that can integrate new devices as they become available on the market.
SYS-CON Events announced today that Utimaco will exhibit at SYS-CON's 15th International Cloud Expo®, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Utimaco is a leading manufacturer of hardware based security solutions that provide the root of trust to keep cryptographic keys safe, secure critical digital infrastructures and protect high value data assets. Only Utimaco delivers a general-purpose hardware security module (HSM) as a customizable platform to easily integrate into existing software solutions, embed business logic and build s...
Connected devices are changing the way we go about our everyday life, from wearables to driverless cars, to smart grids and entire industries revolutionizing business opportunities through smart objects, capable of two-way communication. But what happens when objects are given an IP-address, and we rely on that connection, sometimes with our lives? How do we secure those vast data infrastructures and safe-keep the privacy of sensitive information? This session will outline how each and every connected device can uphold a core root of trust via a unique cryptographic signature – a “bir...
Internet of @ThingsExpo Silicon Valley announced on Thursday its first 12 all-star speakers and sessions for its upcoming event, which will take place November 4-6, 2014, at the Santa Clara Convention Center in California. @ThingsExpo, the first and largest IoT event in the world, debuted at the Javits Center in New York City in June 10-12, 2014 with over 6,000 delegates attending the conference. Among the first 12 announced world class speakers, IBM will present two highly popular IoT sessions, which will take place November 4-6, 2014 at the Santa Clara Convention Center in Santa Clara, Calif...
Almost everyone sees the potential of Internet of Things but how can businesses truly unlock that potential. The key will be in the ability to discover business insight in the midst of an ocean of Big Data generated from billions of embedded devices via Systems of Discover. Businesses will also need to ensure that they can sustain that insight by leveraging the cloud for global reach, scale and elasticity.
WebRTC defines no default signaling protocol, causing fragmentation between WebRTC silos. SIP and XMPP provide possibilities, but come with considerable complexity and are not designed for use in a web environment. In his session at Internet of @ThingsExpo, Matthew Hodgson, technical co-founder of the Matrix.org, will discuss how Matrix is a new non-profit Open Source Project that defines both a new HTTP-based standard for VoIP & IM signaling and provides reference implementations.

SUNNYVALE, Calif., Oct. 20, 2014 /PRNewswire/ -- Spansion Inc. (NYSE: CODE), a global leader in embedded systems, today added 96 new products to the Spansion® FM4 Family of flexible microcontrollers (MCUs). Based on the ARM® Cortex®-M4F core, the new MCUs boast a 200 MHz operating frequency and support a diverse set of on-chip peripherals for enhanced human machine interfaces (HMIs) and machine-to-machine (M2M) communications. The rich set of periphera...

SYS-CON Events announced today that Aria Systems, the recurring revenue expert, has been named "Bronze Sponsor" of SYS-CON's 15th International Cloud Expo®, which will take place on November 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Aria Systems helps leading businesses connect their customers with the products and services they love. Industry leaders like Pitney Bowes, Experian, AAA NCNU, VMware, HootSuite and many others choose Aria to power their recurring revenue business and deliver exceptional experiences to their customers.
The Internet of Things (IoT) is going to require a new way of thinking and of developing software for speed, security and innovation. This requires IT leaders to balance business as usual while anticipating for the next market and technology trends. Cloud provides the right IT asset portfolio to help today’s IT leaders manage the old and prepare for the new. Today the cloud conversation is evolving from private and public to hybrid. This session will provide use cases and insights to reinforce the value of the network in helping organizations to maximize their company’s cloud experience.
The Internet of Things (IoT) is making everything it touches smarter – smart devices, smart cars and smart cities. And lucky us, we’re just beginning to reap the benefits as we work toward a networked society. However, this technology-driven innovation is impacting more than just individuals. The IoT has an environmental impact as well, which brings us to the theme of this month’s #IoTuesday Twitter chat. The ability to remove inefficiencies through connected objects is driving change throughout every sector, including waste management. BigBelly Solar, located just outside of Boston, is trans...
SYS-CON Events announced today that Matrix.org has been named “Silver Sponsor” of Internet of @ThingsExpo, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Matrix is an ambitious new open standard for open, distributed, real-time communication over IP. It defines a new approach for interoperable Instant Messaging and VoIP based on pragmatic HTTP APIs and WebRTC, and provides open source reference implementations to showcase and bootstrap the new standard. Our focus is on simplicity, security, and supporting the fullest feature set.