Seam Framework: Experience the Evolution of Java EE (JBoss Series)

Seam Framework: Experience the Evolution of Java EE, 2nd Edition

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Seam also makes it easy to accomplish tasks that were "difficult" on JSF. Seam provides a number JSF component tags and annotations that would increase the "web friendliness" and web page efficiency of JSF applications. While Seam is rooted in Java EE 5. Your Seam applications can be deployed in J2EE 1. That means you can obtain production support for your Seam applications today! Seam provides its own managed stateful context that allows the frameworks to deeply integrate with others via annotations, EL Expression Language expressions etc.

That level of integration comes from Seam developer's intimate knowledge of the third party frameworks. However, most current business and web frameworks are not designed for ORM. They do not manage the persistence context over the entire web interaction lifecycle from the request comes in to the response is fully rendered.

It is designed from the ground up to promote ORM best practices. With Seam, there is no more DTOs to write; lazy loading just works; and the ORM performance can be greatly improved since the extended persistence context acts as a natural cache to reduce database round trips. Furthermore, since Seam integrates the ORM layer with the business and presentation layer, we can display ORM objects direct, you can even use database validator annotations on input forms , and redirect ORM exceptions to custom error pages.

Seam is designed for stateful web applications. Web applications are inherently multi-user applications, and e-commerce applications are inherently stateful and transactional. However, most existing web application frameworks are geared toward stateless applications.

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You have to fiddle with the HTTP session objects to manage user states. That not only clutters your application with code un-related to the core business logic, but also brings on an array of performance issues. In Seam, all the basic application components are inherently stateful. They are much easier to use than the HTTP session since their states are declaratively managed by Seam. There is no need to write distracting state management code in a Seam application -- just annotate the component with its scope, lifecycle methods, and other stateful properties -- and Seam takes over the rest.

Seam stateful components also provide much finer control over user states than the plain HTTP session does. For instance, you can have multiple "conversations", each consisting of a sequence of web requests and business method calls, in a HTTP session. Furthermore, database caches and transactions can be automatically tied with the application state in Seam.

Seam automatically holds database updates in memory and only commits to the database at the end of a conversation. The in-memory cache greatly reduces database load in complex stateful applications. In addition to all the above, Seam takes state management in web applications a big step further by supporting integration with the Open Source JBoss jBPM business process engine.

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You can now specify the work flows of different people in the organization i. Seam is fully optimized for Web 2. Internally, Seam provides an advanced concurrency model to efficiently manage multiple AJAX requests from the same user. A big challenge for AJAX applications is the increased database load.

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If all those AJAX requests have to be served by the database, the database would not be able to handle the load. The stateful persistence context in Seam acts as an in-memory cache. It can hold information throughout a long running conversation, and hence helps to reduce the database round trips.

For those sites, lazy loading in the ORM layer is crucial. Otherwise, a single query could cascade to loading the entire database. As we discussed earlier, Seam is the only web framework today that supports lazy loading correctly for web applications. Seam is a "lightweight framework" because it promotes the use of POJO plain old Java objects as service components.

There are no framework interfaces or abstract classes to "hook" components into the application. The question, of course, is how do those POJOs interact with each other to form an application? How do they interact with container services e. Under this pattern, the Seam framework manages the lifecyle of all the components.

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When a component needs to use another, it declares this dependency to Seam using annotations. Seam determines where to get this dependent component based on the application's current state and "injects" it into the asking component. Expanding on the dependency injection concept, a Seam component A can also create another component B and "outjects" the created component B back to Seam for other components, such as C, to use later. This type of bi-directional dependency management is widely used in even the simplest Seam web applications e.

In Seam terms, we call this "dependency bijection". The key design principal that makes Seam so easy to use is "Configuration by exception". The idea is to have a set of common-sense default behavior for the components. The developer only needs to configure the component explicitly when the desired behavior is not the default. For instance, when Seam injects component A as a property of component B, the Seam name of component A defaults to the recipient property name in component B.

Seam Framework: Experience the Evolution of Java EE 2nd Edition

There are many little things like that in Seam. The overall result is that configuration metadata in Seam is much simpler than competing Java frameworks. As a result, most Seam applications can be adequately configured with a small number of simple Java annotations. Developers benefit from reduced complexity and, in the end, much less lines of code for the same functionalities developed in competing frameworks. As you probably noticed, Java annotations play a crucial role in expressing and managing Seam configuration metadata. That is done by design to make the framework easier to work with.

Framework designers throw all kinds of configuration information, including Java class and method names, in XML files without much thought about the consequence to developers. In retrospect, that was a big mistake. XML configuration files are highly repetitive. They have to repeat information already in the code in order to connect the configuration to the code.

Those repetitions make the application prone to minor errors e. The lack of reasonable default configuration settings further compounds this problem. In fact, in some frameworks, the amount of boilerplate code disguised as XML may rival or even exceed the amount of actual Java code in the application. The enterprise Java community recognizes this problem with XML abuse and has very successful attempts to replace XML files with annotations in Java source code.

Why Java EE Lost and Spring Won

EJB3 is the effort by the official Java standardization body to promote the use of annotations in enterprise Java components. Seam adds to EJB3 annotations and expands the annotation-based programming model to the entire web application. Of course, XML is not entirely bad for configuration data. Seam designers recognize that XML is well-suited to specify web application pages flows or define business process work flows. The XML file allows us to centrally manage the work flow for the entire application, as opposed to scatter the information around in Java source files.

The work flow information has little coupling with the source code -- and hence the XML files do not need to duplicate typed information already available in the code. Seam is designed from ground up for easy testing. You can just create instances of the POJOs using the regular Java new keyword and then run any methods in your testing framework e. If you need to test the interaction between multiple Seam components, you can instantiate those components individually and then setup their relationships manually i.

For integrated testing of the entire Seam application, it is a little more complex since you have to run the application inside a Seam container. Seam comes with an embeddable lightweight container that helps this type of testing. In your test framework, you can load the Seam container programatically and then run the tests.

Tools support is crucial for an application framework that focuses on developer productivity. Seam is distributed with a command line application generator called Seam Gen. Seam Gen closely resembles the tools available in Ruby-On-Rails. With Seam Gen, you can get started with Seam in no time! In a nutshell, Seam simplifies the developer overhead for Java EE applications, and at the same time, adds powerful new features beyond Java EE 5. In this next section excerpted from chapter 2 in the book , we will show you some real code examples to illustrate how Seam works.

You can find the source code download for all example applications in the book from the book web site http: Seam allows seamless no pun intended! There is no more artificially required JNDI lookup, verbose JSF backing bean declaration, excessive facade business methods, and painstakingly passing objects between tiers etc. Seam eliminates those artificial requirements with annotated POJOs.

However, you are still free to use those patterns when they are truely needed in your Seam applications. Writing a Seam web application is conceptually very simple. You just need to code the following components:.

For instance, when the user clicks a button to submit a JSF form, Seam automatically parses the form fields and constructs an entity bean. Then, Seam passes the entity bean into the event handler session bean, which is also created by Seam, for processing. You do not need to manage component lifecycles and relationships between components in your own code. There is no boilerplate code and no XML file for dependency management. In this chapter, we use a hello world example to show exactly how Seam glues together a web application.

The example application works like this: The user can enter her name on a web form to "say hello" to Seam. Once she submits, the application saves her name to a relational database and displays all the users that have said hello to Seam. The example project is in the HelloWorld folder in the source code download for this book. To build it, you must have Apache ANT 1. Enter the helloworld directory and run the command ant. The JEMS installer can be downloaded from http: In this chapter, we will not spend too much time explaining the details of the directory structure in the source code project.

Instead, we focus on the code and configuration artifacts a developer must write or manage to build a Seam application. This way, you can apply the knowledge to any project structure without being confined to our template. In the book's example projects, the Java source code files are in the src directory, the web pages are in the view directory, and all configuration files are in the resources directory.

The data model in the hello world application is simply a Person class with a name and an id property. The Entity annotation tells the container to map this class to a relational database table, with each property a column in the table. Each Person instance corresponds to a row of data in the table. Since Seam is "configuration by exception", the container simply uses the class name property name for the table name and column name. The Id and GeneratedValue annotations on the id property indicates that the id column is for the primary key and its value is automatically generated by the application server for each Person object saved into the database.

The most important annotation in the Person class is the Name annotation. It specifies the string name the Person bean should be registered under Seam. In other Seam components e.

Yuan, Orshalick & Heute, Seam Framework: Experience the Evolution of Java EE, 2nd Edition | Pearson

In the JSF page, we use the Person bean to back the form input text field. Below the entry form, the JSF page displays all people who has said "hello" to Seam in the database. The list of people is stored in a Seam component named "fans". The fan symbol is the iterator for the fans list. When the user clicks on the "Say Hello" button to submit the form, Seam creates the person managed component with the input data. It then invokes the sayHello method on Seam component named "manager" i.

The manager component is an EJB3 session bean and we will discuss it in the next section. Coverage includes Using improvements to Seams conversation model, transaction management, and other features Enhancing security, performing end-to-end validation, and providing custom exception pages Using Quartz to execute timer jobs in your application Generating bookmarkable RESTful Web pages the easy way Developing highly scalable applications with Seam 2.

Nokia Smartphone Hacks Michael Juntao Yuan It wasn't long ago that owning a cell phone put you on the cusp of modern technology. Bloggat om Seam Framework: Supporting Stateful Web Applications 6 1. Convention over Configuration 8 1. Avoiding XML Abuse 8 1. Designed for Testing 9 1. Great Tools Support 10 1. Seam Hello World 11 2. Create a Data Model 13 2.

Map the Data Model to a Web Form 13 2. Handle Web Events 14 2.

Navigate to the Next Page 15 2. More on the Seam Programming Model 17 2. Configuration and Packaging 20 2. How Is This Simple? Recommended JSF Enhancements 27 3. As early as , most of the customers I worked with at JBoss were writing their applications using the Spring Framework. So we end up with another 3 year cycle of Java EE playing catch up.

And therein lies the structural problem. Quickly and easily gain access to the tools and information you need! Explore, test and combine our data quality APIs at Melissa Developer Portal — home to tools that save time and boost revenue. Over a million developers have joined DZone. Join the DZone community and get the full member experience. Some of this was underestimating Internet users. I mean, the dumb sods could never adjust to not having the trusty back button as their main means of navigation through an application, right?

As popular applications like Gmail and Facebook, among others, brought users to an AJAXy world, users adapted their behavior. They also adapted their expectations: Meanwhile, web browser JavaScript engines were making big advances in performance and even compatibility.

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