O'Reilly Media, Inc. Enterprise JavaBeans , Sixth Edition, the image of a wallaby and .. , Sixth Edition, by Andrew Lee Rubinger and Bill Burke (O' Reilly). This repo is designed to synchronize materials between my computers. In this case, I use GitHub just like Dropbox. - slavaburdun/MyMaterials. Learn how to code, package, deploy, and test functional Enterprise JavaBeans with the latest edition of this bestselling guide. Written by the developers of JBoss .
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Enterprise JavaBeans 6th Edition – Free Pdf Book Free Books Download PDF / Free Books Online / Free eBook Download PDF / Free eBook Download. version , is covered by this, the 3rd edition of O'Reilly's EJB book. support six primary services: concurrency, transaction management, persistence. Enterprise java beans 6th edition. 1. Enterprise JavaBeans ; 2. SIXTH EDITIONEnterprise JavaBeans Andrew Lee Rubinger and Bill.
Head First EJB (Brain-Friendly Study Guides; Enterprise JavaBeans)
But it's still a complex technology that requires study and lots of practice to master. Enterprise JavaBeans 3. You'll find a straightforward, no-nonsense explanation of the underlying technology, including Java classes and interfaces, the component model, and the runtime behavior of EJB. Stay ahead with the world's most comprehensive technology and business learning platform. With Safari, you learn the way you learn best.
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View table of contents. Start reading. Book Description Learn how to code, package, deploy, and test functional Enterprise JavaBeans with the latest edition of this bestselling guide. Why Enterprise JavaBeans? Preparation Definitions Bean implementation class session and message-driven beans Bean instance session and message-driven beans Client view session and message-driven beans EJB Proxy session beans Local versus remote session beans Business interface session beans Component interface session beans Home interface session beans Endpoint interface session beans Message interface MDBs Naming Conventions Common business name Conventions for the Examples Step 2: Server-Side Component Models 5.
The death of a stateless bean instance Example: Business Interfaces Bean Implementation Class 8. Without their experience, craft, and guidance, this book would not have beenpossible. I want to thank Jason T. Greene for taking over the web services chapters. Without the earlierwork of Richard Monson-Haefel and Bill Burke, this book would not have been pos-sible. I particularly want to thank Bill for passing the baton to me on this series.
My coworkers, both within JBoss and around the community, have played no smallpart in the success of my software and this book. Carlo de Wolf, whether he likes it or not, has been the technical mentor every developershould have. Like me, he came from the community,and his dedication to our users and others in our group is noticeable every day, withoutfail, on our forums and mailing lists. You are certainly a jack of all trades. The Application Server team and members of the jboss-dev Freenode IRC Channelcomprise a support system without which my code would surely be deficient.
Our newly minted JBoss Testing team brings dedication to usability to a new level. Tim Roberts: You employed me as a college kid and let me learn open source on yourdime. It was trial by fire, and I thank you for not breaking out the extinguisher beforeI developed my chops.
Marc Elliott and Matt Warren: You gave me my first job out of school, and your pa-tience in cultivating a useful employee out of me will always be remembered. Thank you for graciously allowing me to pursue a career at JBoss. Many expert technical reviewers helped ensure that the material was technically accu-rate and true to the spirit of EJB and Java Persistence.
Of special note are Trenton D. Prelack, Fleischer, Halbert, Rudman, Clark: You locked me in a moving car and kidnapped me to a casino the weekend before myfirst draft was due.
Jonathan Adam: No brother could ever be more proud than I am of you. And you make the best bagels-n-lox breakfastknown to man. Mom and Dad, you supported me when you disagreed with me.
You whipped me intoshape when I was lazy. Thank you for being such an excellent example. Preface xxi It is a simplifiedprogramming model that, when understood at a conceptual level, has the power toeasily adapt lightweight Java classes into powerful business components. In short, EJBlets you focus on the work you do best—writing your application logic. Not only must our programs do their jobs, they must do them well.
Across the world, programmers slave over their terminals, spinningup custom solutions to the same fundamental issues facing everyone else. Bluntly put, this is a waste. Breaking Up ResponsibilitiesFor the sake of simplicity, we may categorize all code in a system into one of threeflavors: Core concernsThe primary purpose of an application is to satisfy business logic, the set of rules thatdictate its expected behavior. More simply, this is what a program does. For instance,an email client must be able to let its users read, compose, send, and organize email.
All functions related to the fulfillment of business logic fall into the category of coreconcerns. Object-oriented principles lend themselves well toward modeling business logic. In the case of our email client example,this might lead to separate modules for interacting with remote servers, renderingHTML, composing new mail, etc.
Figure Modules, each addressing one business use-case, interacting with one anotherThe core is typically going to contain rules unique to your application, and no one canbuild it aside from you and your team. Our job as software engineers is to realize ideas,so the more time we can dedicate to business logic, the more efficient we become.
Andthe best way to limit our scope to core concerns is to reduce or eliminate the energy wespend everywhere else. Cross-cutting concernsWhile the core of an application defines its primary function, there is a host of secondaryoperations necessary to keep things running correctly and efficiently.
Security asser-tions, transactional boundaries, concurrency policies—all are helpful in ensuring theintegrity of the system is in check.
enterprise javabeans 3.1 sixth edition pdf
We define these as aspects. Inother words, cross-cutting concerns are intended to stretch across modules Figure Introduction Aspects working uniformly across modulesThis layout paints a picture of perpendicular, or orthogonal, aims.
For this reason, ittakes great care to integrate aspects with the core in complementary fashion, as opposedto weighing it down. This is because they allow us to reuse shared codeacross modules, often transparently. Banking software must allow users to withdraw money from their accounts, but itwould make for an interesting solution if we could withdraw from any account wewanted; we need a security assertion at some point to ensure the requesting user haspermission.
Plumbing provides this routing, and maytake several forms: A sufficiently decoupled system defines interfaces for each module. This ensures thatcomponents may be developed in isolation, limits the need for explicit dependencies,and encourages parallel development. All good things. Plumbing code is nothing morethan an adapter between endpoints and provides few merits of its own Figure Plumbing as a connector between core concernsPerhaps the worst characteristic of the integration layer is that it is notoriously difficultto test.
Although Unit Tests, pieces of code that perform assertions on isolated func-tions, are quite easy to write given a properly designed module, Integration Tests aremuch more expansive; they typically require a more involved setup of the test envi-ronment, and they may take orders of magnitude longer to invoke. This makes for botha process prone to developer laziness tests may not be written! Plumbing is a means to an end, and therefore of little value in and of itself.
It will benefitus to take an approach that minimizes the time we spend getting data from one endpointto another. To state the obvious, the more that can be done for us, the less we have to do ourselves. On the contrary,if aspects and plumbing are provided in a generic fashion, the developer is freed to limitboth scope and focus to more tangible requirements. Check that we have permission to register someone new Security 2.
Start a boundary so everything is ensured to complete together, without affecting anything else Transactions 3.
Get a business worker delegate from some pool or cache, so we have control over concurrency Performance and Transactional Isolation 4. Make a hook into the database Resource Management 5. Store the user Business Logic 6. Email a confirmation Business Logic 8. Return our worker so another call may use it Performance and Transactional Isolation 9. Acommonly employed technique is to take advantage of a construct called a Container.
Loosely defined: A Container is a host that provides services to guest applications. The Problem Domain 7 The intent here is to provide generic services upon which applications may rely. Theservice support desired is usually defined by some combination of user code andmetadata that together follow a contract for interaction between the application andcontainer. This page docu-ment is the result of lessons learned in the field, requests by the community, and sub-sequent debate by the JSR Expert Group http: It is the purpose of this book to introduce concepts provided by the spec in a concisemanner, alongside examples where appropriate.
The Specification defines itself EJB 3. The Enterprise JavaBeans architecture is a [sic] architecture for the development and deployment of component-based business applications.
Applications written using the Enterprise JavaBeans architecture are scalable, transactional, and multi-user secure. These applications may be written once, and then deployed on any server platform that supports the Enterprise JavaBeans specification. More simply rewritten: Enterprise JavaBeans is a standard server-side component model for distributed business applications. This means that EJB defines a model for piecing together a full system by integratingmodules.
Each component may represent a collection of business processes, and thesewill run centralized on the server Figure Modules operating inside a runtime containerFigure Using runtime containers to abstract the physical location of codeEmbracing the standard of EJB has other, nontechnical benefits.
Applications that takeadvantage of EJB architecture are portable across any compliant Container implemen-tation. Finally, the familiarity of EJB means that developers already oriented to the technologymay spend less time learning the control flow of a particular application, making hiringand training a much more simplified exercise.
The Problem Domain 9 When we focus these principleson business logic, we end up with a set of business objects that encapsulate the rules ofthe road. Starting with the 3. Now we can create class hierarchies however we see fit, and reuseour objects in some non-EJB environment perhaps for quick testing outside of theContainer.
Deployed 3. Accessed via the ContainerThis is an important distinction. Server-Side Component TypesServer-side component types reside exclusively on the server, and the client must in-teract with them via some indirection. There are two major server-side componenttypes: They take action, and they frequentlycontain business methods. This means that the clientdoes not access the EJB directly, which allows the Container to perform all sorts ofmagic before a request finally hits the target method.
In truth, the client is invoking upon a proxy reference thatwill delegate the request along to the Container and return the appropriate response see Figure Stateless session beans SLSBs Stateless session beans are useful for functions in which state does not need to be carriedfrom invocation to invocation. A client cannot assume that subsequent requests will12 Chapter 2: Component Types In fact, the Container will often create and destroyinstances however it feels will be most efficient see Figure This allows theContainer to hold a much smaller number of objects in service, hence keeping memoryfootprint down.
One caveat to beware: Particular care must be employed toassure that any shared members instance variables, for instance are not leaked be-tween invocations; this may lead to unpredictable behavior. If we were to give our casino a game of roulette, SLSB would be a natural implemen-tation choice.
Roulette is a game with no memory—each spin operates independentlyfrom the last—so a function getSpinResult should return a random spot on the wheel. Stateful session beans SFSBs Stateful session beans differ from SLSBs in that every request upon a given proxy ref-erence is guaranteed to ultimately invoke upon the same bean instance.
This is to say,SFSB invocations share conversational state.
Each SFSB proxy object has an isolatedsession context, so calls to one session will not affect another. Stateful sessions, and their corresponding bean instances, are created sometime beforethe first invocation upon a proxy is made to its target instance Figure They liveuntil the client invokes a method that the bean provider has marked as a remove event,or until the Container decides to evict the session usually due to some timeout, thoughthe spec leaves this out-of-scope and up to the vendor.
Server-Side Component Types 13 Stateful session bean creating and using the correct client instance, which lives inside theEJB Container, to carry out the invocationIn order to minimize the number of stateful sessions carried around in memory, theContainer may passivate a SFSB bean instance.
No casino is complete without a good game of poker, and we could build ours usingSFSBs. Each game is played using a single deck, and we need to keep track of whichcards have already been dealt—otherwise we risk giving the player next to us the im-possible hand of five aces!
If each table is scoped to its own stateful session, we couldensure that the integrity of the deck is intact.
The singleton session bean may be marked to eagerly load when an application is de-ployed; therefore, it may be leveraged to fire application lifecycle events. This draws arelationship where deploying a singleton bean implicitly leads to the invocation of itslifecycle callbacks. If wemodel the boss as a singleton, all requests are passed along to the same source—one14 Chapter 2: Conceptual diagram of a singleton session bean with only one backing bean instanceable to make informed, consistent decisions.
Message-Driven Beans MDBs Asynchronous messaging is a paradigm in which two or more applications communi-cate via a message describing a business event.
The message-driven bean, in turn, is a listener that consumes messages and mayeither handle them directly or delegate further processing to other EJB components. The asynchronous characteristic of this exchange means that a message sender is notwaiting for a response, so no return to the caller is provided Figure Asynchronous invocation of a message-driven bean, which acts as a listener for incomingeventsOne common provider of asynchronous messaging is the Java Message Service JMS ,and the EJB specification dictates that JMS is supported implicitly.
Any instance may be used in servicinga message. In fact, the client has no view or knowledge of the MDB at all! After a full night of gambling, visitors to our casino are likely to need their cars backfrom the valet. We may provide our valet service via MDBs; once a ticket message isreceived, the valet should fetch the car while its owner continues on to grab a cup ofcoffee or visit the gift shop.
The casino visitor will have to frequently check back to seewhether his car has arrived. Message-driven beans are explored in Chapter 8. Entity BeansWhile session beans are our verbs, entity beans are the nouns. Like session beans, the entity type is modeled as a POJO, and becomes a managedobject only when associated with a construct called thejavax.
EntityManager, a container-supplied service that tracks statechanges and synchronizes with the database as necessary.
A client who alters the stateof an entity bean may expect any altered fields to be propagated to persistent storage. Frequently the EntityManager will cache both reads and writes to transparently stream-line performance, and may enlist with the current transaction to flush state to persistentstorage automatically upon invocation completion Figure Instead, they are a view that may be detached from management and used16 Chapter 2: When detached disassociated from the EntityManager ,there is no database association, but the object may later be re-enlisted with theEntityManager such that its state may again be synchronized.
Just as session beans areEJBs only within the context of the Container, entity beans are managed only whenregistered with the EntityManager. In all other cases entity beans act as POJOs, makingthem extremely versatile. Users familiar with EJB 2. Althoughentity bean classes were once required to implement specific interfaces and their call-back methods explicitly, these restrictions have been removed as of the 3. Our casino exists primarily to move money. Taking bets, paying winners, makingchange—all are transactions that need to be recorded for bookkeeping purposes.
Bymodeling currency as an entity bean, all functions that interact with cash and chipsmay share the same object view that ultimately will be preserved in the database forfuture auditing. Entity beans are introduced in Part III. EJBs may become equipped with thefacilities defined by JPA, such that modifying the properties of a managed object willbe reflected automatically in the backing database.
By exposing the database as objects to the developer, backing rows may bequeried, loaded, updated, or removed without explicitly having to go through a con-tracted API or language such as SQL. A trip to the supermarket may involve ordering sliced meats from the delicounter, selecting grocery items from pre-stacked shelves, listening to advice from thebutcher, and paying the cashier. The benefits of allowing each concern to be fulfilled by a specialist through division oflabor are fairly obvious: Similarly, application developers should write the rules of their busi-ness and leave the mechanics of reliable, distributed systems to middleware providers.
In the case of EJB, the Component Model defines our interchangeable parts, and theContainer Services are specialists that perform work upon them. The Specificationprovides: Dependency Injection DI A component-based approach to software design brings with it the complication ofinter-module communication.
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Tightly coupling discrete units together violates moduleindependence and separation of concerns, while using common lookup code leads tothe maintenance of more plumbing. In pseudocode, this looks like: UserModule may not deploy until this dependency is satisfied.
The container will populate this field during deployment. ConcurrencyAssuming each Service is represented by one instance, dependency injection alone is afine solution for a single-threaded application; only one client may be accessing a re-source at a given time. However, this quickly becomes a problem in situations wherea centralized server is fit to serve many simultaneous requests. Deadlocks, livelocks,and race conditions are some of the possible nightmares arising out of an environmentin which threads may compete for shared resources.
These are hard to anticipate, harderto debug, and are prone to first exposing themselves in production! EJB allows the applicationdeveloper to sidestep the problem entirely thanks to a series of concurrency policies.
That said, there are a series of effects upon performance to consider, so the specificationallows for configuration in some cases. If the service was restricted to a singularinstance, all subsequent requests would have to queue up until their turn was reached see Figure My experience with this enterprise software miraculously made me marketable enough to snag a post-college job in the middle of the dot-com fallout, and during my tenure there we enrolled in a weeklong training session from the source—JBoss, Inc.
The Enterprise JavaBeans architecture is a [sic] architecture for the development and deployment of component-based business applications. In pseudocode, this looks like: Finally, the familiarity of EJB means that developers already oriented to the technology may spend less time learning the control flow of a particular application, making hiring and training a much more simplified exercise.
It meant writing the programs I wanted to build, not the mechanics underneath.
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