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Enterprise Java Beans (EJB) is a managed, server-sided component for modular construction of enterprise applications. Image File history File links Ejb. ...
Image File history File links Ejb. ...
The EJB specification is one of the several Java APIs in the Java Platform, Enterprise Edition. EJB is a server-side component that encapsulates the business logic of an application. The EJB specification was originally developed in 1997 by IBM and later adopted by Sun Microsystems (EJB 1.0 and 1.1) and enhanced under the Java Community Process as JSR 19 (EJB 2.0), JSR 153 (EJB 2.1) and JSR 220 (EJB 3.0). The Java platform is the name for a bundle of related programs, or platform, from Sun Microsystems which allow for developing and running programs written in the Java programming language. ...
API and Api redirect here. ...
Java Platform, Enterprise Edition or Java EE is a widely used platform for server programming in the Java programming language. ...
In computer networking, the term server-side refers to operations that are performed by the server in a client-server relationship. ...
International Business Machines Corporation (IBM, or colloquially, Big Blue) (NYSE: IBM) (incorporated June 15, 1911, in operation since 1888) is headquartered in Armonk, New York, USA. The company manufactures and sells computer hardware, software, and services. ...
Sun Microsystems, Inc. ...
The Java Community Process or JCP, established in 1995, is a formalized process which allows interested parties to be involved in the definition of future versions and features of the Java platform. ...
The EJB specification intends to provide a standard way to implement the back-end 'business' code typically found in enterprise applications (as opposed to 'front-end' user-interface code). Such code was frequently found to reproduce the same types of problems, and it was found that solutions to these problems are often repeatedly re-implemented by programmers. Enterprise Java Beans were intended to handle such common concerns as persistence, transactional integrity, and security in a standard way, leaving programmers free to concentrate on the particular problem at hand.
Accordingly, the EJB specification details how an application server provides: An application server is a software engine that delivers applications to client computers or devices. ...
Additionally, the Enterprise JavaBean specification defines the roles played by the EJB container and the EJBs as well as how to deploy the EJBs in a container. It has been suggested that Orthogonal persistence be merged into this article or section. ...
In computer science, transaction processing is information processing that is divided into individual, indivisible operations, called Each transaction must succeed or fail as a complete unit; it cannot remain in an intermediate state. ...
In computer science -- more specifically, in the field of databases -- concurrency control is a method used to ensure that database transactions are executed in a safe manner (i. ...
Event-driven programming is a computer programming paradigm. ...
It has been suggested that Openjms be merged into this article or section. ...
A directory service (DS) is a software application — or a set of applications — that stores and organizes information about a computer networks users and network resources, and that allows network administrators to manage users access to the resources. ...
The Java Naming and Directory Interface (JNDI) is an API for directory service that allows clients to discover and lookup data and objects via a name. ...
This article describes how security can be achieved through design and engineering. ...
Java Authentication and Authorization Service, or JAAS, pronounced Jazz, is a Java security framework for user-centric security to augment the Java code-based security. ...
Software deployment is all of the activities that make a software system available for use. ...
Software component representations: above the representation used in UML, below the representation commonly used by Microsofts COM objects. ...
Remote procedure call (RPC) is a protocol that allows a computer program running on one computer to cause a subroutine on another computer to be executed without the programmer explicitly coding the details for this interaction. ...
RMI-IIOP (read RMI over IIOP) denotes the Java RMI interface over the CORBA system. ...
The W3C defines a Web service (many sources also capitalize the second word, as in Web Services) as a software system designed to support interoperable Machine to Machine interaction over a network. ...
History
Rapid adoption followed by criticism This vision was persuasively presented by EJB advocates such as IBM and Sun Microsystems, and Enterprise JavaBeans were quickly adopted by large companies. Problems were quick to appear, however, and the reputation of EJBs began to suffer as a result. For starters, the APIs of the standard were far more complex than developers are typically used to. An abundance of checked exceptions, required interfaces, and the implementation of the bean class as an abstract class were all unusual and counter-intuitive for many programmers. Granted, the problems that the EJB standard was attempting to address, such as object-relational mapping and transactional integrity, are complex. However many programmers found the APIs to be just as difficult if not more so, leading to a widespread perception that EJBs introduced complexity without delivering real benefits. IBM redirects here. ...
Sun Microsystems, Inc. ...
API may refer to: In computing, application programming interface In petroleum industry, American Petroleum Institute In education, Academic Performance Index This page concerning a three-letter acronym or abbreviation is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...
Exception handling is a programming language construct or computer hardware mechanism designed to handle runtime errors or other problems (exceptions) which occur during the execution of a computer program. ...
Look up interface in Wiktionary, the free dictionary. ...
In object-oriented programming, a class consists of encapsulated instance variables and subprograms, the methods mentioned below. ...
Object-Relational mapping (aka O/RM, ORM, and O/R mapping) is a programming technique for converting data between incompatible type systems in databases and Object-oriented programming languages. ...
In addition, businesses found that using EJBs to encapsulate business logic brought a performance penalty. This is because the original specification only allowed for remote method invocation through CORBA (and optionally other protocols), even though the large majority of business applications actually do not require this distributed computing functionality. The EJB 2.0 specification addressed this concern by adding the concept of Local interfaces which could be called directly without performance penalties by applications that were not distributed over multiple servers. In computing, Common Object Request Broker Architecture (CORBA) is a standard for software componentry, created and controlled by the Object Management Group (OMG). ...
Distributed computing is a method of computer processing in which different parts of a program run simultaneously on two or more computers that are communicating with each other over a network. ...
The complexity issue, however, continued to hinder EJB's acceptance. Although high-quality developer tools made it easy to create and use EJBs by automating most of the repetitive tasks, these tools did not make it any easier to learn how to use the technology. Moreover, a counter-movement had grown up on the grass-roots level among programmers. The main products of this movement were the so-called 'lightweight' (i.e. in comparison to EJB) technologies of Hibernate (for persistence and object-relational mapping) and Spring Framework (which provided an alternate and far less verbose way to encode business logic). Despite their lacking the backing of big businesses that EJBs had, these technologies grew in popularity and were adopted more and more by businesses who had become disillusioned with EJBs. Hibernate is an object-relational mapping (ORM) solution for the Java language: it provides an easy to use framework for mapping an object-oriented domain model to a traditional relational database. ...
The Spring Framework (or Spring for short) is an open source application framework for the Java platform. ...
Reinventing EJBs Gradually an industry consensus emerged that the original EJB specification's primary virtue — enabling transactional integrity over distributed applications — was of limited use to most enterprise applications. The functionality delivered by simpler frameworks like Spring and Hibernate was more useful to enterprise applications. Accordingly, the EJB 3.0 specification (JSR 220) was a radical departure from its predecessors, following this new paradigm. It shows a clear influence from Spring in its use of POJOs, and its support for dependency injection to simplify configuration and integration of heterogeneous systems. Gavin King, the creator of Hibernate, participated in the EJB 3.0 process and is an outspoken advocate of the technology. Many features originally in Hibernate were incorporated in the Java Persistence API, the replacement for entity beans in EJB 3.0. The EJB 3.0 specification relies heavily on the use of annotations, a feature added to the Java language with its 5.0 release, to enable a much less verbose coding style. The Java Community Process or JCP, established in 1995, is a formalized process which allows interested parties to be involved in the definition of future versions and features of the Java platform. ...
Depending on the context Pojo refers to the Swedish name for the Finish municipality Pohja in computer science, an acronym for Plain Old Java Object. ...
Dependency injection (DI) is a programming architectural model, sometimes also referred to as inversion of control or IOC although, technically speaking, dependency injection specifically refers to an implementation of a particular form of IOC. // Dependency Injection describes the situation where one object uses a second object to provide a particular...
The Java Persistence API, sometimes referred to as JPA, is a Java programming language framework that allows developers to manage relational data in Java Platform, Standard Edition and Java Platform, Enterprise Edition applications. ...
An Entity Bean is a type of Enterprise JavaBean, a server-side Java EE component, that represents persistent data maintained in a database. ...
In computer programming, a Java annotation is a way of adding metadata to Java source code that can also be available to the programmer at run-time. ...
Accordingly, in practical terms EJB 3.0 is very nearly a completely new API, bearing little resemblance to the previous EJB specifications.
EJB types An EJB container can hold three major categories of beans: - Session Beans
- Stateless Session Beans
- Stateful Session Beans
- Entity Bean
- Container Manage Persistence.
- Bean Managed Persistence.
- Message Driven Beans (MDBs or Message Beans)
Stateless Session Beans are distributed objects that do not have state associated with them thus allowing concurrent access to the bean. The contents of instance variables are not guaranteed to be preserved across method calls. The lack of overhead to maintain a conversation with the calling program makes them less resource-intensive than stateful beans. In Java, a stateless session bean is a distributed object that does not have an associated state, thus allowing concurrent access to the bean. ...
Stateful Session Beans are distributed objects having state, that is, they keep track of which calling program they are dealing with throughout a session. For example, checking out in a web store might be handled by a stateful session bean, which would use its state to keep track of where the customer is in the checkout process. On the other hand, sending an e-mail to customer support might be handled by a stateless bean, since this is a one-off operation and not part of a multi-step process. Stateful session beans' state may be persisted, but access to the bean instance is limited to only one client. Stateful session beans are distributed objects having state. ...
Entity Beans are distributed objects having persistent state. The persistent state may or may not be managed by the bean itself. Beans in which their container manages the persistent state are said to be using Container-Managed Persistence (CMP), whereas beans that manage their own state are said to be using Bean-Managed Persistence (BMP). An Entity Bean is a type of Enterprise JavaBean, a server-side Java EE component, that represents persistent data maintained in a database. ...
Message Driven Beans are distributed objects that behave asynchronously. That is, they handle operations that do not require an immediate response. For example, a user of a website clicking on a "keep me informed of future updates" box may trigger a call to a Message Driven Bean to add the user to a list in the company's database. (This call is asynchronous because the user does not need to wait to be informed of its success or failure.) These beans subscribe to JMS (Java Message Service) message queues or message topics. They were added in the EJB 2.0 specification to allow event-driven processing inside EJB Container. Unlike other types of beans, MDB does not have a client view (Remote/Home interfaces), i.e. clients can not look-up an MDB instance. It just listens for any incoming message on a JMS queue (or topic) and processes them automatically. A Message Driven Bean (MDB) is an Enterprise Java Bean (EJB) similar to a session bean, except it responds to a JMS message rather than an RMI event. ...
It has been suggested that Openjms be merged into this article or section. ...
Other types of Enterprise Beans have been proposed. For instance, Enterprise Media Beans (JSR 86) address the integration of multimedia objects in Java EE applications. This article does not cite any references or sources. ...
Java 2 Platform, Enterprise Edition or Java EE (formerly also J2EE) is a programming platform — part of the Java platform — for developing and running distributed multi-tier architecture applications, based largely on modular components running on an application server. ...
Execution of EJBs EJBs are deployed in an EJB container within the application server. The specification describes how an EJB interacts with its container and how client code interacts with the container/EJB combination. The EJB classes used by applications are included in the javax.ejb package. (The javax.ejb.spi package is a service provider interface used only by EJB container implementations.) An application server is a software engine that delivers applications to client computers or devices. ...
Service Provider Interface (SPI) is a software mechanism to support replacable components. ...
With EJB 2.1 and earlier, each EJB had to provide a Java implementation class and two Java interfaces. The EJB container created instances of the Java implementation class to provide the EJB implementation. The Java interfaces were used by client code of the EJB. In object-oriented programming, a class is a programming language construct that is used to group related instance variables and methods. ...
The two interfaces, referred to as the Home and the Component interface, specified the signatures of the EJB's remote methods. The methods were split into two groups:
- Class methods
- Not tied to a specific instance, such as those used to create an EJB instance (factory method) or to find an existing entity EJB (see EJB Types, above). These were declared by the Home interface.
- Instance methods
- I.e. methods tied to a specific instance. These are placed in the Component interface.
Because these are merely Java interfaces and not concrete classes, the EJB container must generate classes for these interfaces that will act as a proxy in the client. Client code invokes a method on the generated proxies, which in turn places the method arguments into a message and sends the message to the EJB server. The factory method pattern is an object-oriented design pattern. ...
In object-oriented programming, a class consists of encapsulated instance variables and subprograms, the methods mentioned below. ...
Remote Communication The EJB specification requires that EJB containers support accessing the EJBs using RMI-IIOP. EJBs may be accessed from any CORBA application or provide Web Services. RMI-IIOP (read RMI over IIOP) denotes the Java RMI interface over the CORBA system. ...
In computing, Common Object Request Broker Architecture (CORBA) is a standard for software componentry, created and controlled by the Object Management Group (OMG). ...
The W3C defines a Web service (many sources also capitalize the second word, as in Web Services) as a software system designed to support interoperable Machine to Machine interaction over a network. ...
Transactions EJB containers must support both container managed ACID transactions and bean managed transactions. Container-managed transactions use a declarative syntax for specifying transactions in the deployment descriptor. For other uses, see Acid (disambiguation). ...
A transaction is an agreement, communication, or movement carried out between separate entities or objects. ...
Events JMS is used to send messages from the beans to client objects, to let clients receive asynchronous messages from these beans. MDB can be used to receive messages from client applications asynchronously using either a JMS Queue or a Topic.
Naming and Directory Services Clients of the EJB locate the Home Interface implementation object using JNDI. The Home interface may also be found using the CORBA name service. From the home interface, client code can find entity beans, as well as create and delete existing EJBs. The Java Naming and Directory Interface (JNDI) is an API for directory services. ...
Security The EJB Container is responsible for ensuring the client code has sufficient access rights to an EJB.
Deploying EJBs The EJB Specification also defines a mechanism that lets EJBs be deployed in a similar manner regardless of the specific EJB platform that is chosen. Information about how the bean should be deployed (such as the name of the Home or Remote interfaces, whether and how to store the bean in a database, etc.) are specified in the deployment descriptor. Software deployment is all of the activities that make a software system available for use. ...
The deployment descriptor is an XML document having an entry for each EJB to be deployed. This XML document specifies the following information for each EJB: A Deployment Descriptor (DD) is an XML file that describes how a web application should be deployed. ...
The Extensible Markup Language (XML) is a general-purpose markup language. ...
- Name of the Home interface
- Java class for the Bean (business object)
- Java interface for the Home interface
- Java interface for the business object
- Persistent store (only for Entity Beans)
- Security roles and permissions
- Stateful or Stateless (for Session Beans)
EJB containers from many vendors require more deployment information than that in the EJB specification. They will require the additional information as separate XML files, or some other configuration file format. An EJB platform vendor generally provides their own tools that will read this deployment descriptor, and possibly generate a set of classes that will implement the Home and Remote interfaces.
Since EJB3.0 (JSR 220), the XML descriptor is replaced by Java annotations set in the Enterprise Bean implementation (at source level), although it is still possible to use an XML descriptor instead of (or in addition to) the annotations. If an XML descriptor and annotations are both applied to the same attribute within an Enterprise Bean, the XML definition overrides the corresponding source-level annotation. In computer programming, a Java annotation is a way of adding metadata to Java source code that can also be available to the programmer at run-time. ...
Version History
EJB 3.0, final release (2006-05-02) JSR 220 - Major changes: Forget about all the pain, now it's easy to write EJBs. You just have to have a good understanding with 'annotations'. No more Home interface, Remote interface and ejb-jar.xml file. Now it only requires a business interface and a bean that implements the interface.
EJB 2.1, final release (2003-11-24) JSR 153 - Major changes: - Web service support (new): stateless session beans can be invoked over SOAP/HTTP. Also, an EJB can easily access a Web service using the new service reference.
- EJB timer service (new): Event-based mechanism for invoking EJBs at specific times.
- Message-driven beans accepts messages from sources other than JMS.
- Message destinations (the same idea as EJB references, resource references, etc.) has been added.
- EJB query language (EJB-QL) additions: ORDER BY, AVG, MIN, MAX, SUM, COUNT, and MOD.
- XML schema is used to specify deployment descriptors, replaces DTDs
The W3C defines a Web service (many sources also capitalize the second word, as in Web Services) as a software system designed to support interoperable Machine to Machine interaction over a network. ...
This article is about the computer protocol. ...
HTTP (for HyperText Transfer Protocol) is the primary method used to convey information on the World Wide Web. ...
It has been suggested that Openjms be merged into this article or section. ...
This article is about the W3Cs XML Schema language. ...
Document Type Definition (DTD), defined slightly differently within the XML and SGML (the language XML was derived from) specifications, is one of several SGML and XML schema languages, and is also the term used to describe a document or portion thereof that is authored in the DTD language. ...
EJB 2.0, final release (2001-08-22) JSR 19 - Major changes: Overall goals: - The standard component architecture for building distributed object-oriented business applications in Java.
- Make it possible to build distributed applications by combining components developed using tools from different vendors.
- Make it easy to write (enterprise) applications: Application developers will not have to understand low-level transaction and state management details, multi-threading, connection pooling, and other complex low-level APIs.
- Will follow the Write Once, Run Anywhere - philosophy of Java. An enterprise Bean can be developed once, and then deployed on multiple platforms without recompilation or source code modification.
- Address the development, deployment, and runtime aspects of an enterprise application’s life cycle.
- Define the contracts that enable tools from multiple vendors to develop and deploy components that can interoperate at runtime.
- Be compatible with existing server platforms. Vendors will be able to extend their existing products to support EJBs.
- Be compatible with other Java APIs.
- Provide interoperability between enterprise Beans and Java 2 Platform Enterprise Edition (J2EE) components as well as non-Java programming language applications.
- Be compatible with the CORBA protocols (RMI-IIOP).
“Java language†redirects here. ...
“Java language†redirects here. ...
“Java language†redirects here. ...
EJB 1.1, final release (1999-12-17) Major changes: - XML deployment descriptors
- Default JNDI contexts
- RMI over IIOP
- Security - role driven, not method driven
- Entity Bean support - mandatory, not optional
Goals for Release 1.1: - Provide better support for application assembly and deployment.
- Specify in greater detail the responsibilities of the individual EJB roles.
EJB 1.0 (1998-03-24) Announced at JavaOne 1998, Sun's third Java developers conference (March 24 through 27) Goals for Release 1.0: Attendees at the 2004 JavaOne conference described their vision of the future of Java on a whiteboard. ...
- Defined the distinct “EJB Roles” that are assumed by the component architecture.
- Defined the client view of enterprise Beans.
- Defined the enterprise Bean developer’s view.
- Defined the responsibilities of an EJB Container provider and server provider; together these make up a system that supports the deployment and execution of enterprise Beans.
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