Java Platform, Enterprise Edition

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Java Platform, Enterprise Edition (Java EE), formerly known as Java 2 Platform, Enterprise Edition (J2EE), is a computing platform for development and deployment of enterprise software (network and web services).^[1] The platform uses the object-oriented Java programming language. It is part of the Java software platform family. Java EE extends the Java Platform, Standard Edition (Java SE),^[2] providing an API for object-relational mapping, distributed and multitier architectures, and web services. The platform incorporates a design based largely on modular components running on an application server. The platform emphasizes convention over configuration^[3] and annotations for configuration. Optionally XML can be used to override annotations or to deviate from the platform defaults.

Java EE is developed under the Java Community Process.

Version history

The platform was known as Java 2 Platform, Enterprise Edition or J2EE from version 1.2, until the name was changed to Java Platform, Enterprise Edition or Java EE in version 1.5. The current version is called Java EE 8.

• J2EE 1.2 (December 12, 1999)
• J2EE 1.3 (September 24, 2001)
• J2EE 1.4 (November 11, 2003)
• Java EE 5 (May 11, 2006)
• Java EE 6 (December 10, 2009)
• Java EE 7 (May 28, 2013,^[4] but April 5, 2013 according to spec document. June 12, 2013 was the planned kickoff date^[5])
• Java EE 8 (expected by the end of 2017^[6])

Standards and specifications

Java EE is defined by its specification. As with other Java Community Process specifications, providers must meet certain conformance requirements in order to declare their products as Java EE compliant.

Java EE includes several API specifications, such as RMI, e-mail, JMS, web services, XML, etc., and defines how to coordinate them. Java EE also features some specifications unique to Java EE for components. These include Enterprise JavaBeans, connectors, servlets, JavaServer Pages and several web service technologies. This allows developers to create enterprise applications that are portable and scalable, and that integrate with legacy technologies. A Java EE application server can handle transactions, security, scalability, concurrency and management of the components it is deploying, in order to enable developers to concentrate more on the business logic of the components rather than on infrastructure and integration tasks.

General APIs

The Java EE APIs includes several technologies that extend the functionality of the base Java SE APIs.

javax/servlet

The servlet specification defines a set of APIs to service mainly HTTP requests. It includes the JavaServer Pages (JSP) specification.

javax/websocket

The Java API for WebSocket specification defines a set of APIs to service WebSocket connections.

javax/faces

This package defines the root of the JavaServer Faces (JSF) API. JSF is a technology for constructing user interfaces out of components.

javax/faces/component

This package defines the component part of the JavaServer Faces API. Since JSF is primarily component oriented, this is one of the core packages. The package overview contains a UML diagram of the component hierarchy.

javax/el

This package defines the classes and interfaces for Java EE's Expression Language. The Expression Language (EL) is a simple language originally designed to satisfy the specific needs of web application developers. It is used specifically in JSF to bind components to (backing) beans and in CDI to name beans, but can be used throughout the entire platform.

javax/enterprise/inject

These packages define the injection annotations for the Contexts and Dependency Injection (CDI) APIs.

javax/enterprise/context

These packages define the context annotations and interfaces for the Contexts and Dependency Injection (CDI) API.

javax/ejb

The Enterprise JavaBean (EJB) specification defines a set of lightweight APIs that an object container (the EJB container) will support in order to provide transactions (using JTA), remote procedure calls (using RMI or RMI-IIOP), concurrency control, dependency injection and access control for business objects. This package contains the Enterprise JavaBeans classes and interfaces that define the contracts between the enterprise bean and its clients and between the enterprise bean and the ejb container.

javax/validation

This package contains the annotations and interfaces for the declarative validation support offered by the Bean Validation API. Bean Validation provides a unified way to provide constraints on beans (e.g. JPA model classes) that can be enforced cross-layer. In Java EE, JPA honors bean validation constraints in the persistence layer, while JSF does so in the view layer.

javax/persistence

This package contains the contracts between a persistence provider and the managed classes and the clients of the Java Persistence API (JPA).

javax/transaction

This package provides the Java Transaction API (JTA) that contains the interfaces and annotations to interact with the transaction support offered by Java EE. Even though this API abstracts from the really low-level details, the interfaces are also considered somewhat low-level and the average application developer in Java EE is either assumed to be relying on transparent handling of transactions by the higher level EJB abstractions, or using the annotations provided by this API in combination with CDI managed beans.

javax/security/auth/message

This package provides the core of the Java Authentication SPI (JASPIC) that contains the interfaces and classes to build authentication modules for secure Java EE applications. Authentication modules are responsible for the interaction dialog with a user (e.g. redirecting to a Form or to an OpenID provider), verifying the user's input (e.g. by doing an LDAP lookup, database query or contacting the OpenID provider with a token) and retrieving a set of groups/roles that the authenticated user is in or has (e.g. by again doing an LDAP lookup or database query).

javax/enterprise/concurrent

This package provides the interfaces for interacting directly with Java EE's platform default managed thread pool. A higher-level executor service working on this same thread pool can be used optionally. The same interfaces can be used for user-defined managed thread pools, but this relies on vendor specific configuration and is not covered by the Java EE specification.

javax/jms

This package defines the Java Message Service (JMS) API. The JMS API provides a common way for Java programs to create, send, receive and read an enterprise messaging system's messages.

javax/batch/api

This package defines the entry AP for Java EE Batch Applications. The Batch Applications API provides the means to run long running background tasks that possibly involve a large volume of data and which may need to be periodically executed.

javax/resource

This package defines the Java EE Connector Architecture (JCA) API. Java EE Connector Architecture (JCA) is a Java-based technology solution for connecting application servers and enterprise information systems (EIS) as part of enterprise application integration (EAI) solutions. This is a low-level API aimed at vendors that the average application developer typically does not come in contact with.

Web profile

In an attempt to limit the footprint of web containers, both in physical and in conceptual terms, the web profile was created, a subset of the Java EE specifications. The Java EE web profile comprises the following:

Certified application servers

Although by definition all Java EE implementations provide the same base level of technologies (namely, the Java EE spec and the associated APIs), they can differ considerably with respect to extra features (like connectors, clustering, fault tolerance, high availability, security, etc.), installed size, memory footprint, startup time, etc.

Code sample

The code sample shown below demonstrates how various technologies in Java EE 7 are used together to build a web form for editing a user.

In Java EE a (web) UI can be built using Servlet, JavaServer Pages (JSP), or JavaServer Faces (JSF) with Facelets. The example below uses JSF and Facelets. Not explicitly shown is that the input components use the Java EE Bean Validation API under the covers to validate constraints.

<html xmlns="http://www.w3.org/1999/xhtml" 
      xmlns:h="http://xmlns.jcp.org/jsf/html" xmlns:f="http://xmlns.jcp.org/jsf/core">

    <f:metadata>
        <f:viewParam name="user_id" value="#{userEdit.user}" converter="#{userConvertor}" />
    </f:metadata>
        
    <h:body>
                
        <h:messages />
                
        <h:form>        
            <h:panelGrid columns="2">                                  
                <h:outputLabel for="firstName" value="First name" />
                <h:inputText id="firstName" value="#{userEdit.user.firstName}" label="First name" />
                                
                <h:outputLabel for="lastName" value="Last name" />
                <h:inputText id="lastName" value="#{userEdit.user.lastName}" label="Last name"  />
                           
                <h:commandButton action="#{userEdit.saveUser}" value="Save" />
            </h:panelGrid>
        </h:form>
        
    </h:body>
</html>

Example Backing Bean class

To assist the view, Java EE uses a concept called a "Backing Bean". The example below uses Contexts and Dependency Injection (CDI) and Enterprise JavaBean (EJB).

@Named
@ViewScoped
public class UserEdit {
        
    private User user;

    @Inject
    private UserDAO userDAO;
  
    public String saveUser() {
        userDAO.save(this.user);        
        addFlashMessage("User " + this.user.getId() + " saved");
                
        return "users.xhtml?faces-redirect=true";
    }

    public void setUser(User user) {
        this.user = user;
    }

    public User getUser() {
        return user;
    }
}

Example DAO class

To implement business logic, Enterprise JavaBean (EJB) is the dedicated technology in Java EE. For the actual persistence, JDBC or Java Persistence API (JPA) can be used. The example below uses EJB and JPA. Not explicitly shown is that JTA is used under the covers by EJB to control transactional behavior.

@Stateless
public class UserDAO {
        
    @PersistenceContext
    private EntityManager entityManager;
        
    public void save(User user) {
        entityManager.persist(user);
    }
        
    public void update(User user) {
        entityManager.merge(user);
    }

    public List<User> getAll() {
        return entityManager.createNamedQuery("User.getAll", User.class)
                            .getResultList();
    }

}

Example Entity class

For defining entity/model classes Java EE provides the Java Persistence API (JPA), and for expressing constraints on those entities it provides the Bean Validation API. The example below uses both these technologies.

@Entity
public class User {

    @Id
    @GeneratedValue(strategy = IDENTITY)
    private Integer id;
        
    @Size(min = 2, message="First name too short")
    private String firstName;
        
    @Size(min = 2, message="Last name too short")
    private String lastName;
  
    public Integer getId() {
        return id;
    }
        
    public void setId(Integer id) {
        this.id = id;
    }
  
    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
        
    public String getLastName() {
        return lastName;
    }
 
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

}

See also

• Web container
• Deployment Descriptor
• Java BluePrints
• Sun Java System Portal Server
• Java EE version history
• Sun Community Source License
• Java Research License

References

External links

Wikimedia Commons has media related to Java EE.

• Oracle Technology Network's Java EE
• Oracle's Java EE Compatibility page - Certified Java EE Compatible Implementations
• Core J2EE Patterns
• A short tutorial introducing beginning Java EE developers to the Java EE platform
• Cloud Tutorial - Java EE in a Day Java EE Tutorial that embraces the use of a Cloud IDE to let you learn the fundamentals of Java EE in just one day