Java Platform, Enterprise Edition

Java platform editions
Java Card Java ME (Micro) Java SE (Standard) Jakarta EE (Enterprise) JavaFX (bundled in JRE from 8 to 10 but separately for JavaFX 1.x, 2.x and 11) PersonalJava (Discontinued)
v t e

Java Enterprise Edition (Java EE), formerly Java 2 Platform, Enterprise Edition (J2EE), currently rebranded as Jakarta EE, is a set of specifications, extending Java SE 8^[1] with specifications for enterprise features such as distributed computing and web services.^[2] Java EE applications are run on reference runtimes, that can be microservices or application servers, which handle transactions, security, scalability, concurrency and management of the components it is deploying.

Java EE is defined by its specification. The specification defines APIs (application programming interface) and their interactions. As with other Java Community Process specifications, providers must meet certain conformance requirements in order to declare their products as Java EE compliant.

Examples of contexts in which Java EE referencing runtimes are used are: e-commerce, accounting, banking information systems.

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 Jakarta 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,^[3] but April 5, 2013 according to spec document. June 12, 2013 was the planned kickoff date^[4])
• Java EE 8 (August 31, 2017^[5])
• Jakarta EE 8 (September 10, 2019) - fully compatible with Java EE 8^[6]

Java EE was maintained by Oracle under the Java Community Process. On September 12, 2017, Oracle Corporation announced that it would submit Java EE to the Eclipse Foundation.^[7] The Eclipse top-level project has been named Eclipse Enterprise for Java (EE4J).^[8] The Eclipse Foundation was forced to change the name of Java EE because Oracle owns the trademark for the name "Java."^[9] On February 26, 2018, it was announced that the new name of Java EE will be Jakarta EE.^[10]

Specifications

Java EE includes several specifications that serve different purposes, like generating web pages, reading and writing from a database in a transactional way, managing distributed queues.

The Java EE APIs include several technologies that extend the functionality of the base Java SE APIs, such as Enterprise JavaBeans, connectors, servlets, JavaServer Pages and several web service technologies.

Web specifications

• Servlet: defines how to manage HTTP requests, in a synchronous or asynchronous way. It is low level and other Java EE specifications rely on it;
• WebSocket: The Java API for WebSocket specification defines a set of APIs to service WebSocket connections;
• Java Server Faces: a technology for constructing user interfaces out of components;
• Unified Expression Language (EL) is a simple language originally designed to satisfy the specific needs of web application developers. It is used specifically in Java Server Faces to bind components to (backing) beans and in Contexts and Dependency Injection to name beans, but can be used throughout the entire platform.

Web service specifications

• Java API for RESTful Web Services provides support in creating web services according to the Representational State Transfer (REST) architectural pattern;
• Java API for JSON Processing is a set of specifications to manage information encoded in JSON format;
• Java API for JSON Binding provides specifications to convert JSON information into or from Java classes;
• Java Architecture for XML Binding allows mapping XML into Java objects;
• Java API for XML Web Services can be used to create SOAP web services.

Enterprise specifications

• Contexts and Dependency Injection is a specification to provide a dependency injection container, as in Spring;
• 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.
• Java Persistence API are specifications about object-relational mapping between relation database tables and Java classes.
• Java Transaction API 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.
• Java Message Service provides a common way for Java programs to create, send, receive and read an enterprise messaging system's messages.

Other specifications

• 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.
• Batch Applications 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.
• Java EE Connector Architecture is a Java-based tool for connecting application servers and enterprise information systems (EIS) as part of enterprise application integration (EAI). 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 referencing runtimes

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 Data Access Object 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
• Sun Community Source License
• Java Research License

References

External links

• Jakarta EE
• Goncalves, Antonio (2013). Beginning Java EE 7. Apress. http://www.apress.com/us/book/9781430246268. 
• Goncalves, Antonio (2010). Beginning Java EE 6 with GlassFish 3. Apress. https://www.apress.com/us/book/9781430228899. 
• Gupta, Arun (2013). Java EE 7 Essentials. O’Reilly. http://shop.oreilly.com/product/0636920030614.do. 
• 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
• Oracle announces its plans to move Java EE to an open source foundation

0.00 (0 votes)