Java Platform, Enterprise Edition

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 with specifications for enterprise features such as distributed computing and web services. 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, but April 5, 2013 according to spec document. June 12, 2013 was the planned kickoff date)
• Java EE 8 (August 31, 2017)
• Jakarta EE 8 (September 10, 2019) - fully compatible with Java EE 8

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. The Eclipse top-level project has been named Eclipse Enterprise for Java (EE4J). The Eclipse Foundation was forced to change the name of Java EE because Oracle owns the trademark for the name "Java." On February 26, 2018, it was announced that the new name of Java EE will be Jakarta EE.

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:

Specification	Java EE 6	Java EE 7	Java EE 8
Servlet	3.0	3.1	4.0
JavaServer Pages (JSP)	2.2	2.3	2.3
Unified Expression Language (EL)	2.2	3.0	3.0
Debugging Support for Other Languages (JSR-45)	1.0	1.0	1.0
JavaServer Pages Standard Tag Library (JSTL)	1.2	1.2	1.2
JavaServer Faces (JSF)	2.0	2.2	2.3
Java API for RESTful Web Services (JAX-RS)	1.1	2.0	2.1
Java API for WebSocket (WebSocket)	n/a	1.0	1.1
Java API for JSON Processing (JSON-P)	n/a	1.0	1.1
Common Annotations for the Java Platform (JSR-250)	1.1	1.2	1.3
Enterprise JavaBeans (EJB)	3.1 Lite	3.2 Lite	3.2
Java Transaction API (JTA)	1.1	1.2	1.2
Java Persistence API (JPA)	2.0	2.1	2.2
Bean Validation	1.0	1.1	2.0
Managed Beans	1.0	1.0	1.0
Interceptors	1.1	1.2	1.2
Contexts and Dependency Injection for the Java EE Platform	1.0	1.1	2.0
Dependency Injection for Java	1.0	1.0	1.0

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.

Referencing runtime	Developer	Java EE 8 certified – Full	Java EE 8 certified – Web	Java EE 7 certified – Full	Java EE 7 certified – Web	Java EE 6 certified – Full Official Oracle page for Java EE Compatibility.	Java EE 6 certified – Web	Java EE 5 certified	J2EE 1.4 certified	Licensing
GlassFish server Open Source Edition	Oracle	Yes v5.0	Yes v5.0	Yes v4.x	Yes v4.x	Yes v3.x and upward	Yes v3.x Web Profile	Yes v2.1.x		Free software
Oracle GlassFish Server	Oracle					Yes v3 based on the open source GlassFish application server		Yes Sun Java System Application Server v9.0	Yes Sun Java System Application Server v8.2	Proprietary software
Oracle WebLogic Server	Oracle			Yes 12.2.1		Yes v12c		Yes v10.3.5.0	Yes v9	Proprietary software
WildFly	Red Hat	Yes v14.x	Yes v14.x	Yes v8.1	Yes v8.0.0.Final	Yes v7.1	Yes v6.0 and v7.0	Yes v5.1	Yes v4.x	Free software
JBoss Enterprise Application Platform	Red Hat	Yes v7.2		Yes v7.0	Yes v7.0	Yes v6.0		Yes v5		Source is Free software
IBM WebSphere Application Server	IBM			Yes v9.x	Yes v9.x	Yes v8		Yes v7	Yes	Proprietary software
IBM WebSphere Application Server Liberty	IBM	Yes v18.0.0.2	Yes v18.0.0.2	Yes v8.5.5.6	Yes v8.5.5.6		Yes v8.5.5			Proprietary software
Open Liberty	IBM	Yes v18.0.0.2	Yes v18.0.0.2							Free software
IBM WebSphere Application Server Community Edition	IBM					Yes v3.0		Yes v2.1		Proprietary software
Apache Geronimo	Apache					Yes v3.0-beta-1		Yes v2.0	Yes v1.0	Free software
JEUS	TmaxSoft			Yes v8		Yes v7		Yes v6	Yes v5	Proprietary software
Cosminexus Application Server	Hitachi			Yes v10.0		Yes v9				Proprietary software
Fujitsu Interstage Application Server	Fujitsu			Yes v12.0		Yes v1 Azure/v10.1		Yes		Proprietary software
WebOTX	NEC					Yes		Yes		Proprietary software
BES Application Server	Baolande				Yes v9.5
Apache TomEE	Apache				No 7 (Java EE 7 like, but not certified)		Yes			Free software
Resin Server	Caucho						Yes v4.0		Yes	Proprietary software
Siwpas	OW2						Yes v6.0			Free software
JOnAS	OW2						Yes v5.3 rc1	Yes	Yes	Free software
SAP NetWeaver	SAP						Yes v2.x	Yes	Yes	Proprietary software
Oracle Containers for Java EE	Oracle							Yes		Proprietary software
Oracle iPlanet Web Server	Oracle								Yes Sun Java System Web Server	Proprietary software
Oracle Application Server 10g	Oracle								Yes	Proprietary software
Pramati Server	Pramati								Yes v5.0	Proprietary software
Trifork T4	Trifork								Yes	Proprietary software
Sybase Enterprise Application Server	Sybase								Yes	Proprietary software

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

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