Enterprise Java is a highly scalable and reverse platform that is used to develop everything from small business websites to Fortune 500 backend systems. In fact, hundreds of thousands of your favorite websites are already running this ever-evolving platform. And with exciting new advancements locked into its roadmap, Enterprise Java has a bright future.

In this article, I will give you a high level overview of Java Enterprise ecosystem , and you will learn much, much more. We’ve got a lot to cover, so let’s get started.

History of JavaEE

Definition : Java EE consists of a set of over 28 specifications and a runtime environment. This means that all Java SE APIs can be used in combination with any Java EE component.

This set of APIs can be used to build standard component-based multi-tier applications and can be deployed in different containers offering a variety of services. The Java EE programming model relies on annotations to specify configurations, rather than XML description files, and uses convention over configuration to help you get up and running with as little ceremony as possible. It has its own contextually-aware dependency injection framework at the heart of its programming model.

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.

The Java EE platform is developed though the Java Community Process, JCP, which is responsible for all Java technologies. The expert group is composed of interested parties that have created Java specification requests, JSRs, to define the various Java technologies.

This is done in cooperation with international Java developer community. The work of the Java community under the JCP program helps to ensure Java technology’s standards of stability and cross-platform compatibility. Anybody can review and comment on Java specifications and JSR proposals, as well as read the JCP blog. Anyone can register as a user of the site and can self-nominate as a contributor or expert group member. You can become a JCP member yourself and make an even greater contribution.

The Java EE Guardians

The Java EE Guardians are an independent group of Java Enterprise Edition developers and evangelists that are collaborating in order to move Java EE forward. Their purpose is advocacy, raising awareness, finding solutions, and collaboration and mutual support. Please support their efforts. You can join them by visiting their website, javaee-guardians.io, and you can follow them on their Twitter handle @javaee_guardian. Once the JSR has been approved and its development finalized, it forms part of the next release of the platform.

The platform continued to grow, but at a much slower rate. With each new release, it became more programmer-friendly, and the number of APIs blossomed to reach 28-plus, from just a handful of five APIs in 1999. So what’s planned for Java EE 8? Oracle is moving Java EE’s focus to Microservices and the Cloud. And the next version of Java EE is going to include APIs that compliment this new direction. So as well as advancements to some already-established technologies such as Bean Validation, Context, and Dependency Injection, Java server faces JAX-RS, RESTful Web Services, JSON processing and servlets.

There will be four new APIs, JSON-Binding, a dedicated security API, and two APIs designed for use with Microservice’s configuration and health check. Java EE 9 will see even more APIs designed for the development of Microservices and Cloud-based applications.

A summary of all Java EE specifications

The Java EE 7 technologies

Below you will find a list of specifications for the Java EE 7 technologies. For more details, check the JSR pages:

Java EE Platform
- JSR 342: Java Platform, Enterprise Edition 7 (Java EE 7)
Web Application Technologies
- JSR 356: Java API for WebSocket
- JSR 353: Java API for JSON Processing
- JSR 340: Java Servlet 3.1
- JSR 344: JavaServer Faces 2.2
- JSR 341: Expression Language 3.0
- JSR 245: JavaServer Pages 2.3
- JSR 52: Standard Tag Library for JavaServer Pages (JSTL) 1.2
Enterprise Application Technologies
- JSR 352: Batch Applications for the Java Platform
- JSR 236: Concurrency Utilities for Java EE 1.0
- JSR 346: Contexts and Dependency Injection for Java 1.1
- JSR 330: Dependency Injection for Java 1.0
- JSR 349: Bean Validation 1.1
- JSR 345: Enterprise JavaBeans 3.2
- JSR 318: Interceptors 1.2
- JSR 322: Java EE Connector Architecture 1.7
- JSR 338: Java Persistence 2.1
- JSR 250: Common Annotations for the Java Platform 1.2
- JSR 343: Java Message Service API 2.0
- JSR 907: Java Transaction API (JTA) 1.2
- JSR 919: JavaMail 1.5
Web Services Technologies
- JSR 339: Java API for RESTful Web Services (JAX-RS) 2.0
- JSR 109: Implementing Enterprise Web Services 1.3
- JSR 224: Java API for XML-Based Web Services (JAX-WS) 2.2
- JSR 181: Web Services Metadata for the Java Platform
- JSR 101: Java API for XML-Based RPC (JAX-RPC) 1.1
- JSR 67: Java APIs for XML Messaging 1.3
- JSR 93: Java API for XML Registries (JAXR) 1.0
Management and Security Technologies
- JSR 196: Java Authentication Service Provider Interface for Containers 1.1
- JSR 115: Java Authorization Contract for Containers 1.5
- JSR 88: Java EE Application Deployment 1.2 (Optional)
- JSR 77: J2EE Management 1.1
- JSR 45: Debugging Support for Other Languages 1.0
Java EE-related Specs in Java SE
- JSR 222: Java Architecture for XML Binding (JAXB) 2.2
- JSR 206: Java API for XML Processing (JAXP) 1.3
- JSR 221: Java Database Connectivity 4.0
- JSR 3: Java Management Extensions (JMX) 2.0
- JSR 925: JavaBeans Activation Framework (JAF) 1.1
- JSR 173: Streaming API for XML (StAX) 1.0

For more details, refer to this page.

The Java EE stack

As mentioned by Arun Gupta in his book entitled Java EE 7 Essentials, the different components work together to provide an integrated stack, as shown below:

So, we have the following:

Different components can be logically divided into three tiers: backend tier, middle tier, and web tier. This is only a logical representation, and the components can be restricted to a different tier based upon the application’s requirements.
JPA and JMS provide the basic services such as database access and messaging. JCA allows connection to legacy systems. Batch is used for performing noninteractive, bulk-oriented tasks.
Managed Beans and EJB provide a simplified programming model using POJOs to use the basic services.
CDI, Interceptors, and Common Annotations provide concepts that are applicable to a wide variety of components, such as type-safe dependency injection, addressing cross-cutting concerns using interceptors, and a common set of annotations. Concurrency Utilities can be used to run tasks in a managed thread. JTA enables Transactional Interceptors that can be applied to any POJO.
CDI Extensions allow you to extend the platform beyond its existing capabilities in a standard way.
Web Services using JAX-RS and JAX-WS, JSF, JSP, and EL define the programming model for web applications. Web Fragments allow automatic registration of third-party web frameworks in a very natural way. JSON provides a way to parse and generate JSON structures in the web tier. WebSocket allows the setup of a bidirectional, full-duplex communication channel over a single TCP connection.
Bean Validation provides a standard means to declare constraints and validate them across different technologies.

A briefing of each technology

To learn more about the main technologies listed above, check the Java EE 7 tutorial. And a good overview of the main technologies can be found in this page. Just quoting it here:

Enterprise JavaBeans Technology

An Enterprise JavaBeans (EJB) component, or enterprise bean, is a body of code that has fields and methods to implement modules of business logic. You can think of an enterprise bean as a building block that can be used alone or with other enterprise beans to execute business logic on the Java EE server.

Enterprise beans are either session beans or message-driven beans.

A session bean represents a transient conversation with a client. When the client finishes executing, the session bean and its data are gone.
A message-driven bean combines features of a session bean and a message listener, allowing a business component to receive messages asynchronously. Commonly, these are Java Message Service (JMS) messages.

In the Java EE 7 platform, new enterprise bean features include the following:

Asynchronous local session beans in EJB Lite
Nonpersistent timers in EJB Lite

The Java EE 7 platform requires Enterprise JavaBeans 3.2 and Interceptors 1.2. The Interceptors specification is part of the EJB specification.

Java Servlet Technology

Java Servlet technology lets you define HTTP-specific servlet classes. A servlet class extends the capabilities of servers that host applications accessed by way of a request-response programming model. Although servlets can respond to any type of request, they are commonly used to extend the applications hosted by web servers.

In the Java EE 7 platform, new Java Servlet technology features include the following:

Nonblocking I/O
HTTP protocol upgrade

The Java EE 7 platform requires Servlet 3.1.

JavaServer Faces Technology

JavaServer Faces technology is a user interface framework for building web applications. The main components of JavaServer Faces technology are as follows:

A GUI component framework.
A flexible model for rendering components in different kinds of HTML or different markup languages and technologies. A Renderer object generates the markup to render the component and converts the data stored in a model object to types that can be represented in a view.
A standard RenderKit for generating HTML 4.01 markup.

The following features support the GUI components:

Input validation
Event handling
Data conversion between model objects and components
Managed model object creation
Page navigation configuration
Expression Language (EL)

All this functionality is available using standard Java APIs and XML-based configuration files.

In the Java EE 7 platform, new features of JavaServer Faces technology include the following:

HTML5-friendly markup
Faces Flows
Resource library contracts

The Java EE 7 platform requires JavaServer Faces 2.2 and Expression Language 3.0.

JavaServer Pages Technology

JavaServer Pages (JSP) technology lets you put snippets of servlet code directly into a text-based document. A JSP page is a text-based document that contains two types of text:

Static data, which can be expressed in any text-based format, such as HTML or XML
JSP elements, which determine how the page constructs dynamic content

For information about JSP technology, see the The Java EE 5 Tutorial at http://docs.oracle.com/javaee/5/tutorial/doc/.

The Java EE 7 platform requires JavaServer Pages 2.3 for compatibility with earlier releases but recommends the use of Facelets as the display technology in new applications.

JavaServer Pages Standard Tag Library

The JavaServer Pages Standard Tag Library (JSTL) encapsulates core functionality common to many JSP applications. Instead of mixing tags from numerous vendors in your JSP applications, you use a single, standard set of tags. This standardization allows you to deploy your applications on any JSP container that supports JSTL and makes it more likely that the implementation of the tags is optimized.

JSTL has iterator and conditional tags for handling flow control, tags for manipulating XML documents, internationalization tags, tags for accessing databases using SQL, and tags for commonly used functions.

The Java EE 7 platform requires JSTL 1.2.

Java Persistence API

The Java Persistence API (JPA) is a Java standards–based solution for persistence. Persistence uses an object/relational mapping approach to bridge the gap between an object-oriented model and a relational database. The Java Persistence API can also be used in Java SE applications outside of the Java EE environment. Java Persistence consists of the following areas:

The Java Persistence API
The query language
Object/relational mapping metadata

The Java EE 7 platform requires Java Persistence API 2.1.

Java Transaction API

The Java Transaction API (JTA) provides a standard interface for demarcating transactions. The Java EE architecture provides a default auto commit to handle transaction commits and rollbacks. An auto commit means that any other applications that are viewing data will see the updated data after each database read or write operation. However, if your application performs two separate database access operations that depend on each other, you will want to use the JTA API to demarcate where the entire transaction, including both operations, begins, rolls back, and commits.

The Java EE 7 platform requires Java Transaction API 1.2.

Java API for RESTful Web Services

The Java API for RESTful Web Services (JAX-RS) defines APIs for the development of web services built according to the Representational State Transfer (REST) architectural style. A JAX-RS application is a web application that consists of classes packaged as a servlet in a WAR file along with required libraries.

The Java EE 7 platform requires JAX-RS 2.0.

Managed Beans

Managed Beans, lightweight container-managed objects (POJOs) with minimal requirements, support a small set of basic services, such as resource injection, lifecycle callbacks, and interceptors. Managed Beans represent a generalization of the managed beans specified by JavaServer Faces technology and can be used anywhere in a Java EE application, not just in web modules.

The Managed Beans specification is part of the Java EE 7 platform specification (JSR 342). The Java EE 7 platform requires Managed Beans 1.0.

Contexts and Dependency Injection for Java EE

Contexts and Dependency Injection for Java EE (CDI) defines a set of contextual services, provided by Java EE containers, that make it easy for developers to use enterprise beans along with JavaServer Faces technology in web applications. Designed for use with stateful objects, CDI also has many broader uses, allowing developers a great deal of flexibility to integrate different kinds of components in a loosely coupled but typesafe way.

The Java EE 7 platform requires CDI 1.1.

Dependency Injection for Java

Dependency Injection for Java defines a standard set of annotations (and one interface) for use on injectable classes.

In the Java EE platform, CDI provides support for Dependency Injection. Specifically, you can use injection points only in a CDI-enabled application.

The Java EE 7 platform requires Dependency Injection for Java 1.0.

Bean Validation

The Bean Validation specification defines a metadata model and API for validating data in JavaBeans components. Instead of distributing validation of data over several layers, such as the browser and the server side, you can define the validation constraints in one place and share them across the different layers.

The Java EE 7 platform requires Bean Validation 1.1.

Java Message Service API

The Java Message Service (JMS) API is a messaging standard that allows Java EE application components to create, send, receive, and read messages. It enables distributed communication that is loosely coupled, reliable, and asynchronous.

In the platform, new features of JMS include the following.

A new, simplified API offers a simpler alternative to the previous API. This API includes a JMSContext object that combines the functions of a Connection and a Session.
All objects with a close method implement the java.lang.Autocloseable interface so that they can be used in a Java SE 7 try-with-resources statement.

The Java EE 7 platform requires JMS 2.0.

Java EE Connector Architecture

The Java EE Connector Architecture is used by tools vendors and system integrators to create resource adapters that support access to enterprise information systems that can be plugged in to any Java EE product. A resource adapter is a software component that allows Java EE application components to access and interact with the underlying resource manager of the EIS. Because a resource adapter is specific to its resource manager, a different resource adapter typically exists for each type of database or enterprise information system.

The Java EE Connector Architecture also provides a performance-oriented, secure, scalable, and message-based transactional integration of Java EE platform–based web services with existing EISs that can be either synchronous or asynchronous. Existing applications and EISs integrated through the Java EE Connector Architecture into the Java EE platform can be exposed as XML-based web services by using JAX-WS and Java EE component models. Thus JAX-WS and the Java EE Connector Architecture are complementary technologies for enterprise application integration (EAI) and end-to-end business integration.

The Java EE 7 platform requires Java EE Connector Architecture 1.7.

JavaMail API

Java EE applications use the JavaMail API to send email notifications. The JavaMail API has two parts:

An application-level interface used by the application components to send mail
A service provider interface

The Java EE platform includes the JavaMail API with a service provider that allows application components to send Internet mail.

The Java EE 7 platform requires JavaMail 1.5.

Java Authorization Contract for Containers

The Java Authorization Contract for Containers (JACC) specification defines a contract between a Java EE application server and an authorization policy provider. All Java EE containers support this contract.

The JACC specification defines java.security.Permission classes that satisfy the Java EE authorization model. The specification defines the binding of container-access decisions to operations on instances of these permission classes. It defines the semantics of policy providers that use the new permission classes to address the authorization requirements of the Java EE platform, including the definition and use of roles.

The Java EE 7 platform requires JACC 1.5.

Java Authentication Service Provider Interface for Containers

The Java Authentication Service Provider Interface for Containers (JASPIC) specification defines a service provider interface (SPI) by which authentication providers that implement message authentication mechanisms may be integrated in client or server message-processing containers or runtimes. Authentication providers integrated through this interface operate on network messages provided to them by their calling containers. The authentication providers transform outgoing messages so that the source of each message can be authenticated by the receiving container, and the recipient of the message can be authenticated by the message sender. Authentication providers authenticate each incoming message and return to their calling containers the identity established as a result of the message authentication.

The Java EE 7 platform requires JASPIC 1.1.

Java API for WebSocket

WebSocket is an application protocol that provides full-duplex communications between two peers over TCP. The Java API for WebSocket enables Java EE applications to create endpoints using annotations that specify the configuration parameters of the endpoint and designate its lifecycle callback methods.

The WebSocket API is new to the Java EE 7 platform. The Java EE 7 platform requires Java API for WebSocket 1.0.

Java API for JSON Processing

JSON is a text-based data exchange format derived from JavaScript that is used in web services and other connected applications. The Java API for JSON Processing (JSON-P) enables Java EE applications to parse, transform, and query JSON data using the object model or the streaming model.

JSON-P is new to the Java EE 7 platform. The Java EE 7 platform requires JSON-P 1.0.

Concurrency Utilities for Java EE

Concurrency Utilities for Java EE is a standard API for providing asynchronous capabilities to Java EE application components through the following types of objects: managed executor service, managed scheduled executor service, managed thread factory, and context service.

Concurrency Utilities for Java EE is new to the Java EE 7 platform. The Java EE 7 platform requires Concurrency Utilities for Java EE 1.0.

Batch Applications for the Java Platform

Batch jobs are tasks that can be executed without user interaction. The Batch Applications for the Java Platform specification is a batch framework that provides support for creating and running batch jobs in Java applications. The batch framework consists of a batch runtime, a job specification language based on XML, a Java API to interact with the batch runtime, and a Java API to implement batch artifacts.

Batch Applications for the Java Platform is new to the Java EE 7 platform. The Java EE 7 platform requires Batch Applications for the Java Platform 1.0.

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