Java Enterprise Edition (JEE) Tutorials

Introduction

This Tutorial Series based on the "Java EE 7 Essentials" by Arun Gupta. 

JEE provides a standards-based platform for developing web and enterprise applications. These applications are typically designed as multitier applications, with a frontend tier consisting of a web framework, a middle tier providing security and transactions, and a backend tier providing connectivity to a database or a legacy system. These applications should be responsive and capable of scaling to accommodate the growth in user demand.

The Java EE platform defines APIs for different components in each tier, and also provides
some additional services such as naming, injection, and resource management that span across the platform. These components are deployed in containers that provide runtime support. Containers provide a federated view of the underlying Java EE APIs to the application components. Java EE application components never interact directly with other Java EE application components. They use the protocols and methods of the container for interacting with each other and with platform services. Interposing a container between the application components and the Java EE services allows the container to transparently inject the services required by the component, such as declarative transaction management, security checks, resource pooling, and state management. This container-based model and abstraction of resource access allows the platform to offload the developer from common infrastructure tasks.

Java EE architecture

• 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 thirdparty 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.

The main features of JEE 7

Java API for WebSocket

• Enables a WebSocket client and server endpoint to be defined declaratively via annotations on a POJO, or programmatically via interface implementation.
• Provides server-specific configuration, such as mapping that identifies a Web‐Socket endpoint in the URI space of the container, subprotocols supported by the endpoint, and extensions required by the applications.
• Offers client-specific configurations such as providing custom configuration algorithms.
• Enables packaging and deployment on JDK or web containers. 
• Allows for integration with existing Java EE technologies.

Java API for JSON Processing

• The streaming API provides a way to parse and generate JSON in a streaming fashion.
• The Object Model API creates a random-access, tree-like structure that represents the JSON data in memory.

Batch Applications for Java Platform

• Allows for description of a Batch Job using Job Specification Language defined by an XML schema. It defines a complete execution sequence of the jobs.
• Features the Batch Programming Model using interfaces, abstract classes, and field annotations.
• Offers the Chunked and Batchlet job-processing styles.

Concurrency Utilities for Java EE

• Provides concurrency capabilities to Java EE application components, without compromising container integrity.
• Defines managed objects: ManagedExecutorService, ManagedScheduledExecutorService, ContextService, and ManagedThreadFactory.

Java API for RESTful Web Services

• Offers a new Client API that can be used to access web resources and providesintegration with JAX-RS providers.
• Supports asynchronous processing in both the Client API and the Server API.
• Defines Message Filters and Entity Interceptors as extension points to customize the request/response processing on the client and server side.
• Supports new server-side content negotiation using qs factor.
• Enables declarative validation of fields, properties, and parameters injected using @HeaderParam, @QueryParam, etc. Resource classes may be annotated with constraint annotations.

Java Message Service

• Several changes have been made to make the API simpler and easier to use. For example, Connection, Session, and other objects with a close method now implement the java.lang.Autocloseable interface to allow them to be used in a Java SE 7 try-with-resources statement. New methods have been added to create a session without the need to supply redundant arguments. A new method, getBody, has been added to allow an application to extract the body directly from a Message without the need to cast it first to an appropriate subtype.
• A message producer can now specify that a message must not be delivered until after a specified time interval.
• New send methods have been added to allow an application to send messages asynchronously.
• JMS providers must now set the JMSXDeliveryCount message property.

Expression Language

• Expression Language (EL) is a specification of its own. It can be configured and used outside of a Java EE container using ELProcessor.
• The lambda syntax is now included in EL. Using lambdas, a complete set of collection operations, such as map and filter is now supported.
• In addition to the usual arithmetic and comparison operators, new operators —such as an assignment operator and string concatenation operator—have been added to make EL more expressive.

Enterprise JavaBeans

• Support for EJB 2.1, EJB QL, and JAX-RPC-based Web Service endpoints and client view is now optional.
• Enhanced message-driven beans (MDBs) contract with a no-method message listener interface to expose all public methods as message listener methods. This will allow custom Resource Adapters for future MDBs.
• EJB API Groups have been defined with clear rules for an EJB Lite Container to support other API groups. This will help define how EJB features beyond EJB Lite can be officially added to a product that does not support full Java EE Profile.
• Asynchronous session bean invocations and nonpersistent EJB Timer Service are included in EJB Lite.
• An option has been added to disable passivation of stateful session beans.

Servlets

• Defines a standard mechanism to upgrade existing HTTP connection to a different
• protocol using HttpUpgradeHandler.
• Offers nonblocking request and response processing for async servlets.
• Defines rules for which HTTP methods are covered by .

JavaServer Faces

• Faces Flow provides an encapsulation of related views/pages with applicationdefined entry and exit points.
• Resource Library Contracts enable developers to apply facelet templates to an entire application in a reusable and interchangeable manner.
• HTML5-friendly markup allows near-total control over the user experience of each individual element in the view.
• Stateless Views mean developers no longer have to save the UIComponent state. This allows applications with JavaScript components to manage the state instead of JSF doing it for them.

Java Persistence

• Database schema and tables may be generated by using javax.persistence.schema-generation.* properties.
• Unsynchronized Persistence Contexts mean a persistence context does not have to be enlisted in a transaction. Such persistence contexts can explicitly join a transaction.
• Bulk update/delete is supported via Criteria API.
• Predefined and user-defined functions can be invoked using FUNCTION.
• Stored procedures can be invoked using StoredProcedureQuery and @NamedStoredProcedureQuery.

Interceptors

• Associating interceptors using InterceptorBinding is now part of this specification, instead of CDI.
• @AroundConstruct designates an interceptor method that receives a callback when the target class constructor is invoked.
• Method-level interceptors can be extended to life-cycle callbacks, adding constructor-level interceptors.
• Priority ranges can be dedicated for ordering interceptors using interceptorbinding.

Contexts and Dependency Injection

• Allows for automatic enabling of CDI for beans with a scope annotation, and EJBs, in Java EE.
• Supports global ordering and enabling of interceptors, decorators, and alternatives using the @Priority annotation.
• Adds the @Vetoed annotation, allowing easy programmatic disabling of classes.

Bean Validation

Validation constraints can be applied to the parameters and return values of arbitrary methods and constructors.

Integration points with CDI have been increased and reworked.

The targeted group can be altered when validation cascading is happening.

Java Transaction

• @Transactional provides the application to declaratively control transaction boundaries on CDI-managed beans, as well as classes defined as managed beans by the Java EE specification, at both the class and method level where method-level annotations override those at the class level.
• @TransactionScoped is a new CDI scope that defines bean instances whose life cycle is scoped to the currently active JTA transaction.

JavaMail

• @MailSessionDefinition and @MailSessionDefintions defines MailSession to be registered with JNDI.

Java EE Connector Architecture

• Provides @AdministeredObjectDefinition, @AdministeredObjectDefintions, @ConnectorFactoryDefinition, and @ConnectorFactoryDefinitions to define a connector-administered object and factory to be registered in JNDI.