SOA - SERVICE ORIENTED ARCHITECTURE

SOA SUPPORT IN J2EE

Platform overview
J2EE or Java EE-Java 2 Platform Enterprise Edition
Java EE is the industry standard for developing portable, robust, scalable and secure server-side Java applications. (Sun Microsystems)
Types of Platform
Java 2 Platform Standard Edition (J2SE)
Java 2 Platform Micro Edition (J2ME)
Java 2 Platform Enterprise Edition (J2EE)

Relevant layers of the J2EE platform

J2EE specifications

Java 2 Platform Enterprise Edition Specification

Java API for XML-based RPC (JAX-RPC)

Web Services for J2EE

Architecture components – Used to build J2EE web application

Java Server Pages (JSPs)

Struts

Java Servlets

Enterprise JavaBeans (EJBs)

Runtime Environments

Provides additional runtime layers & API

Support two types of Component container with JAX-RPC

EJB container

Designed to host EJB components

Provides a series of enterprise-level services

Web container

   Extension to a Web server

 Used to host Java Web applications consisting of JSP or Java servlet components.

 Provide runtime services for processing of JSP requests and servlet instances.

Programming Languages

J2EE Standard Java language can be used to build Web services.

E.g.. Rational Application developer from IBM, JDeveloper from Oracle

J2EE Programming languages are

APIs

service providers

Service Requestors

Service agents

Platform extensions

APIs

Some of the relevant APIs to building SOA are

Java API for XML Processing (JAXP)

Process XML document content using a number of available parsers.

Support Document Object Model (DOM) and Simple API for XML (SAX)

transform and validate XML documents using XSLT stylesheets and XSD schemas

Packages includes

javax.xml.parsers

org.w3c.dom & org.xml.sax

javax.xml.transform

Java API for XML-based RPC (JAX-RPC)

Most popular SOAP processing API

Support both RPC-literal, document-literal request-response exchanges and one-way transmissions

Packages

javax.xml.rpc & javax.xml.rpc.server

javax.xml.rpc.handler & javax.xml.rpc.handler.soap

javax.xml.soap & javax.xml.rpc.soap

Java API for XML Registries (JAXR)

Offers a standard interface for accessing business and service registries.

 Devp for ebXML directories, Support for UDDI.

Packages

javax.xml.registry

javax.xml.registry.infomodel

Java API for XML Messaging (JAXM)

asynchronous, document-style SOAP messaging API

Used for one-way and broadcast message transmissions

SOAP with Attachments API for Java (SAAJ)

Managing SOAP messages requiring attachments

Imp. of SOAP with Attachments (SwA) 

Java Architecture for XML Binding API (JAXB)

Generating Java classes from XSD schemas and abstracting XML-level development.

Java Message Service API (JMS)

Java-centric messaging protocol 

Providing reliable delivery features not found in typical HTTP communication.

Service Providers (SP)

Typically implemented as servlets or EJB components.

JAX-RPC Service Endpoint

Imp as a servlet by Web container logic

Used within web container

EJB Service Endpoint

 Required when runtime features only available within an EJB container

 EJB component ---Stateless Session Bean.

Service Endpoint Interface (SEI)

 Follow the JAX-RPC WSDL-to-Java mapping rules

Service Implementation Bean

A class is built by a developer to house the custom business logic of a Web service. 

The Service Implementation Bean can be imp as

 EJB Endpoint (Stateless Session Bean) 

referred to as an EJB Service Implementation Bean 

resides in the EJB container

JAX-RPC Endpoint (servlet)

called as JAX-RPC Service Implementation Bean 

deployed in the Web container.

Service Requestors (SR)

Uses JAX-RPC API to create three types of client proxies

Generated stub or (Stub)

Auto-generated by JAX-RPC compiler (at design time) by consuming SP WSDL, and producing a Java-equivalent proxy component.

 Produces a static proxy  

Dynamic proxy and dynamic invocation interface 

Actual stub is not created until its methods are           invoked at runtime

Allows for fully dynamic interaction between a Java component and a WSDL definition at runtime.

Service Agents

Perform a variety of runtime filtering, processing, and routing tasks.

E.g.. Process of SOAP header processing

JAX-RPC API allows for the creation of specialized service agents called Handlers 

Handlers can process SOAP header blocks 

 messages sent by J2EE service requestors 

 messages received by EJB and JAX-RPC Service Endpoints.

Multiple handlers process different header blocks in same 

SOAP message. (called as handler chain).

Primitive SOA support

Some primitive SOA characteristics are

Service encapsulation

Loose coupling

Messaging – via JMS protocol

JMS- Java Message service

Principles of service-orientation by J2EE

Autonomy- JAX-RPC , EJB Service Endpoints 

Reusability- service can encapsulate one or more new or existing EJB components

Statelessness- does not maintain its state

Discoverability- JAXR- represent UDDI for publishing & issuing searches

Contemporary SOA support with J2EE

Based on open standards

Supports vendor diversity

Intrinsically interoperable

Promotes federation

Architecturally composable

Extensibility

Supports service-oriented business modeling

Logic-level abstraction

Organizational agility  

Enterprise-wide loose coupling