Web Services & SOAP: IT Project Requirements

• Web Services and SOAP are discussed

Requirements of an IT Project

• Functional requirements ensure applications meet business needs
• Technical requirements deal with performance metrics like response time, high availability, and scalability
• Maintenance needs include adaptability and extensibility
• Security considerations
• Portability is needed
• Distribution across systems
• Communication with distant apps is necessaary
• Service delivery to various devices, and covering software costs are factored

Development Challenges

• Building software systems that meet all requirements can be tough without using the experiences of others

Application Server Environments

• JEE application servers include JBOSS, Web Sphere, GlassFish, and Tomcat

Frameworks for Control Inversion

• Spring is a lightweight container
• EJB is a more heavy weight container

Frameworks

• Object-relational mapping tools uses PA, Hibernate, and Toplink
• Web application frameworks examples are Struts, SF, and SpringMVC

Middleware Technologies

• RMI and CORBA applications for distributed systems
• JAX WS can be leveraged for Web services using SOAP
• JAX RS is for Web services using RESTful architecture
• JMS is used for asynchronous communication between applications

HTTP Protocol Role

• Web Services use components based on Internet (HTTP), which perform dedicated tasks in a specific format (XML).
• Applications use it to remotely trigger functions, simplifying data exchange
• Web services facilitate inter-application communication across networks, independent of execution platform and implementation language
• Web Services extend initiatives such as CORBA, uses recognized tech standards, and maintains broad acceptance

HTTP Protocol Explained

• HTTP is a protocol for clients to retrieve documents from a server
• Documents can be static (HTML or PDF) or dynamically generated based on the request (PHP or JSP)
• You can submit forms
• Operations include connecting to server(socket), requesting a document, and receiving a document (status=200) or error (status =404) from server response, and disconnecting

HTTP Methods Defined

• GET retrieves the content of a document
• POST is for submitting forms, including user-entered data
• PUT uploads a file from client to server
• DELETE requests the server to remove a document
• HEAD retrieves the metadata about document with type, capacity , and time of last change

Concepts of Web Services

• Concepts are the cornerstone of many web services
• SOAP (Simple Object Access Protocol) is a platform-independent protocol for inter-application communication based on XML.
• A SOAP service call is an ASCII stream framed in XML tags and transported over HTTP.
• WSDL (Web Services Description Language) describes Web Services in XML, specifying methods, signatures, and access points (URL, port).
• WSDL is similar to IDL for distributed CORBA programming.
• UDDI (Universal Description, Discovery and Integration) standardizes distributed directories for Web Services, aiding in publication and discovery.
• UDDI acts as web service whose methods are invoked via SOAP

Cycle of Web Services

• The client finds the service, server
• the client understands and request a document
• the server uses XML contract and executes the request, and delivers output

SOAP Fundamentals

• SOAP is employed for method invocation on remote services, based on XML
• SOAP’s main goal is to facilitate inter-machine communication
• The methodology invokes RPC and sends messages to remote machines via a transport protocol e.g (HTTP)
• SOAP provides data in the forms of information retrieved form servers

SOAP Message Structure

• SOAP messages contain these parts: envelope, header, body, and fault components
• SOAP envelope forms the base
• Includes namespace and data coding specifications
• SOAP header adds decentralized functionality to SOAP messages
• Often used needing the message to be processed by intermediaries
• The SOAP body acts as container of data
• Mandates what should be expected in the final process
• The SOAP fault reports errors

JAXB Features

• It is useful to map XML to java objects
• With JAXB 2.0 objects can be mapped to JavaDoc, XML doc and vice versa
• It can generate and coordinate between JavaDoc in XML

JAXB Principles

• Mapping of document XML goes to objects
• Using document XML you can create objects

Steps to Develop Web Service with JAX-WS

• Create the service by developing and deploying the service (HTTP and WS Conteneur)
• Test your web service with analysers like Oxygen and SoapUI
• Create different clients (PHP, Java , or Net clients)