Web Services

Web Services:

“Web services are set of standards that enable to interoperable integration between disparate process and systems, running on variety of platforms and frameworks”. 

Simple term of web services def

 Web service is a small unit of program which allows us to create client/server applications. It is yet another distributed computing technology like Corba, RMI, and EJB etc.

 It is used to access distributed resources like

• Web Services access to shared data
• Web Services access to shared program
• Web Services connect system and devices (like CPU, Memory, printer, etc.)
• Web Services provide communication between different technology applications 

Web Services are

·         Web Services platform independent.

·         Web Services language independent.

·         Web Services implementation independent.

·         Web services make application component reusable.

Web Services Architecture:

Web Service Components:

WSDL (Web Service Description Language):  it is XML based description of web services. it is used to locate and describe the web services.

SOAP (Simple Object Access Protocol): It is a protocol for accessing the web services and it is XML based structure used to send and receive the request and response of services as XML message (SOAP Message).

UDDI (Universal Description, Discovery and Integration): It is XML based registry to publish service and find the service from registry.

Web services benefits:

• Language neutrality 
• Interoperability 
• Industry support 
• Application component reusable.

                     

How can create Web Service:

We can create web services in Java using different service engine like Apache axis2 and Apache CXF.

Apache Axis2: Axis2 is a Web Services / SOAP / WSDL engine, the successor to the widely used Apache Axis SOAP stack. There are two implementations of the Apache Axis2.

More details you can refer this link http://axis.apache.org/axis2/java/core/

Apache CXF: Apache CXF is an open source services framework. CXF helps you build and develop services using frontend programming APIs, like JAX-WS and JAX-RS. These services can speak a variety of protocols such as SOAP, XML/HTTP, RESTful HTTP, or CORBA and work over a variety of transports such as HTTP, JMS or JBI.

More details you can refer this link http://cxf.apache.org/

Building Web Services:

We can implement the web services two ways by using Apache Axis2 or Apache CXF in java.  

1-Code First Services (Bottom-UP Approach).

·         First write a normal java code.

·         Expose Interface as web services.

·         WSDL would available for the client.

2-Contract First or WSDL First Services (Top-Down Approach)

·         First write a schema, xsd and wsdl file.

·         Create interface and other code using service engine from wsdl.

·         Add business logic.

·         Expose interface with business logic as web services.

·         Service would be available for client.