Introduction to AXIS

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Axis stands for Apache eXtensible Interaction System and is used to send and receive SOAP messages. The web service developers do not have to use SOAP directly. Axis provides API's and build tools to build SOAP services and clients.

Web service is a technology for communication between two applications. There are two parties in Axis web services

• Axis end point service: This is a SOAP Receiver
• Axis client: This is a SOAP Sender

Axis creates SOAP envelops with head, body, fault and other elements in the background while the developer is abstracted from SOAP manipulations. SOAP faults are java exceptions in Axis.

Axis2 Data Binding Frameworks

While SOAP is behind the scenes, The Axis developers need to know the data binding technologies used by Axis. While we develop the code using the below mentioned data binding Frameworks, the Axis engine internally converts the code to SOAP. However a “web service A” can be written in one data binding technique and the client written in another data binding framework can access the “web service A”. The main advantage of Axis is that it does not restrict you to use a particular data binding. The popular data binding frameworks supported by Axis are

• POJO: POJO ( Plain Old Java Object) web service is very easy to develop and understand. However it has got couple of restrictions and Spring Frame Work features need to be used to overcome these restrictions.
• AXIOM : AXIOM(AXIs Object Model) is XML based native data binding framework of AXIS. AXIOM based data binding is complex as compared to POJO as we will need to create and parse through the AXIOM trees. AXIOM gives very good performance when used for large amount of payloads.
• ADB: ADB stands for Axis2 Databinding. This is a light weight data binding framework for WSDL to Java conversions. This is Axis’s custom framework but is not as powerful as XML Beans.
• XMLBeans: This is the most power full xml to Java binding frame work. It provides a powerful WSDL to Java compiler.
• JiBX : This framework lets you create your own Java Objects and thus results in a clean and understandable code.

Use of WSDL contracts

In real world there can be number of groups developing various systems across various locations. Let’s assume an indicative scenario

• Service A is developed by a team in US and sends service requests to Service B and Service C
• Service B is developed in UK and sends service request to Service C
• Service C is developed in India
• Each service has on an average fifty operations

Question: Now how do we integrate all these teams easily?
Answer: The project architect creates a service contract for each service. This is usually a WSDL file. These WSDL files are sent to all project teams so that each of these project teams can work independently.

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