Simple Object Access Protocol (SOAP) is an XML-based protocol for accessing web services. It is a W3C recommendation for communication between two applications, and it is a platform- and language-independent technology in integrated distributed applications.

While XML and HTTP together make the basic platform for web services, the following are the key components of standard SOAP web services:

• SOAP: This is an XML-based protocol for accessing web services. It is also a W3C recommendation for application integration over networks. Being an XML-based implementation, SOAP is a platform- and language-independent technology. Applications developed in different languages, such as Java, PHP, or .Net, can use this technology.
• Universal Description, Discovery, and Integration (UDDI): UDDI is an XML-based framework for describing, discovering, and integrating web services. It acts as a directory of web service interfaces described in the WSDL language.
• Web Services Description Language (WSDL): WSDL is an XML document containing information about web services, such as the method name, method parameters, and how to invoke the service. WSDL is part of the UDDI registry. It acts as an interface between applications that want to interact based on web services.

The following diagram shows the interaction between the UDDI, Service Provider, and service consumer in SOAP web services:

The characteristics of SOAP web services are as follows:

• Web Service Security: SOAP web services are considered a secured web service with its security implementation termed as "WS-Security."
• Language and platform independence: SOAP web services can be developed using diverse programming languages and can be deployed on any platform. They also allow seamless integration.
• Performance: Being an XML-based protocol and carrying multiple standards in its development, SOAP web service interaction requires more network bandwidth and resource allocation compared to other web services.
• WSDL: This is the only standard mechanism to define and discover SOAP web services.

Spring Web Services (Spring-WS) is a product of the Spring community that is focused on creating document-driven web services. Spring-WS aims to facilitate contract-first SOAP service development, allowing the creation of flexible web services using one of the many ways to manipulate XML payloads. The product is based on Spring itself, which means you can use Spring concepts, such as dependency injection, as an integral part of your web service.