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There are two main types of web-services: REST (REpresentational State Transfer) and WSDL (Web Services Description Language) /SOAP.

REST services

REST services use the HTTP protocol. As described on wikipedia, a common mapping of services is:

Resource

GET

PUT

POST

DELETE

Collection URI, such as http://example.com/resources/

List the URIs and perhaps other details of the collection's members.

Replace the entire collection with another collection.

Create a new entry in the collection. The new entry's URL is assigned automatically and is usually returned by the operation.

Delete the entire collection.

Element URI, such as http://example.com/resources/item17

Retrieve a representation of the addressed member of the collection, expressed in an appropriate Internet media type.

Replace the addressed member of the collection, or if it doesn't exist, create it.

Treat the addressed member as a collection in its own right and create a new entry in it.

Delete the addressed member of the collection.

Tools to build REST services

The Java API for XML Web Services (JAX-WS) provides full support for building and deploying REST Web services. It is tightly integrated with the Java Architecture for XML Binding (JAXB) for binding XML to Java data and is included in Java 6.

Some guidelines on building REST Web services can be found online.

WSDL/SOAP Web services

Web Service Description Language (WSDL) Web services operate by exchanging Simple Object Access Protocol (SOAP) messages with clients over HTTP.

WSDL Web services are defined by their WSDL document, an XML format that represents an interface to a Web service. WSDL is machine-readable description of the operations (functions) and parameters offered by the service, i.e. XML message types that the service receives and produces and that get wrapped in SOAP messages exchanged between the client and the service.

WSDL binding describes how a particular Web service is bound to the underlying SOAP messaging protocol (or any other protocol used as a carrier). A WSDL-SOAP binding can be either a Remote Procedure Call (RPC)-style binding or a document-style binding. A SOAP binding can also have an encoded use or a literal use. This gives four style/use models:

  • RPC/encoded
  • RPC/literal
  • Document/encoded
  • Document/literal

There is also a fifth binding style that is commonly referred to as the document/literal wrapped. Thus, developers have five binding styles to choose from when creating a WSDL file. A good description of the differences between these styles can be found online.

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