SOAP(Simple Object Access Protocol)

SOAP:

SOAP is an acronym for Simple Object Access Protocol. SOAP defines a protocol for message exchange between applications. SOAP provides a way to communicate between applications running on different operating systems, with different technologies and programming languages.

SOAP describes envelope and message formats, and has a basic request/response SOAP is a communication protocol

SOAP is for communication between applications SOAP is a format for sending messages

SOAP communicates via Internet SOAP is platform independent

SOAP is language independent SOAP is based on XML

SOAP is simple and extensible

SOAP is a W3C recommendation SOAP Building Blocks

A SOAP message is an ordinary XML document containing the following elements:

An Envelope element that identifies the XML document as a SOAP message A Header element that contains header information

A Body element that contains call and response information A Fault element containing errors and status information

 Structure of SOAP Message

The following code fragment gives an outline of the SOAP message // code for HTTP binding

HTTP binding

// used to directs the message

Envelop

//  helps the server to identify the message as SOAP

Header

//  Optional. It adds features to SOAP message such as authentication, message route etc.

Body

// contain actual message

<soap:Envelope xmlns:soap="uri" soap:encodingStyle="uri">

<soap:Header>

... ... ...

</soap:Header>

<soap:Body>

... ... ...

<soap:Fault>

... ... ...

</soap:Fault>

</soap:Body>

</soap:Envelope>

The SOAP Envelope element is the root element of a SOAP message. This element defines the XML document as a SOAP message. The xmlns:soap namespace defines the Envelope as a SOAP Envelope. The encodingStyle attribute is used to define the data types used in the document.

The SOAP Header element contains header information. If the Header element is present, it must be the first child element of the Envelope element.

The SOAP Body element contains the actual SOAP message intended for the ultimate endpoint of the message.

The SOAP Fault element holds errors and status information for a SOAP message.

A SOAP Example

In the example below, a GetStockPrice request is sent to a server. The request has

a StockName and Price parameters that will be returned in the response. The namespace for the function is defined in "http://www.example.org/stock".

A SOAP request:

POST /InStock HTTP/1.1 Host: www.example.org

Content-Type: application/soap+xml; charset=utf-8 Content-Length: n bytes

<?xml version="1.0"?>

<soap:Envelope xmlns:soap="uri" soap:encodingStyle="uri"> <soap:Body xmlns:m="http://www.example.org/stock"> <m:GetStockPrice>

<m:StockName>IBM</m:StockName>

</m:GetStockPrice>

</soap:Body>

</soap:Envelope>

The SOAP response:

HTTP/1.1 200 OK

Content-Type: application/soap+xml; charset=utf-8 Content-Length: n bytes

<?xml version="1.0"?>

<soap:Envelope xmlns:soap="uri" soap:encodingStyle="uri"> <soap:Body xmlns:m="http://www.example.org/stock"> <m:GetStockPriceResponse>

<m:Price>34.5</m:Price>

</m:GetStockPriceResponse>

</soap:Body>

</soap:Envelope>

SOAP and HTTP

A SOAP method is an HTTP request/response that complies with the SOAP encoding rules. SOAP message is HTTP + XML = SOAP.

A SOAP request could be an HTTP POST or an HTTP GET request.

Java support for SOAP

Java provides support for creating and manipulating SOAP documents through SAAJ which is an acronym of Soap with Attachments Api for Java. This API is part of JWSDP. Related technologies

The alternative for creating web services using JSWDP is sun J2EE platform, Apache

Axis.

Also, IBM, WebSphere, BEA and WebLogic development platforms are alternative tools for developing java based web services.

Personal Home Page (PHP) development platform can also be used for creating web services. It contains PEAR (Personal home page Extension and Application Repository) for parsing a WSDL document.

UDDI (Universal Discovery Description and Integration) is used to register and locate web services. Alternative to UDDI is JAXR (Java Api for Xml Registry)

WS-I Basic Profile (Web Service Interoperability Basic Profile) is a tool which helps the developers how to use various web service technologies.