Web Services- SOAP,WSDL,UDDI with EBook

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Web Services- SOAP,WSDL,UDDI with EBook

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Web Services- SOAP,WSDL,UDDI with EBook

Web services can convert your applications into web-applications.web servicesare published, found, and used through the web. By using web services, your application can publish its function or message to the rest of the world.web services use xml to code and to decode data, and soap to transport it using open protocols.

Web services are application components
Web services communicate using open protocols
Web services are self-contained and self-describing
Web services can be discovered using UDDI
Web services can be used by other applications
XML is the basis for Web services
Basic Web services platform is XML + HTTP

Web services platform elements includes:

SOAP (Simple Object Access Protocol)
UDDI (Universal Description, Discovery and Integration)
WSDL (Web Services Description Language)

What is SOAP?

SOAP is an XML-based protocol to let applications exchange information over HTTP.

Or more simple: SOAP is a protocol for accessing a Web Service.

SOAP stands for Simple Object Access Protocol
SOAP is a communication protocol
SOAP is a format for sending messages
SOAP is designed to communicate via Internet
SOAP is platform independent
SOAP is language independent
SOAP is based on XML
SOAP is simple and extensible
SOAP allows you to get around firewalls
SOAP is a W3C standard

Here are some important syntax rules:

A SOAP message MUST be encoded using XML
A SOAP message MUST use the SOAP Envelope namespace
A SOAP message MUST use the SOAP Encoding namespace
A SOAP message must NOT contain a DTD reference
A SOAP message must NOT contain XML Processing Instructions

What is WSDL?

WSDL is an XML-based language for locating and describing Web services.

WSDL stands for Web Services Description Language
WSDL is based on XML
WSDL is used to describe Web services
WSDL is used to locate Web services
WSDL is a W3C standard

What is UDDI?

UDDI is a directory service where companies can register and search for Web services.

UDDI stands for Universal Description, Discovery and Integration
UDDI is a directory for storing information about web services
UDDI is a directory of web service interfaces described by WSDL
UDDI communicates via SOAP
UDDI is built into the Microsoft .NET platform

SOAP Building Blocks

A SOAP message is an ordinary XML document containing the followingelements:

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

Skeleton SOAP Message

<?xml version=”1.0″?>
<soap:Envelope
xmlns:soap=”http://www.w3.org/2001/12/soap-envelope”
soap:encodingStyle=”http://www.w3.org/2001/12/soap-encoding”><soap:Header>
…
</soap:Header><soap:Body>
…
<soap:Fault>
…
</soap:Fault>
</soap:Body></soap:Envelope>

The SOAP Envelope Element

The required SOAP Envelope element is the root element of a SOAP message. This element defines the XML document as a SOAP message.

Example

<?xml version=”1.0″?>
<soap:Envelope
xmlns:soap=”http://www.w3.org/2001/12/soap-envelope”
soap:encodingStyle=”http://www.w3.org/2001/12/soap-encoding”>
…
Message information goes here
…
</soap:Envelope>

The xmlns:soap Namespace

Notice the xmlns:soap namespace in the example above. It should always have the value of: “http://www.w3.org/2001/12/soap-envelope”.If a different namespace is used, the application generates an error and discards the message.

The encodingStyle Attribute

The encodingStyle attribute is used to define the data types used in the document. This attribute may appear on any SOAP element, and applies to the element’s contents and all child elements.

Syntax

soap:encodingStyle=”URI“

Example

The SOAP Header element contains header information.

The SOAP Header Element

The optional SOAP Header element contains application-specific information (like authentication, payment, etc) about the SOAP message.

If the Header element is present, it must be the first child element of theEnvelope element.

<?xml version=”1.0″?>
<soap:Envelope
xmlns:soap=”http://www.w3.org/2001/12/soap-envelope”
soap:encodingStyle=”http://www.w3.org/2001/12/soap-encoding”><soap:Header>
<m:Trans xmlns:m=”http://www.javamazon.com/transaction/”
soap:mustUnderstand=”1″>234
</m:Trans>
</soap:Header>
…
…
</soap:Envelope>

The example above contains a header with a “Trans” element, a “mustUnderstand” attribute with a value of 1, and a value of 234.

The attributes defined in the SOAP Header defines how a recipient should process the SOAP message.

The mustUnderstand Attribute

The SOAP mustUnderstand attribute can be used to indicate whether a header entry is mandatory or optional for the recipient to process.

If you add mustUnderstand=”1″ to a child element of the Header element it indicates that the receiver processing the Header must recognize the element. If the receiver does not recognize the element it will fail when processing the Header.

Syntax

soap:mustUnderstand=”0|1″

Example

<?xml version=”1.0″?>
<soap:Envelope
xmlns:soap=”http://www.w3.org/2001/12/soap-envelope”
soap:encodingStyle=”http://www.w3.org/2001/12/soap-encoding”><soap:Header>
<m:Trans xmlns:m=”http://www.javamazon.com/transaction/”
soap:mustUnderstand=”1″>234
</m:Trans>
</soap:Header>
…
…
</soap:Envelope>

The actor Attribute

A SOAP message may travel from a sender to a receiver by passing different endpoints along the message path. However, not all parts of a SOAP message may be intended for the ultimate endpoint, instead, it may be intended for one or more of the endpoints on the message path.

The SOAP actor attribute is used to address the Header element to a specific endpoint.

Syntax

soap:actor=”URI“

Example

<?xml version=”1.0″?>
<soap:Envelope
xmlns:soap=”http://www.w3.org/2001/12/soap-envelope”
soap:encodingStyle=”http://www.w3.org/2001/12/soap-encoding”><soap:Header>
<m:Trans xmlns:m=”http://www.javamazon.com/transaction/”
soap:actor=”http://www.javamazon.com/appml/”>234
</m:Trans>
</soap:Header>
…
…
</soap:Envelope>

The encodingStyle Attribute

The encodingStyle attribute is used to define the data types used in the document. This attribute may appear on any SOAP element, and it will apply to that element’s contents and all child elements.

A SOAP message has no default encoding.

Syntax

soap:encodingStyle=”URI“

The SOAP Body Element

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

Immediate child elements of the SOAP Body element may be namespace-qualified.

Example

<?xml version=”1.0″?>
<soap:Envelope
xmlns:soap=”http://www.w3.org/2001/12/soap-envelope”
soap:encodingStyle=”http://www.w3.org/2001/12/soap-encoding”><soap:Body>
<m:GetBooks xmlns:m=”http://www.javamazon.com/prices”>
<m:Item>ANDROID</m:Item>
</m:GetBooks>
</soap:Body></soap:Envelope>

The example above requests the price of apples. Note that the m:GetPrice and the Item elements above are application-specific elements. They are not a part of the SOAP namespace.

A SOAP response could look something like this:

<?xml version=”1.0″?>
<soap:Envelope
xmlns:soap=”http://www.w3.org/2001/12/soap-envelope”
soap:encodingStyle=”http://www.w3.org/2001/12/soap-encoding”><soap:Body>
<m:GetBooksResponse xmlns:m=”http://www.javamazon.com/prices”>
<m:Price>39.0</m:Price>
</m:GetBooksResponse>
</soap:Body></soap:Envelope>

The SOAP Fault Element

The optional SOAP Fault element is used to indicate error messages.

If a Fault element is present, it must appear as a child element of the Body element. A Fault element can only appear once in a SOAP message.

The SOAP Fault element has the following sub elements:

Sub Element	Description
<faultcode>	A code for identifying the fault
<faultstring>	A human readable explanation of the fault
<faultactor>	Information about who caused the fault to happen
<detail>	Holds application specific error information related to the Body element

SOAP Fault Codes

The faultcode values defined below must be used in the faultcode element when describing faults:

Error	Description
VersionMismatch	Found an invalid namespace for the SOAP Envelopeelement
MustUnderstand	An immediate child element of the Header element, with the mustUnderstand attribute set to “1″, was not understood
Client	The message was incorrectly formed or contained incorrect information
Server	There was a problem with the server so the message could not proceed

A SOAP Example

In the example below, a GetStockPrice request is sent to a server. The request has a StockName parameter, and a Price parameter 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: nnn<?xml version=”1.0″?>
<soap:Envelope
xmlns:soap=”http://www.w3.org/2001/12/soap-envelope”
soap:encodingStyle=”http://www.w3.org/2001/12/soap-encoding”><soap:Body xmlns:m=”http://www.example.org/stock”>
<m:GetText>
<m:RText>SMS</m:RText>
</m:GetText>
</soap:Body></soap:Envelope>

The SOAP response:

HTTP/1.1 200 OK
Content-Type: application/soap+xml; charset=utf-8
Content-Length: nnn<?xml version=”1.0″?>
<soap:Envelope
xmlns:soap=”http://www.w3.org/2001/12/soap-envelope”
soap:encodingStyle=”http://www.w3.org/2001/12/soap-encoding”><soap:Body xmlns:m=”http://www.example.org/stock”>
<m:GetTextResponse>
<m:RText>Honey</m:RText>
</m:GetTextResponse>
</soap:Body></soap:Envelope>

Below is the Video Tutorial on how to create a Web Service

CODE EXCEPTIONS