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Java Web Service
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Objective
What Is a Web Service? Identifying Web Service Standards
JEE Web Service APIs
Using Java API for XML based-WS API (JAX-WS) Developing a Web Service by Using the Bottom-
Up Approach
Invoking the Web Service with a Java Client
Application
Developing a Web Service by Using the Top-
Down Approach
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What is Service ?
A service is a behavior that is provided by a
component for use by any other component
based only on the interface contract.
A service has a network-addressable interface.
A service may be dynamically discovered and
used.
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Service-oriented Architecture
SOA is a design and a way of thinking about building s/w components.
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Benefits of SOA
Better reuse
Build new client functionality on top of existing
Business Services
Well defined interfaces
Make changes without affecting clients
Easier to maintain
Changes/Versions are not all-or-nothing
Better flexibility
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What is aWeb Service?
In simpler terms
Software that performs a task.
Sits on a network so other systems can talk toit (most often SOAP over HTTP).
Has a defined, published interface (viaWSDL).
Is pla
tforma
nd la
ngua
ge independent. Typically uses XML.
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Web service standards
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Web services programming stack.
Web service stack is a collection of
standardized protocols and application
programming interfaces (APIs) that lets
individuals and applications locate and utilize
Web services.
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Simple Object Access Protocol
SOAP is a lightweight protocol for exchange of information in a
decentralized, distributed environment.
It is an XML based protocol that consists of three parts:
1. SOAP envelope that defines a framework for describing what is in amessage
and how to process it.
2. SOAP encoding rules for expressing instances ofapplication-defined data types.
3. SOAP for representing remote procedure calls and responses.
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SOAP Envelope the primary container
root element of the message using the XML namespace
http://schemas.xmlsoap.org/soap/envelope/ (As per SOAP 1.1spec.)
SOAP Header first immediate child element of a SOAP envelope
zero or more optional child elements mustUnderstand attribute
represents a transaction semantics entry
provide mechanisms to extend
defining high-level functionalities such as security, transactions,priority, and auditing
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SOAP Header
The Header element is encoded as the first immediate child element of the
SOAP Envelope XML element. All immedia
te ch
ild elements of th
e Hea
derelement are called header entries.
The encoding rules for header entries are as follows:
1. A header entry is identified by its fully qualified element name, which
consists of the namespace URI and the local name.
2. The SOAP encodingStyle attribute MAY be used to indicate the encoding style
used for the header entries.
3. The SOAP mustUnderstand attribute.
5
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SOAP Body SOAP envelopes child element
one or more optional SOAP body block entries
mandatory processing information or the payload intended for thereceiver
Body block can contain RPC method and its parameters
Target application (receiver) specific data
SOAP fault for reporting errors and status information
SOAP Fault error and/or status information
elements to define the error and status Faultcode (VersionMismatch, MustUnderstand, Client, Server)
Faultstring, Faultactor, Detail
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SOAP mustUnderstand the processing of a SOAP header block is mandatory
or optional at the target SOAP node
SOAP Attachments
An XML format and any data format (can be ASCII orbinary)
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Examples of SOAP Messages
SOAP Message Embedded in HTTP Request
POST /StockQuote HTTP/1.1
Host: www.stockquoteserver.com
Content-Type: text/xml; charset="utf-8"
Content-Length: nnnn
SOAPAction: "Some-URI"
L&T
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SOAP Message Embedded in HTTP Response
HTTP/1.1 200 OKContent-Type: text/xml; charset="utf-8"Content-Length: nnnn
34.5
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SOAP Communication
SOAP RPC remote procedural call-based synchronous
communication tightly coupled communication model based on
requests and responses.
SOAP Messaging
document-driven communication Using synchronous and asynchronous messaging
loosely coupled communication model based onmessage notification and the exchange of XMLdocuments
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Web service Description Language -WSDL
Interface Definition Language (IDL) service based on XML that
defines the service interface and its implementation characteristics.WSDL document contains following (W3C spec):
Types a container for data type definitions using some type system
(suchas XSD).
Message an abstract, typed definition of the data being communicated.
Oper
ation
ana
bstra
ct description ofa
na
ction supported by th
eservice.
Port Typean abstract set of operations supported by one or more
endpoints.
Binding a concrete protocol and data format specification for a
particular port type.
Port a single endpoint defined as a combination ofa binding and anetwork address.
Service a collection of related endpoints.
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The main structure of a WSDL document :
definition of types........
definition ofamessage....
definition ofa port.......
definition ofa binding....
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WSDL Ports
The element is the most importantWSDL element.
It describes a web service, the operations that can be performed, and the
messages that are involved.
WSDL Messages
The element defines the data elements ofan operation.
Eachmessage can consist of one or more parts. The parts can be compared
to the parameters ofa function call in a traditional programming language.
WSDL Types
The element defines the data types that are used by the web
service.
For maximum platform neutrality, WSDL uses XML Schema syntax to define
data types.
WSDL Bindings
The element defines the message format and protocol details for
each port.
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UDDI
The Universal Description, Discovery, and Integration (UDDI) specifications
define how to publishand discover information about services in a UDDI-conforming registry.
The UDDI schema identifies the types of XML data structures that comprise an
entry in the registry for a service.
UDDI registry as a "Yellow Pages" for web services.
Web services uses UDDI for discovery and lookup services.
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WSDL
Web Service(J2EE, PL/SQL,
.NET,C/C++,
Legacy )
Web Service(J2EE, PL/SQL,
.NET,C/C++,
Legacy )
Web ServiceClient
(J2EE, .NET,
PL/SQL )
Web ServiceClient
(J2EE, .NET,
PL/SQL )
Points to
description
Describes
Service
Finds
Service
Invokes with
XML Messages
BasicWeb Services
SOAP
UDDI
Registry
Points toservice
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