Ntg web services

Web Services
Farag Zakaria
ITI-JAVA 30

Agenda
• Web services concept.
• Why web services?
• When to use web services
• Web services architecture
• SOAP
• WSDL
• JAX-WS
• JAX-WS vs. JAX-RPC
• RESTful web services

Web services concept
• Web service is a software system identified by a
URI whose public interfaces and bindings are
defined ,described and discovered by XML
artifacts.(W3C)
• Client server application
• Application to application communication
• Interoperability (standard communication)
• Neutral (platform & language independent).

Why web services
• Interoperability (SOAP messaging).
• Economical (recycled components, no
installation and tight integration of software).
• Accessible (applications are exposed and
accessed on the web.)
• Available (services are on any device, any
where, anytime.)
• Scalable (no limit on scope of application and
their number.)

Agenda
• Web services concept.
• Why web services?
• When to use web services?
• Web services architecture
• SOAP
• WSDL
• JAX-WS
• JAX-WS vs. JAX-RPC

When to use web services ?
• Applications do not have severe restrictions on
reliability and speed.
• Cooperation among different application.
• Upgrading services independently from clients
without changing the WSDL.
• Services can be easily expressed with simple
request/response semantics and simple state
•

SOAP(Simple Object Access Protocol)
• Define communication format between client
and web service(XML message format).
• Wire protocol extension for conveying RPC calls.
• SOAP is not a transport protocol. You must
attach your message to a transport mechanism
like HTTP.

SOAP structure
• A SOAP message is contained in an envelop.
• The envelop element in turn contain (in order)
1. An optional header with one or more child
entries. (security , transaction)
2. A body element that can contain one or more
child entries. These child entries may contain
arbitrary XML data.(application data)
• Header entries may optionally have a
“mustUnderstand” attribute.
mustUnderstand=1 recipient must process header
mustUnderstand=0 optional header
•

SOAP structure(cont.)
• The body contains the XML message that you
are transmitting.
• The message format is not specified by SOAP.
The <Body></Body> tag pairs are just a way to notify
the recipient that the actual XML message is contained
therein.
The recipient decides what to do with the message.

WSDL(Web Service Description
Language)
• Defines what your service does and how it is
invoked.
• Guideline for constructing SOAP message.
• XML language for writing APIs(generating
client code to use the web service).
• Verbose

WSDL documents parts
• Data definition (in XML) for custom types.
• Abstract message definitions (request, response)
• Organization of messages into “ports” and
“operations” (classes and methods).
• Protocol bindings (to SOAP, for example)
• Service point locations (URLs)

WSDL document parts(Data Definition)

JAX-WS
• Simpler way to develop/deploy web services
- POJO + Annotation.
- No deployment descriptor is needed.
- Layered programming model
• Layered programming model
- Server side
- Client side
- Business layer

Programming model(server side)
• Write a POJO implementing the service
• Add @WebService annotation to it
• Deploy the application
• Point your clients at the WSDL
http://mysite/myapp/service.wsdl

Example(Server side)
@WebService(name="AddNumbers",
portName="CalculatorPort",
serviceName="CalculatorService")
public class NumbersWebService
{
@WebMethod(operationName="add")
@WebResult(name="result")
public int add(@WebParam(name="first") int first,
@WebParam(name="second") int second)
{
return first + second;
}
}

Programming model(client side)
• You need to know the url of WSDL
• Generate service classes and interfaces.
• Create object from service class
• Get a proxy using a get<ServiceName>Port
method.
• Invoke any remote operations.

Example(Client side)
• CalculatorService service = new
CalculatorServiceLocator();

AddNumbers calc = service.getCalculatorPort();

System.out.println(calc.add(3, 4));

JAX-WS vs. JAX-RPC
JAX-WS JAX-RPC
Map to JAVA 1.5 and higher Map to JAVA 1.4
Support SOAP 1.1 and SOAP 1.2 Support SOAP 1.1
Data mapping model (JAXB) Has its own data mapping model
Support MTOM through (JAXB)
Asynchronous communication

Agenda
• REST Architecture principales
• RESTful web services & WADL.
• REST vs. Traditional web services
• RESTful advantages

REST Architecture principales
• Representational State Transfer.
• Every thing is a resource.
• Resources are addressable.
• Resources have an interface(operations and data
types).
• Protocol is client-server, stateless, cacheable,
layered.

RESTful web services & WADL.
• REST applied to web services.
- web service accessible through URI.
- operations are HTTP primitives(PUT,GET,..).
- Web services returns a MIME type(XML,
JSON, …).
• More resource efficient than SOAP
- java class + annotations (for URI, operations,
Data types).

RESTful web services & WADL.(cont.)
• Annotations
- @Path(“”) for URI of service.
- @GET,@POST,.. for Http methods.
- @Produces(“…”) to define format of
returned data
- @Consumes (“…”) to define format of
accepted input data

<servlet>
<servlet-name>ServletAdaptor</servlet-name>
<servlet-class>
com.sun.jersey.spi.container.servlet.ServletContainer
</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>ServletAdaptor</servlet-name>
<url-pattern>/resources/*</url-pattern>
</servlet-mapping>

@Path("/hello")

@Consumes("text/html")

public class RESTWSTest
{
@GET
@Produces("text/html")
public String sayHello(@QueryParam("name") String name)
{
return "<html><body><h1>Hello " + name +
"</h1></body></html>";
}

}

• WADL web application description language.
- easy to understand.
- HTTP assumed.
• XML-based language.
• Development language + platform neutral.
• Aligned with REST terminology.
• WADL elements
- resources
- methods
- representations

WADL
<application>
<doc jersey:generatedBy="Jersey: 1.1.4 11/10/2009 05:36 PM"/>
<resources base="http://localhost:8080/WebServicesREST/resources/">
<resource path="/hello">
<method id="sayHello" name="GET">
<request>
<param name="name" style="query" type="xs:string"/>
</request>
<response>
<representation mediaType="text/html"/>
</response>
</method>
</resource>
</resources>
</application>

Agenda
• REST Architecture principales.
• RESTful web services & WADL.
• REST vs. Traditional web services
• RESTful advantages

REST vs. Traditional web services
• Traditional web services
- a lot of custom methods(ports according to
business).
- use http to transport soap
• RESTful
- fixed methods(Http methods).
- Http is the protocol.

RESTful advantages
• More secure over http (use web port 80)
• Ease of testing (only browser needed).
• Thin client.
• Save memory.(no need to build xml tree in memory).

If time allowed
• SOAP Handler Demo

References
• JavaPassion web site
• Sun Java JEE6 tutorial
• Sun Java Web Services tutorial

Ntg web services

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