Web services provide a standard way of interoperating between different applications (heterogeneous), running on different platforms, and it provides the integration of web based application using the XML, SOAP, WSDL and UDDI
XML is used to tag the data, SOAP is used to transfer the data, WSDL is used for describing the services available and UDDI is used for listing what services are available.
The Web Services Description Language (WSDL) forms the basis for Web Services. The following figure illustrates the use of WSDL. At the left is a service provider. At the right is a service consumer. The steps involved in providing and consuming a service are:
- A service provider describes its service using WSDL. This definition is published to a directory of services. The directory could use Universal Description, Discovery, and Integration (UDDI). Other forms of directories can also be used.
- A service consumer issues one or more queries to the directory to locate a service and determine how to communicate with that service.
- Part of the WSDL provided by the service provider is passed to the service consumer. This tells the service consumer what the requests and responses are for the service provider.
- The service consumer uses the WSDL to send a request to the service provider.
- The service provider provides the expected response to the service consumer.
Ok Lets talks about WSDL !
definitions
The definitions element is the root element of all WSDL. It defines the name of the web service and also declares multiple namespaces.
types
The type’s element describes all the data types used between the client and server. To define complex data type will be using XSD
<xs:element name="helloUser">
<xs:complexType>
<xs:sequence>
<xs:element name="name" type="xs:string"/>
</xs:sequence>
</xs:complexType>
</xs:element>
This describes the parameter (input/output)and its types being exchanged between the Web service client and server.
<s0:message name="helloUser">
<s0:part element="s1:helloUser" name="parameters"/>
</s0:message>
portType
This element defines operation (method name) with input and output parameter.
<s0:portType name="Hello">
<s0:operation name="helloUser" parameterOrder="parameters">
<s0:input message="s1:helloUser"/>
<s0:output message="s1:helloUserResponse"/>
</s0:operation>
</s0:portType>
binding
This element includes supported operations, as well as the input and output for each operation. The bindings provide concrete information on what protocol is being used, how the data is being transported, and where the service is located
<s0:binding name="HelloServiceSoapBinding" type="s1:Hello">
<s2:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/>
<s0:operation name="helloUser">
<s2:operation soapAction="" style="document"/>
<s0:input>
<s2:body parts="parameters" use="literal"/>
</s0:input>
<s0:output>
<s2:body parts="parameters" use="literal"/>
</s0:output>
</s0:operation>
</s0:binding>
<s0:service name="HelloService">
<s0:port binding="s1:HelloServiceSoapBinding" name="HelloSoapPort">
<s2:address location="http://localhost:7001/Hello/Hello"/>
</s0:port>
</s0:service>
How to create a simple webservice application?
The following things are required to run this application
1) Weblogic10.3/x
http://www.oracle.com/technology/software/products/ias/htdocs/wls_main.html
2) Ant 1.6.5 or latest
http://ant.apache.org/bindownload.cgi
3) Jdk.15 or above
http://java.sun.com/javase/downloads/index.jsp
The following example shows how to create a Web Service called HelloWorld that includes two operations, helloByDefault and helloByUserName.
package com.javatch;
import javax.jws.WebService;
@WebService(name="HelloSoapPort", serviceName="HelloService")
public class HelloWorld{
// By default, all public methods are exposed as Web Services operation, else you can use @WebMethod()
public String helloByDefault(){
String saySomething = "Hello, Welcome come to Webservice world";
System.out.println(saySomething);
return saySomething;
}
public String helloByUserName(String name){
return "Hello "+name + "Welcome come to javatch" ;
}
}
Now we are ready with our service, next step is to generate WSDL. Umm..How?
We have create ant script to generate our service using jwsc task (for weblogic 10x)
Create a build.xml file and copy the following in to that
<project default="all">
<target name="all" depends="clean, build"/>
<target name="clean">
<delete dir="output"/>
</target>
<taskdef name="jwsc" classname="weblogic.wsee.tools.anttasks.JwscTask"/>
<target name="build">
<jwsc
srcdir="com"
destdir="output">
<jws file="Hello.java"/>
</jwsc>
</target>
</project>
J We are ready with our service and ant script lets create the WSDL file
Note: set ANT_HOME - should point to the ant extract directory ex- c:\ apache-ant-1.6.5
Add this line in the path - %ANT_HOME%\bin
Open a command prompt and navigate to web logic directory (C:\bea10\wlserver_10.3\server\bin) and execute “setWLSEnv.sh”
รจ Then go to directory were we have our build.xml and execute it. (just type ant press enter)
Create Client.java, before we do this, we need to create client stub. This is done by the following ant script
<project default="jar">
<path id="client-path">
<pathelement path="src"/>
</path>
<taskdef name="clientgen"
classname="weblogic.wsee.tools.anttasks.ClientGenTask"/>
<target name="build">
<clientgen
wsdl="http://192.168.1.2:7001/HelloWorld/HelloWorld?WSDL"
destdir="output"
packageName="com.javatch"/>
<javac
srcdir="output"
destdir="output"
includes="**/*.java"/>
</target>
<target name="jar" depends ="build">
<jar jarfile="client.jar" >
<fileset dir="output" />
</jar>
</target>
</project>
public class Client{
public static void main(String args[])
throws Exception{
String wsdl="http://192.168.1.2:7001/HelloWorld/HelloWorld?WSDL";
HelloService service = new HelloService_Impl(wsdl);
HelloSoapPort h=service.getHelloSoapPortSoapPort();
String name="My Friend";
String msg=h.helloByUserName(name);
System.out.println("The server message : "+msg);
}
}
Here you go with simple webservice application :-)
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