Tutorial on Web Services

HY559 Infrastructure Technologies for Large- Scale Service-Oriented Systems

Jason Polakis [email protected] Required Software

•Eclipse IDE for Java developers EE http://www.eclipse.org/downloads/ •Netbeans IDE http://netbeans.org/downloads/ •Apache Tomcat http://tomcat.apache.org/ •Apache AXIS2 http://axis.apache.org/axis2/java/core/download.cgi •Apache JUDDI http://juddi.apache.org/releases.html Getting Software

• Either directly from given links, or: • In Ubuntu (as root) • To search for software – apt -cache search – Returns list of with short description • To install software – apt-get install – Installs software, as well as dependencies Web Services “Any piece of software that makes itself available over the Internet and uses a standardized XML messaging system” •Extremely available •Language and platform independent •Distributed application components •Discoverable via a simple find mechanism •Components of Web Services – SOAP (Simple Object Access Protocol) – WSDL (Web Services Description Language) – UDDI (Universal Description, Discovery and Integration) Architecture

•Web Service Protocol Stack –Service transport (transport messages between applications) •HTTP, SMTP, FTP –XML messaging (encode messages in common XML format ) • XML-RPC, WS-Addressing, and SOAP –Service description (describe public interface of service) –Service discovery (centralize services into common registry) •Programming models: –REST-based web services –SOAP-based web services SOAP-based Services

•Use SOAP –protocol for exchanging structured information •Use WSDL –xml-based language for describing Web services •WSDL file –created based on the JAVA code in the service –exposed on the net •To use service, must create a client –based on WSDL info •Messages exchanged in SOAP

•Java API for XML Web Services (JAX-WS) model also used for SOAP services. Can use instead of AXIS2. WSDL example

•Web service •Single publicly available function sayHello –argument: string –return value: string WSDL Definitions element

......

•container of all other elements •specifies that this document is the HelloService •Namespace: abstract container providing context -> logical grouping of code •specifies a targetNamespace attribute (XML convention) → enables self reference •specifies a default namespace •specifies numerous namespaces that will be used WSDL types

•Describes data types used between client and server •Uses W3C XML Schema specification as default choice to define data types •If the service uses only XML Schema built-in simple types, such as strings and integers, then types element is not required WSDL message

•: describes the data exchanged between service providers and consumers •Each Web Service has two messages: input and output •Input: parameters for the Web Service •Output: return data from the Web Service •Each message contains zero or more parameters, one for each parameter of the function •Each parameter associates with a concrete type defined in the container element WSDL portType element

•Basically, defines an interface: how unrelated objects communicate with each other •"portType“ used to define one or multiple operations •Operation: a sequence of messages to form an input-output pattern •WSDL supports four basic patterns of operation –One-way (input) –Request-response (input, output) –Solicit-response (output, input) –Notification (output) •Is an abstract definition WSDL Binding Element

•Concrete implement. of •How portType operation will be transmitted •Where service is located •type attribute points to the port for the binding Binding: format of messages, soapAction HTTP header identifies the service •Body: specify the details of the input and output messages WSDL port

WSDL File for HelloService

• element defines individual endpoint. Specifies single address for binding •name attribute: unique name among all ports defined •binding attribute: refers to binding element WSDL service WSDL File for HelloService

•Defines ports supported by Web service •Service element: a collection of ports •For each supported protocol, there is one port element •clients learn from service element –where to access the service –through which port to access the Web service •Human-readable documentation •Binding attribute associates service with binding element

•Open source servlet container •HTTP web server environment for serving Java Implements •Java Servlet: class for responding to HTTP requests –Create object that receives a request –Generates responses based on requests •JavaServer Pages (JSP): serve dynamically generated web pages –Java code interleaved with static web content –Compiled and executed on server –Resulting HTML or XML document served Apache AXIS2

• Web service framework • Will run over Tomcat • SOAP / WSDL engine • Also supports RESTful web services • Web service creation example – http://netbeans.org/kb/docs/websvc/gs- axis.html#deploy_axis – http://today.java.net/pub/a/today/2006/12/13/in voking-web-services-using-apache-axis2.html Apache AXIS2

• Send SOAP messages • Receive and process SOAP messages • Create a Web service out of a plain Java class • Create implementation classes for both the server and client using WSDL • Easily retrieve the WSDL for a service • Send and receive SOAP messages with attachments • Create or utilize a REST-based Web service Netbeans IDE

•Creating an Axis2 “Hello World” Web Service •First setup Axis2 and Tomcat –http://netbeans.org/kb/docs/websvc/gs- axis.html#setup –http://netbeans.org/kb/docs/websvc/gs- axis.html#axis_options_tomcat Netbeans IDE example File -> New Project Name it AxisHello, click Finish Right-click project node , context menu opens choose New -> Other, Wizard opens Netbeans IDE example

• Click Next, Name the Java class HelloAxisWorld. • Name the package axishello. Click Finish. • Application created. Netbeans IDE example Netbeans IDE example • Time to deploy Axis2 web service to the server • Right-click the web service's node -> Deploy to Server • Axis2 AAR file created, copied to .war file used by server • To test service, expand web service node • Right-click “hello: String” node. -> Test in Browser Netbeans IDE example

• Browser opens, with test value for variables Netbeans IDE example

• Change value and press Enter. Results change. Netbeans IDE example

• Change Web Service Operation. • Edit Java file in Editor.

• Save the Java file, Redeploy Web Service and test!!! Apache JUDDI

•XML-based registry for registering and locating web service applications •Interact through SOAP, access WSDL documents Link1 , link2 , link3