Exercise SBPM Session-4 : Web Services

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1 Arbeitsgruppe Exercise SBPM Session-4 : Web Services Kia Teymourian Corporate Semantic Web (AG-CSW) Institute for Computer Science, Freie Universität Berlin kia@inf.fu-berlin.de

2 Agenda Presentation of last Exercise (BPMN) Web Services Web Service Example Details about Apache Axis2 Description of next exercise sheet (Web Services)

3 Web Services and BPEL Why Web Services? Business Process Execution Language (BPEL), or Web Services Business Process Execution Language (WS-BPEL) BPEL is a Web Service orchestration language BPEL provides us with means for modeling the control flow of our application The actual functionality is provided by Web Services.

4 Definition of Web Services? A Web service is a software system identified by a URI, whose public interfaces and bindings are defined and described using XML. Its definition can be discovered by other software systems. These systems may then interact with the Web service in a manner prescribed by its definition, using XML based messages conveyed by Internet protocols. [W3C]

5 What are Web Services? Identifiable by URIs Interfaces are defined in XML Web Services could be discovered by other systems Interaction over XML-Based transmitted by Internet protocols. XML Application 1 Application 2

6 Benefits of Web Services Interoperability in a heterogeneous environment Makes loosely coupling between systems possible Platform independent from the communicating systems Business services through the Web Provide wide usage of services, because there is no platform specific requirements Integration with existing systems Decreases the integration costs and shorts the integration processes Freedom of choice Programming productivity, development of application in timely fashion What are the disadvantages of Web Services? (At the Ende of exercise)

7 Web Service Components Discovery (UDDI) To find out where the web services are and which enterprises provide these Description (WSDL) Description of a web service and how can it be integrated in an application Packaging (SOAP) The encapsulating of interaction with a web service Transport (HTTP) Transport of data over the Internet

8 Web Service Usage WSDL Web Service Consumer Usage SOAP Web Service Provider

9 Web Service Description Language Description Language for the specification of web services Specifications in WSDL Which services provide which methods? Over which ports, protocols could the methods be called? Which messages are required for method call? Which names and which parameters have a message? How are the data types in a messages? Have look at

10 Simple Object Access Protocol (SOAP) Problems by the interaction with web services Content should be understandable by all partners Possibility for the interpretation should be delivered together with the data message Interpretable Meta-information should be delivered, DATA XML SOAP = Web Service call with data package in XML format SOAP provide structured data over http to the Web Services Packaging of data in an Envelope SOAP messages are text data which can be transported over http or SMTP SOAP defines: How a call of an endpoint, method name, parameters should be translated to XML? How the results should be translated to XML? In which format the data should be transported over the network?

11 SOAP Structure Http Post SOAP Envelope SOAP Head SOAP Body

12 SOAP Envelope Envelope analog to the real world postal mail envelop, a container for request and response Includes optional details about encoding style (attribute encodingstyle), could also be used for header and body. Example of an SOAP-Envelopes: <SOAP-ENV:Envelope xmlns:soap-env=" xmlns:soap-enc=" xmlns:xsi=" xmlns:xsd=" <SOAP-ENV:Header> </SOAP-ENV:Header> <SOAP-ENV:Body> </SOAP-ENV:Body> </SOAP-ENV:Envelope>

13 SOAP Header Optional SOAP Header element contains applicationspecific information SOAP defines three attributes Attributes are: mustunderstand, actor, and encodingstyle. Actor: defines the end point by message forwarding MustUnderstand: defines that a header entry is mandatory or optional for the recipient to process. Attributes defined in the SOAP Header defines how a recipient should process the SOAP message. Example: <SOAP-ENV:Header> <m:transaction xmlns:t="some-uri" SOAP-ENV:actor="other-uri" SOAP ENV:mustUnderstand= 1 > 234 </m:transaction> </SOAP-ENV:Header>

14 SOAP Body Mandatory element Qualified namespaces possible, but not required Includes the main message for the WS end point Example of a SOAP Body: <SOAP-ENV:Body> <m:dogooglesearch xmlns:m="urn:googlesearch" <keywords xsi:type="xsd:string">abcd</keywords> <maxresults xsi:type="xsd:int">10</maxresults> <filter xsi:type="xsd:boolean">1</filter> </m:dogooglesearch> </SOAP-ENV:Body>

15 Implementation WS Implementation in different programming languages, framework, Java.NET Apache Axis 1/2 Mono Python Perl PHP We use Apache Axis2 as WS Framework in this exercise

16 Apache Axis 2 Apache extensible Interaction System (Axis) IBM SOAP4J -> Apache SOAP -> Apache Axis -> Apache Axis2 Axis2 Highlights: Open source license High performance Flexible configuration, extensible through modules Improved client API (full WSDL and WS-policy support) Deployment of services and modules via archive files Hot deployment and hot update without container restart

17 Working with Apache Axis2 Axis 2 is a framework and tool collection WAR distribution for running web services Standard distribution for WS development Installation prerequisites for Axis2 Installation: JDK >= 1.5 Servlet Container (We use Apache Tomcat) Prerequisites for deployment/call of WS JDK>= 1.5 Apache Ant Apache Axis2

18 Apache Axis2 Installation Install JDK >= Install Apache Ant Frequent Problems/Errors Set JDK/JRE/Ant in you path variable Environment variable JAVA_HOME, ANT_HOME are not set Install it on your notebook, Desktop (localhost) University PC Pool, Thin client collision of ports and servers on the server side possible

19 Apache Axis2 Installation Install Apache Tomcat version 6, Core Frequent Problems/Errors Environment variable CATALINA_HOME is not set Variable should point to the root directory of the tomcat installation Check your installation Call the URL in your browser Administration menu Status

20 Apache Axis 2 Installation Install Apache Axis2 Version 1.5.4, WAR and Standard binary Install the WAR file (Web Archive) in tomcat Call the URL in browser Menu administration tomcat manager Upload Axis2 WAR (section WAR file to deploy) Check the installation Call the URL in browser Call menu point validate

21 Deployment of an Axis2 WS Example Web Service, AddNumberService Add two number and return the result Package de.fu_berlin.csw; Public class AddNumberService { Public AddNumberService() { } } Public int add(int a, int b) { return(a+b); }

22 Deployment of an Axis2 WS Web Service is defined by the file service.xml Defines which classes implement the WS Defines which methods of the classes are available/visible for WS <service name="addnumberservice"> <description>addnumberservice</description> <parameter name="serviceclass"> de.fu_berlin.csw.addnumberservice </parameter> <operation name="add"> <messagereceiver class="org.apache..." /> </operation> </service> Create a Axis2 Service Archive (AAR) with Ant script ant -f compile.xml and at the end ant

23 Deployment of an Axis2 WS Created AAR can be uploaded via Browser in Axis2 module Default User name/password: admin/axis2

24 Call a Web Service in Java Axis2 provides tools for encapsulation of WS calls WSDL2Java creates stub classes on the basis of WSDL run: wsdl2java -uri -o client -s -p de.fu_berlin.csw.client On Linux wsdl2java.sh Prerequisites: Apache Axis2 Standard Binary distribution (ver. 1.5) should be installed Directory axis /bin in path Environment variable AXIS2_HOME should be set

25 Call a Web Service in Java After installing Axis2 standard, set the CLASSPATH for: axis2-kernel jar: axis2-adb jar: axiom-api jar: axiom-api jar: axiom-api jar: XmlSchema jar: axiom-impl jar: commons-httpclient-3.1.jar: commons-codec-1.3.jar In Linux environment use this: export CLASSPATH=$CLASSPATH:$AXIS2_HOME/axis2-kernel jar: $AXIS2_HOME/axis2-adb jar:$AXIS2_HOME/axiom-api jar: $AXIS2_HOME/axiom-api jar:$AXIS2_HOME/axiom-api jar: $AXIS2_HOME/XmlSchema jar:$AXIS2_HOME/axiom-impl jar: $AXIS2_HOME/commons-httpclient-3.1.jar:$AXIS2_HOME/commonscodec-1.3.jar

26 Call a Web Service in Java package de.fu_berlin.csw.client; import de.fu_berlin.csw.client.addnumberservicestub; import de.fu_berlin.csw.client.addnumberservicestub.add; import org.apache.axis2.axisfault; import java.rmi.remoteexception; public class AddNumberServiceClient { public static void main(string[] args) throws AxisFault, RemoteException { int s1 = 3, s2 = 4; AddNumberServiceStub stub = new AddNumberServiceStub( " // Create Request Add a = new Add(); a.setargs0(s1); a.setargs1(s2); } } System.out.println("Add " + s1 + " and " + s2); System.out.println("Resut is: " + stub.add(a).get_return());

27 Which parts can you implement as WS?

28 Conclusion Aim of this exercise: Get familiar with Web Services with Java Get familiar with SOAP and Axis2 For the exercise of next week: Use the installation tips and notes on these slides Your AAR file should provide correct Web Service You should be able to describe your source code during a live demonstration of your Web Service There are several Tutorials and Books about Apache Axis2

29 Questions? Who will present next week?

Invoking Web Services. with Axis. Web Languages Course 2009 University of Trento

Invoking Web Services. with Axis. Web Languages Course 2009 University of Trento Invoking Web Services with Axis Web Languages Course 2009 University of Trento Lab Objective Refresh the Axis Functionalities Invoke Web Services (client-side) 3/16/2009 Gaia Trecarichi - Web Languages