Intro to Apache Axis Siva Jagadeesan

About Me I am a Java Consultant working in a project for Deloitte Consulting My fields of Expertise –J2EE Technologies –Java tools for Extreme Programming (Ant, JUnit etc) My fields of Interest –Web Services –J2ME –Aspect Oriented Programming

Agenda Web Services Basics Intro to Apache Axis

Outline Web Services Basics –What is Web Service? –Web Services Architecture –XML Messaging XML-RPC SOAP –What is WSDL? –Development plan for Service Requestor –Development plan for Service Provider

Outline Intro to Apache Axis –What is Apache Axis? –Architecture of Apache Axis –Features of Apache Axis –Installing Apache Axis –Publishing Web Service through Apache Axis –Walkthrough of deploying and accessing a simple web service using Apache Axis

What is Web Service? A Web Service is any service that – is available over the web – uses standardized XML messaging – is OS and Programming language independent

Web Services Architecture There are two ways we can view Web Services architecture 1.Web Service Roles 2.Web Service Protocol Stack

Web Service Roles There are three major roles Service Registry Service Requestor Service Provider 2) Discover services 3) Invoke service Provider of the Web Service Consumer of the Web Service Logically Centralized directory of services 1) Register service

Web Service Protocol Stack Discovery UDDI Description WSDL XML Messaging XML-RPC,SOAP,XML Transport HTTP,SMTP,FTP,BEEP Responsible for centralizing services Responsible for transporting messages Responsible for describing the public interface to a specific web service Responsible for encoding messages in common XML format

XML Messaging There are two ways of XML Messaging XML-RPC SOAP

What is XML-RPC ? is a simple protocol that uses XML messages to perform RPC Request are encoded in XML and send via HTTP Response are encoded in XML and received via HTTP is a easiest way to get started with web services

Sample XML-RPC Request com.agram.sayHello Java

Sample XML-RPC Response Hello Java

What is SOAP? Simple Object Access Protocol SOAP is slightly more complicated than the XML-RPC SOAP extended XML-RPC It uses XML namespaces and XML Schemas.

SOAP Message Envelope is like a wrapper for content Header is a optional element that could contain control information Body element includes requests and responses Body element will include a Fault element in the event of an error SOAP Message Envelope Header Body

Sample SOAP Request <SOAP-ENV:Envelope xmlns:xsd=" xmlns:SOAP-ENV= xmlns:xsi=" <ns1:sayHello xmlns:ns1=" Java

Sample SOAP Response <SOAP-ENV:Envelope xmlns:xsd=" xmlns:SOAP-ENV= xmlns:xsi=" <ns1:sayHelloReponse xmlns:ns1=" Hello Java

What is WSDL? Web Services Description Language Has 6 major elements 1.definitions – defines the name of the web service 2.types – describes all the data types that will be transmitted 3.message – defines the name of the message that will be transmitted 4.portType – defines the operations 5.binding – defines how the message will be transmitted 6.service – defines where the service is located

Development plan for Service Requestor 1) Find web service via UDDI 2) Retrieve service description file 3) Create XML-RPC or SOAP client 4) Invoke remote service

Development plan for Service Provider 1) Create the core functionality 2) Create XML-RPC or SOAP service wrapper 3) Create service description file 4) Deploy service 5) Register new service via UDDI

What is Apache Axis? “Axis is essentially a SOAP engine – a framework for constructing SOAP processors such as clients, servers, gateways etc” - Axis Website

Architecture of Apache Axis

1. Admin Sub-system handles administration and configuration of the server 2. Service Sub-system implements the RPC exchange protocol 3. Provider Sub-system is the interface between Axis server and the external component methods that are to be exposed as webservice 4. Transport Sub-system receives and delivers the message from the service sub system 5. Encoding Sub-system manages encoding/decoding and serilization/deserilization between XML data types and Java Classes 6. Message Sub-system defines the structure of the different elements of a SOAP message and provides functionality for binding and parsing the different elements of these messages

Features of Apache Axis Successor to Apache SOAP It can run as a standalone server or as an a server that plugs into Servlet engine like Tomcat Automatic WSDL generation for deployed services Java2WSDL – to generate WSDL from Java interface WSDL2Java – to generate Java classes from WSDL Easy deployment Uses JAX-RPC API

Installing Apache Axis 1) Download Axis Distribution archive from - Axis distribution archive contains a web application ( webapps/axis/ directory) for hosting an Axis Server in a web container like Tomcat

Installing Apache Axis (Cont) 2) Deploy Axis Server in the Tomcat 4.X server a) Copy Axis Web application (webapps/axis directory) to $TOMCAT_HOME/webapps b) Copy jaxrpc.jar (that is provided with Axis distribution) and xerces.jar ( or any other XML parser) to $TOMCAT_HOME/common/lib jaxrpc.jar and xerces.jar includes classes with “java” and “javax” packages and Tomcat does not authorize to load any classes in that package from WEB-INF/ lib directory of the web application.

Installing Apache Axis (Cont) 3) Configure the environment by including these libraries in the CLASSPATH - log4j-core.jar - commons-logging.jar - wsdl4j.jar - jaxrpc.jar - tt.bytecode.jar - xerces.jar ( or any other XML Parser)

Validating the Installation 1) Start the Tomcat Web Server 2) Goto - you should be able to see Apache-Axis start page - if you did not, then the axis is not correctly installed or the web server is not running 3) Goto - this test page verifies whether all the needed and optional libraries are present. - Axis will not perform properly until all the needed libraries are present.

Publishing Web Service through Apache Axis The two ways we can publish a web service with Axis are, 1.Instant Deployment – Java Web Service (JWS) 2.Custom Deployment – Using Web Service Deployment Descriptor ( WSDD)

Walkthrough of deploying and accessing a simple web service using Apache Axis

The steps we will walkthrough 1. Code – code a simple HelloWorld java class that we want to expose as web service 2. Java2WSDL – Generate the WSDL file for the given HelloWorld Interface 3. WSDL2Java – Generate the Server side wrapper class and stubs for easy client access 4. Deploy – deploy the service to apache axis 5. Client – code a simple client that access our HelloWorld Web Service

Step 1: Code HelloWorld.java package helloworld; public interface HelloWorld { public String sayHello( String name); }

Step 1: Code (Cont) HelloWorldImpl.java package helloworld; public class HelloWorldImpl implements HelloWorld { public String sayHello( String name){ if(name == null) return “Hello Everyone”; else return “Hello “ + name; }

Step 2: Java2WSDL This command will generate the WSDL that Conforms to our interface % java org.apache.axis.wsdl.Java2WSDL -o hello.wsdl -l -n urn:helloworld -p“helloworld" urn:helloworld helloworld.HelloWorld Parameters description -o = Name of the output -l = URL of the web Service -n = Target Namespace for the WSDL -p = Map Java package to namespace Fully Qualified Class Name

Step 3: WSDL2Java This command will generate the wrapper code for deploying the service, as well as client stubs for accessing it. % java org.apache.axis.wsdl.WSDL2Java -o. -d Session -s -p helloworld.gen hello.wsdl Parameters description -o = Base output Directory -d = Scope of deployment -s = To generate Server-side code too -p = Package to place the code Name of the WSDL

Step 3: WSDL2Java These are the codes that will get generated 1. HelloWorldSoapBindingImpl.java – This is the implementation code for the Web Service 2. HelloWorld.java – This is the remote interface 3. HelloWorldService.java – This is the service interface 4. HelloWorldServiceLocator.java – Helper class to retrieve handler to service 5. HelloWorldSoapBindingSkeleton.java – Server-side skeleton code 6. HelloWorldSoapBindingStub.java – Client side stub 7. deploy.wsdd – axis deployment descriptor 8. undeploy.wsdd – deployment descriptor to undeploy the web services from the Axis System

Step 3: WSDL2Java HelloWorldSoapBindingImpl package helloworld.gen; public class HelloWorldSoapBindingImpl implements helloworld.gen.HelloWorld { public String sayHello(String str0) throws java.rmi.RemoteException { } import helloworld.HelloWorldImpl; HelloWorldImpl helloWorld = new HelloWorldImpl(); return helloWorld.sayHello(str0);

Step 4: Deploy 1. Compile the Service Code % javac helloworld\gen\*.java 2. Package the code for Axis % jar cvf hello.jar helloworld/*.class helloworld/gen/*.class % mv hello.jar $TOMCAT_HOME/webapps/axis/WEB-INF/lib 3. Deploy the Service using WSDD % java org.apache.axis.client.AdminClient deploy.wsdd Done processing

Step 5: Client package helloworld; Import helloworld.gen.*; public class HelloWorldTester { public static void main(String [] args) throws Exception { // Make a service HelloWorldService service = new HelloWorldServiceLocator(); // Now use the service to get a stub to the service helloworld.gen.HelloWorld hello = service.getHelloWorld(); // Make the actual call System.out.println( hello.sayHello(“Java Gurus”) ); }

Summary Web Service –Roles in Web Services –Web Services Protocol Stack –Different ways of XML Messaging –Development plan for Service Requestor and Provider Axis –Architecture of Axis –Features of Apache Axis –Installing Apache Axis –Different ways of deploying Web Service with Axis –Deploying and accessing a simple web service using Apache Axis

Resources JAX-RPC home Web Services & Java home Java Web Services tutorial Apache Axis SOAP WSDL

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