COP 4991Component Based Software

Development

Lecture #4Java Web Services

Onyeka Ezenwoye

Acknowledgement

Tapas Banerjee

Pankaj Kumar

Sang Shin

AGENDA

Java APIs for Web Services.Apache AxisWeb Services deployment.

Web Services Programming APIs

APIs for RPC-based Web Services:– JAX-RPC (Java API for XML-RPC)– Java API for XML-based RPC (JAX-RPC) sends SOAP method

calls to remote parties over the Internet and receives the results

APIs for Message-based Web Services:– JAXM (Java API for XML Messaging)– Java API for XML Messaging (JAXM) sends SOAP messages over

the Internet in a standard way

APIs for publishing and discovering Web Services:– JAXR (Java API for XML Registry)– Java API for XML Registries (JAXR) provides a standard way to

access business registries and share information

JAXR

Java API for XML RegistryEnables Java programs to access XML registries.JAXR provider:– Accesses XML registry.

JAXR client:– A client program that accesses an XML registry

using JAXR API.– Perform queries and update UDDI registries.

JAX-RPC

API for XML-based RPC

Sends SOAP method calls to remote parties over the Internet and receives the results

WSDL/XML to Java Mapping

Java to WSDL/XML Mapping

JAX-RPC Physical Architecture

Transport

SOAP

Server Side JAX-RPCRuntime System

JAX-RPC API JAX-RPC APIClient Side JAX-RPC

Runtime System

Stub

Service Endpoint

WSDL description

WSDL<->Java Mapping

Service Client

Dispatch

Container

AGENDA

Java APIs for Web ServicesApache AxisWeb Services deployment

Apache Software Foundation

Who is Apache– an open community of Java developers

worldwide.

Open Source– Lots of free software (just great!)

Downside– Lack of support– Use at your own risk

Tools &APIs: Apache Axis

Apache SOAP: First Open Source SOAP Implementation

Axis next generation Apache SOAP, New Code base – lessons learned from Apache SOAP development

Implements JAX-RPC (alternative to SUN’s JAX-RPC)

Axis Tools

Support for WSDL

Java2WSDL– for building WSDL from Java classes

WSDL2Java– for building Java proxies and skeletons from

WSDL documents

Runtime Environment

Web Server– Apache Tomcat– Allows to access Java application provided via

an HTTP server• http://jakarta.apache.org/tomcat/

SOAP engine– Apache Axis

• http://ws.apache.org/axis/

Sending requests,

getting results

Sending requests,

getting results

SOAP-awareSOAP-awareServletServlet

(e.g. Apache Axis)(e.g. Apache Axis)

SOAP-awareSOAP-awareServletServlet

(e.g. Apache Axis)(e.g. Apache Axis)

Any classprocessing

the incomingrequests

(“business logic”

Any classprocessing

the incomingrequests

(“business logic”

Any classprocessing

the incomingrequests

(“business logic”

Any classprocessing

the incomingrequests

(“business logic”

Any classprocessing

the incomingrequests

(“business logic”

Any classprocessing

the incomingrequests

(“business logic”

Any classAny classprocessingprocessing

the incomingthe incomingrequestsrequests

(“business logic”(“business logic”

Any classAny classprocessingprocessing

the incomingthe incomingrequestsrequests

(“business logic”(“business logic”

HTTP Server HTTP Server (e.g. Apache Tomcat)(e.g. Apache Tomcat)

Servlet engineServlet engine

Install & Deploy Apache Axis

Make sure that you have– J2SE SDK. We will use 1.4– A Servlet Container: We will use

Tomcat 4.1

Download axis binaries from http://xml.apache.org/axisUnzip it and look at the dir. tree. Note that Axis runs as a Servlet.

Direcotry Structure:

axis-1_0

docslibwebapps samples

axis

WEB-INF

lib

classes

web.xml

……

Apache AxisInstallation– Copy webapps\axis, paste to tomcat\webapps\– Run Tomcat: issue bin\startup from

Tomcat home.– Installation Testing http://localhost:8080/axis/

Classpathset AXIS_HOME=C:\jakarta-tomcat-4.0.6\webapps\axisset AXIS_LIB=%AXIS_HOME%\WEB-INF\libset AXIS_CP=.;%AXIS_CP%;%AXIS_LIB%\axis.jar; %AXIS_LIB%\commons-discovery.jar; %AXIS_LIB%\commons-logging.jar;%AXIS_LIB%\jaxrpc.jar; %AXIS_LIB%\saaj.jar;%AXIS_LIB%\log4j-1.2.8.jar; %AXIS_LIB%\xml-apis.jar;%AXIS_LIB%\wsdl4j.jarset classpath=%AXIS_CP%

AGENDA

Java APIs for Web ServicesApache AxisWeb Services deployment

Test the Deployment

Point your browser to http://localhost:8080/axis

Different web service creation paths

From an existing application – bottom-up– Most common. We like to expose existing back-end

systems for enterprise integration (EAI) purposes.

From WSDL, generate a completely new application – top-down– The wizards can create skeleton code from WSDL, we

then fill up the details

Combine independent web services to provide new functionality.

Creating a Web Service in Java

Typical steps:1. Create the application

2. Generate WSDL document using some Web Service tool

3. Deploy Web Service to a Web Server

4. Generate client stubs from WSDL

5. Create client application

Then publish, discover and use web service

Develop a service

Step 1 – Write a Java Class

public class AdderImpl implements Adder

{

public int add(int x, int y) throws RemoteException

{

return x + y;

}

}

public interface Adder {int add (int x, int y);

}

public class AdderImpl implements Adder

{

public int add(int x, int y) throws RemoteException

{

return x + y;

}

}

Adder.java

AdderImpl.java

Develop a service

Step 2 - Deploy to the SOAP engine – Create the deployment descriptor (*.wsdd)

<deployment xmlns="http://xml.apache.org/axis/wsdd/"

xmlns:java="http://xml.apache.org/axis/wsdd/providers/java">

<service name=“adderService" provider="java:RPC">

　　 <parameter name="className" value=“AdderImpl"/>

　　 <parameter name="allowedMethods" value=“*"/>

</service>

</deployment>

Develop a service

Step 2 - Deploy to the SOAP engine

– Copy the Java Class to the Web Server

– Start the Web Server

– Deployjava org.apache.axis.client.AdminClient *.wsdd

Develop a service

Step 3 - Check– Check (List all services) http://localhost:8080/axis/servlet/AxisServlet

Consume a service

Step 1 – Get the WSDL file of the service– Java2WSDL (usage example) java org.apache.axis.wsdl.Java2WSDL

-o adder.wsdl

-l http://localhost:8080/axis/services/adderService

-n http://cop4991/adder

adderImpl

– We use this tool because the service is built by ourselves (we have the Java Class)

outputlocation

namespace

class name

Consume a service

Step 2 – Generate the Client Stub– WSDL2Java (usage example) java org.apache.axis.wsdl.WSDL2Java myecho.wsdl

– 4 files will be generated• AdderImpl.java

• AdderImplService.java

• AdderImplServiceLocator.java

• AdderServiceSoapBindingStub.java

interface

Service factory

Service

Binding stub

Consume a service

Step 3 – Write the Client Program

…

// Make a service AdderImplService adderService = new AdderImplServiceLocator(); 　 // Now use the service to get a stub AdderImpl adder = adderService.getadderService(); 　 // Make the actual call int sum = adder.add(10,9); …

public class AdderClient{

public static void main(String[] args){

try{

//Make a service instance

AdderImplService adderService = new AdderImplServiceLocator();

//Now use the service to get a stub

AdderImpl adder = adderService.getadderService();

//Make the actual call

int sum = adder.add(10,9);

System.out.println("the sum is: "+sum);

}catch(Exception e){e.printStackTrace();}

}

}

AdderClient.java

Static Stub Client

Our client is static– Tightly bound to generated stub– Can only use one service

Dynamic Clients– Use WSIF (Web Service Invocation

Framework) instead

Resources

Apache Tomcat– http://jakarta.apache.org/tomcat/

Apache Axis Home– http://xml.apache.org/axis

XMethods– http://www.xmethods.net