Presentation:SOAP/WS in a distributed object framework,

Application Servers & AXIS SOAP

Outline

• SOAP and Web Services in relation to Distributed Objects

• The AXIS Project – Open Source Java SOAP Server• Introduction to the Apache Tomcat Application Server

• Introduction to the AXIS Project

• How to code a very simple example

• How to install

SOAP & Web Services in relation to Distributed Objects

SOAP and Distributed Objects

• SOAP in it self has nothing to do with objects

• The trick is the supporting API’s converting objects to WSDL and SOAP for serialization across the network

• Using the Proxy Pattern for decoupling

• We shall be looking at Microsofts .NET Web service technology (using Microsoft Visual Studio .NET) at a later point, while we now will focus on the open source community, targeting specifically Java with the AXIS toolkit

Frameworks for Web Services &The AXIS Project – Open Source Java SOAP Server

How to make a Web service with SOAP

• You need an application or API capable of supporting:• Communication over the Internet (HTTP)• Security (SSL)• XML Parsing capabilities• Tools for WSDL handling / stub generation• and more

• Two examples of this:• Apache Tomcat Application Server with AXIS• Microsoft Internet Information Server with .NET

• We will use them both – though starting with the Apache Tomcat Application Server and the AXIS project – this will be introduced here• Other Web service frameworks:

• AXIS for C++, Metro (Java)• Sun’s Java Web Services Developer Pack (

http://java.sun.com/webservices/index.jsp)

Apache Tomcat Application Server

• Apache Project • Open source initiative • Widely supported by Sun & IBM (but not Microsoft)• Including a huge amount of free coding effort from both

• Apache Web Server• The most used web server in the world (and its free!)• The most secure, with SSL cap., and NT, Linux & UNIX support• Huge amount of ”plug-in” modules

• Apache Tomcat Application Server• Capable of running JAVA applications• JSP/Servlets (J2EE reference implementation)• And projects embedded into this –

• The AXIS Project• The former Apache SOAP Server• Runs embedded in Tomcat / other J2EE

Apache Tomcat AS

• Works on:• Windows, UNIX, LINUX, Mac• Can be compiled to any platform (with some work)

• Can be found at:• http://jakarta.apache.org/tomcat/index.html

• Server listening for events: • HTTP on port 8080 (optional)• Executes Servlets/JSP and JAVA applications• AXIS is an embedded project within the Tomcat environment

SOAP ClientJava, C++, C#,

Delphi, VB Application

SOAP ClientJava, C++, C#,

Delphi, VB Application

SOAP over HTTPSOAP over HTTP

Web ServerApache /MS IIS

Web ServerApache /MS IIS

AS/SOAPServer

(Tomcat with

AXIS)

AS/SOAPServer

(Tomcat with

AXIS)

JSP/ServletJSP/

Servlet

WebService

WebService

ObjectObject

ObjectObject

Common code base!Common code base!

AXIS Project

• Provides us with a suitable framework• Runs embedded in Apache Tomcat – just download

• http://xml.apache.org/axis/• But can run on ANY J2EE compliant Application Server

• BEA Weblogic, IBM WebSphere, Sun Java System Application Server

• Supports full WSDL• Supports SOAP communication via:

• HTTP, SMTP, FTP and open for extension• Build in security, log, error and fault handling • Tools for WSDL Stub & Skeleton creation:

• WSDL2Java &• Java2WSDL

• Flexible deployment system

Developing applications with AXIS

How to get started

• As opposed to Java RMI and CORBA, we do not necessarily have to start with the interface

• All we need is a Java class or interface, and the toolkit will generate the WSDL interface for us

• We call this the JWS (Java Web Service) Instant Deployment scenario

• This approach has some limitations however, as we shall look into at a later point, but for now lets try this out

JWS Deploying the Calculator

Lets assume we have an existing class we want deployed asa Web service:

All deployment that needs to be done is to rename the java source file, and copy it to the axis webapps root

And that’s it!

And so – we have aWeb service listening

Potential clients my read the WSDL which isauto-generated by axis

Building the dynamic client

First we must definethe end-point

Do we have all theArguments from the user?

Did the user chooseTo subtract or add?

Add the arguments &set the return type

Building the dynamic client II

Convert to integer

Create a serviceand a call

Set the end-point &the operation name

invoke the web service

Output the return value

Running the client

Running this:

Should result in this:

That was easy!

• Yes – but not beautiful• Won’t this become very complex with non trivial Web

services?• Problem when parameters are non-atomic types

• Handling of references?

• Where has the Access Transparency gone?• What about Location Transparency?

Lessons to be learned

• We have actually made our own “client proxy stub” • Can you make your own “client proxy stub” – so that

the client application becomes “access transparent”? • In fact, we shall look closer at the toolkits abilities next

time and the more advanced features• Also, the JWS Instant Deployment is only for simple

class structures, it will not be as easy otherwise

The AXIS Project – How to Install

How to Install

• We do not need the Apache Web Server• As Tomcat has its own HTTP capabilities

• Start with Apache Tomcat Application Server• http://jakarta.apache.org/tomcat/index.html

• Test installation is OK• Then Install the AXIS Project

• http://xml.apache.org/axis/

• I have prepared a brief installation help document to be found at the course web site

Tools to Use

• Please use Notepad and Command prompt for now!• Later we will be using NetBeans

Other Java WS Toolkits

• Metro:• Appears to be more mature then AXIS

• https://metro.dev.java.net/

• Interop test with WCF: http://weblogs.java.net/blog/haroldcarr/archive/2008/03/metro_web_servi_2.html