1. Presentation: SOAP in a distributed object framework, Application Servers & AXIS SOAP

2. 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

3. SOAP & Web Services in relation to Distributed Objects

4. SOAP and Distributed Objects
SOAP in it self has nothing to do with objects
There probably is SOAP API’s for C and COBOL
actually this also holds true for CORBA – king of OO-middleware
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

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

6. 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++
Sun’s Java Web Services Developer Pack (

7. Apache Tomcat Application Server
Apache Project is an open source initiative – widely supported by Sun & IBM (but not Microsoft)
Including a huge amount of free coding effort from both
It consist of a long range of projects including:
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
One of theese being the Apache Tomcat AS
Apache Tomcat Application Server
Capable of running JAVA applications
JSP/Servlets (reference implementation)
And projects embedded into this –
The AXIS Project
The former Apache SOAP Server
Runs embedded in Tomcat

8. Apache Tomcat AS Works on: Can be found at:
Windows, UNIX, LINUX, Mac
Can be compiled to any platform (with some work)
Can be found at:
Server listening for events:
HTTP on port 8080 (optional)
Executes Servlets/JSP and JAVA applications
AXIS is an embedded project within the Tomcat environment
Common code base!
SOAP Client
Java, C++, C#,
Delphi, VB
Application
Web Server
Apache /
MS IIS
AS/SOAP
Server
(Tomcat
with
AXIS)
JSP/
Servlet
Object
SOAP over HTTP
Web
Service
Object

9. AXIS Project Provides us with a suitable framework
Runs embedded in Apache Tomcat – just download
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 (some are still “under construction”)
Tools for WSDL Stub & Skeleton creation:
WSDL2Java &
Java2WSDL
Flexible deployment system

10. Developing applications with AXIS

11. 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

12. JWS Deploying the Calculator class
Lets assume we have an existing class we want deployed as
a Web service:
All deployment that needs to be done is to rename the java
source file, and copy it to the axis webapps root

13. And that’s it! Potential clients my read the WSDL which is
auto-generated by axis
And so – we have a
Web service listening

14. Building the dynamic client
First we must define
the end-point
Do we have all the
Arguments from the user?
Did the user choose
To subtract or add?

15. Building the dynamic client II
Convert to integer
Create a service
and a call
Set the end-point &
the operation name
Add the arguments &
set the return type
invoke the web service
Output the return value

16. Running the client
Running this:
Should result in this:

17. 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?

18. 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

19. The AXIS Project – How to Install

20. How to Install We do not need the Apache Web Server
As Tomcat has its own HTTP capabilities
Start with Apache Tomcat Application Server
Test installation is OK
Then Install the AXIS Project
I have prepared a brief installation help document to be found at the course web site