presentation: soap/ws in a distributed object framework, application servers & axis soap
TRANSCRIPT
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 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
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
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
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
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