Download 236369 WS2

Web Services – Part II
CS 236369, Spring 2010
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Axis : Apache EXtensible
Interaction System
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What is AXIS(2)?
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The Apache Axis2 project is a Java-based implementation
of both the client and server sides of the Web services
equation.
Axis is essentially a SOAP engine – a framework for
constructing SOAP processors
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client side
server side
It enables you to :
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Send, receive and process SOAP messages
Create a Web service out of a plain Java class
Create implementation classes for both the server and client using
WSDL
Easily retrieve the WSDL for a service
Create or utilize a REST-based Web service
And more…
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Remote Method Invocation is not
New
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java.rmi has been in Java since Java’s early versions
In Java RMI, objects can invoke methods of objects that
reside on a remote computer
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(RMI = Remote Method Invocation)
So, what has been changed?
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Using HTTP for communication
Using agreed protocols, Java can invoke methods that were not
written in Java (e.g., .NET methods) and vice versa
A complex registry procedure has been required in RMI
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What We Would Like to Create
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Client applications: applications that can call a
remote Web service
Services: methods that can be called by remote
applications
Service descriptions: WSDL files that describe
our methods
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Live Demo
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We will build a web service (both server and
client side) using Eclipse WTP (already integrated
in your J2EE Eclipse version)
We will use AXIS2 version 1.3
The demo is based on “Eclipse WTP Tutorials Creating Bottom Up Web Service via Apache
Axis2” with some extensions
Guidlelines appear in the following slides
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Installin AXIS2 Version 1.3 in Eclipse
1.
2.
Download AXIS2 version 1.3 binary distribution (use this link)
Set it in Eclipse: Window  Preferences  Web Services 
Axis2 Preferences
Client Applications
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Calling Web Services
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By now, we already know how to invoke a remote
Web service in Java:
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Open a socket to the remote server
Through the socket, send a SOAP request wrapped by a
HTTP request
Parse the response (e.g., using SAX/DOM)
However, this approach is cumbersome, and most
of it can be automated
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This is the whole point of using standards…
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Web Services Explorer
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We have a power calculation Web service running on the course server at:
http://ibm411.cs.technion.ac.il/PowerService/services/PowerCalculation?wsdl
We will use Eclipse web services explorer in order to explore it before we write a
client for that WS. (Under Run  Launching the Web Services Explorer)
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Parameters
values for the
power function
(a^n)
The result
It’s all SOAP
underneath
The WSDL2Java Application
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Axis provides a mechanism for communicating
with a Web service using stubs
That is, generation of regular Java classes that
have an interface similar to that of the Web
service and implementation that wraps Web
service management
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Creating a new Web service client
project
Settings
The WSDL
location on
IBM411
Axis 2
Deploy level
Project name
(Dynamic Web
Application)
The client class
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Added by the programmer using the classes (stubs) generated by the
WSDL2Java:
package cs236607ws;
import cs236607ws.PowerCalculationStub.Power;
import cs236607ws.PowerCalculationStub.PowerResponse;
public class PowerClient {
public static void main(String[] args) {
try {
int a = 3;
int n = 4;
You can
specifically
set the Web
Service end
point URL
PowerCalculationStub stub = new PowerCalculationStub();
//Define the end point URL:
//PowerCalculationStub stub = new PowerCalculationStub
//("http://localhost:8080/
//
PowerService_20100613I/services/PowerCalculation?wsdl");
Power p = new Power();
p.setA(a);
p.setN(n);
PowerResponse res = stub.power(p);
System.out.println("The result of " + a + "^" + n + " is: "
+ res.get_return());
} catch (Exception e) {
System.out.println(e.getStackTrace());
}
}
{
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Project Hierarchy
Created by
WSDL2Java
Created by
programmer (previous
slide). Not necessarily
in same package
AXIS2 configuration
Deployment Descriptor
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Server Applications
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Creating a Web Service
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We will begin with a service example. Given the
base and the exponent (integers), our simple
service will calculate the result. This is the class:
package cs236607WS;
public class PowerCalculation {
public int power(int a, int n) {
return (int) Math.pow(a, n);
}
}
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Creating a new Dynamic Web project
Projext Settings
Runtime (Tomcat
server)
Project facets
configuration – next
slide
Project Facets Configurations
Mark Axis2 facet
Create Package + Class (and build the
project)
Make it a Web service – Create a new
Web service project
Settings
“Start” service
level
Bottom up,
meaning you
start from Java
up to WSDL
The class we
created
Runtime Tomcat
Set to Axis2 !!!
Press it after
the settings
The project we
created
Run
What is wrong?
Correct URL
Let’s look on
the Services
EPR = End Point Reference
Click to view the created
WSDL
The Service WSDL
Axis automatically provides a WSDL for each
deployed service
 To get the WSDL, use the service URL with the
empty argument wsdl
http://localhost:8080/PowerServiceExample/service
s/PowerCalculationWS?wsdl
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How Does it Work?
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The Servlet AxisServlet of this application is
responsible for invoking services
All URLs of the form /services/* are mapped to
the AxisServlet
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Where is it written?
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How Does it Work? (Cont.)
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When a SOAP request arrives, the AxisServlet
object parses the request and invokes the
corresponding method of the class associated with
the service URL (According to the services that
were deployed)
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Deploying The Service
One option, in which you include the entire axis2
application is:
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Export the completed project to WAR
Put this WAR under Tomcat webapps directory
That’s it!
Usually this is not required, and all you need to deploy
is the service only, while axis2 is already deployed.
For this you will need to put axis2.war file under
$CATALINA_BASE/webapp/
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Download AXIS2 version 1.3 WAR distribution (use this
link)
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Service Archive File
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Now you need to bundle the service files together into a service
archive file.
The ‘manual’ way:
Create an empty folder.
Create a directory called "META-INF" inside that.
Put services.xml into the META-INF directory. (this file will be
discussed later)
If you have the WSDL file corresponding to the Web service, rename
it to service.wsdl and put that into the same directory. (It is not
necessary to have a wsdl file in Axis2.)
If you want any third-party lib files or you own lib files, crate a
directory called "lib" in the same level as META-INF, and drop all
your lib files into that.
Copy the compiled service implementation classes into the directory.
Create a zip file from all those files and rename it to *.jar or *.aar.
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Service Archive File (Cont.)
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The ‘automatic’ way - use service archive
generator Eclipse Plug-in
Once you have the service archive file (aar) drop
it into the services sub directory in the Axis2
repository
($CATALINA_BASE/webapp/axis2/WEBINF/services )
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Service Configuration - services.xml
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The description of services is specified using
services.xml.
Each service archive file should have a
services.xml in order to be a valid service and it
should be available in the META-INF directory of
the archive file.
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In Eclipse it was created for you.
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Services.xml example:
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Service Configuration - services.xml
(Cont.)
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Among the attributes & elements of services.xml
are:
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Name (service element attribute): The service name
will be the name of the archive file if the .aar file
contains only one service, or else the name of the
service will be the name given by the name attribute.
Scope (service element attribute): The time period
during which runtime information of the deployed
services will be available. The default value (if you
don't enter any value) will be "Request“.
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Service Configuration - services.xml
(Cont.)
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Axis2 configuration page
A short tutorial about writing your own
services.xml
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Resources
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AXIS2 1.3 Download
Eclipse WTP Tutorials - Creating Bottom Up
Web Service via Apache Axis2
HU
Developer.com
Axis2 Documentation
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