 Lecture 1 focuses on:
 Introduction to web services
 Web Services using Axis
 The bigger Picture: Introduction to J2EE
 Java Servlets
 Java Server Pages (JSP)
 Servlets/JSP
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 A web Service is a server side application component accessible via web protocols (HTTP over
TCP)
 It provides services and data to remote clients and other applications
 It provides a generic and standardized support for client-server paradigm accessible via the web
 The idea behind web services came about to allow big corps like Microsoft to provide a web service registry, and then you'd pay (on a per-use basis) for every web service you wanted to use (as opposed to having individual applications installed on your computer
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Clients communicate with the web service via XML messages based on a protocol called SOAP ( encoding and decoding messages in XML is supported by Apache Axis)
Find the Web service (WSDL) web service registry
(UDDI)
Client
(SOAP)
Messages
Publish the web service
(WSDL)
Web service
Provider
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More on Web Services
 loosely coupled, reusable components
 encapsulate discrete functionality
 distributed
 programmatically accessible over standard internet protocols
 add new level of functionality on top of the current web
 Web services are self-contained and selfdescribing
 Web services can be discovered using UDDI
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 UDDI -- The "Universal Description, Discovery and Integration" protocol. A protocol for publishing web service descriptions
 WSDL – “Web Service Description Language” is a description language: using XML that describes exactly what your web service does
 SOAP – “Simple Object Access Protocol” A transport protocol that sends XML messages using HTTP (which runs on top of TCP, usually on port 80)
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The basic Web services platform is XML plus HTTP.
 SOAP stands for Simple Object Access Protocol
 SOAP is a communication protocol
 SOAP is for communication between applications
 SOAP is a format for sending messages
 SOAP is designed to communicate via Internet
 SOAP is platform independent
 SOAP is language independent
 SOAP is based on XML
 SOAP is simple and extensible
 SOAP allows you to get around firewalls
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web-based SOA as new system design paradigm
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 Axis supports the interaction between the client and the server (the web service)
 Axis is an implementation of the SOAP protocol. It shields the developer from the details of dealing with SOAP and
WSDL
 You use Axis on the server side to write your web service
(and deploy it as a Tomcat webapp)
 At the client side, Axis sends SOAP messages to invoke the methods of the server (using remote procedure calls)
 Axis lets the client make the method calls on the web service object as if it were a local object (AXIS generates a WSDL for the web service)
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import java.util.*;
Example: A simple Web
Service. Lets the user gives the name of one of the teams in the public class NHLService {
HashMap standings = new HashMap(); public NHLService() {
// NHL - part of the standings as per 04/07/2002 standings.put("atlantic/philadelphia", "1"); standings.put("atlantic/ny islanders", "2"); standings.put("atlantic/new jersey", "3"); standings.put("central/detroit", "1"); standings.put("central/chicago", "2"); U.S. National
Hockey League, and the service standings.put("central/st.louis", "3");
} public String getCurrentPosition(String division, String team) {
String p = (String)standings.get(division + '/' + team); returns the team's current position.
return (p == null) ? "Team not found" : p;
}
}
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 The steps needed to create and use the
"getCurrentPosition" web service.
 First you copy the NHLService.java file into the
Axis directory on your web server
 Then you rename the file to NHLService.jws
(JWS stands for Java Web Service).
 The web service is now deployed
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package hansen.playground;
The client import org.apache.axis.client.Call; needs to specify import org.apache.axis.client.Service; import javax.xml.rpc.namespace.QName; is the URL of import java.net.*; the jws-file public class NHLServiceClient { and the name public static void main(String [] args) throws Exception {
Service service = new Service(); of the method
Call call = (Call)service.createCall(); to invoke,
String endpoint = "http://localhost:8080/axis/NHLService.jws";
Prepare the call.setTargetEndpointAddress(new URL(endpoint)); call.setOperationName(new QName("getCurrentPosition")); Arguments of the
String division = args[0];
Method and
String team = args[1];
Invoke it
String position =
(String)call.invoke(new Object [] {new String(division), new
String(team)});
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System.out.println("Got result : " + position);}}

 J2EE Architecture
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 Example: create audio component, publish its name in a naming service (JNDI) available to your application. This provides a simple method to access the service APIs
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 Servlets are small server-side programs
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 The Java Servlet API provides a simple framework for building applications on web servers
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Example of a servlet
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An HTML Form With Three
Parameters
<FORM ACTION="/servlet/coreservlets.ThreeParams">
First Parameter: <INPUT TYPE="TEXT" NAME="param1"><BR>
Second Parameter: <INPUT TYPE="TEXT" NAME="param2"><BR>
Third Parameter: <INPUT TYPE="TEXT" NAME="param3"><BR>
<CENTER><INPUT TYPE="SUBMIT"></CENTER>
</FORM>
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 JSP , an extension of the servlet technology, is a text based document (name.jsp) that contains two parts
 HTML or XML for static content
 JSP tags and scriplets in Java that generates the dynamic content
 The web container converts the JSP page into a servlet class and compiles it
Example of scriplets:
<%! private int someField = 5; %>
<%! private void someMethod(...) {...} %>
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• JavaServer Pages (JSP) lets you separate the dynamic part of your pages from the static HTML.
• Simply write the regular HTML in the normal manner, using whatever Web-page-building tools you normally use
• then enclose the code for the dynamic parts in special tags, most of which start with "<%" and end with "%>".
•For example, here is a section of a JSP page that results in something like "Thanks for ordering Core Web
Programming " for a URL of http://host/OrderConfirmation.jsp?title=Core+Web+Program ming :

The ThreeParams example in JSP
<HTML>
<TITLE>INPUT FORM</TITLE>
<BODY>
First Parameter-: <%=request.getParameter("param1")%> <BR>
Second Parameter-:<%=request.getParameter("param2")%> <BR>
Third Parameter-: <%=request.getParameter("param3")%> <BR>
</BODY>
</HTML>
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