Download server side programming

Java Server Programming
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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What is a web service?
 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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How do web services work?
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)
web service registry
(UDDI)
Find the Web
service (WSDL)
Client
Publish the web service
(WSDL)
(SOAP)
Messages
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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Standard Protocols used by
Web Services
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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What is SOAP?
The basic Web services platform is XML plus HTTP.
 SOAP
 SOAP
 SOAP
 SOAP
 SOAP
 SOAP
 SOAP
 SOAP
 SOAP
 SOAP
stands for Simple Object Access Protocol
is a communication protocol
is for communication between applications
is a format for sending messages
is designed to communicate via Internet
is platform independent
is language independent
is based on XML
is simple and extensible
allows you to get around firewalls
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The Promise of Web
Services
web-based SOA as new system design paradigm
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Apache eXtensible
Interaction System (Axis)
 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
U.S. National
Hockey League,
and the service
returns the team's
current position.
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");
standings.put("central/st.louis", "3");
}
public String getCurrentPosition(String division, String team) {
String p = (String)standings.get(division + '/' + team);
return (p == null) ? "Team not found" : p;
}
}
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How to delpoy and use a web
service
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 {
public static void main(String [] args) throws Exception {
and the name
Service service = new Service();
of the method
Call call = (Call)service.createCall();
to invoke,
String endpoint = "http://localhost:8080/axis/NHLService.jws";
call.setTargetEndpointAddress(new URL(endpoint));
Prepare the
QName("getCurrentPosition"));
Arguments of the call.setOperationName(new
String division = args[0];
Method and
String team = args[1];
String position =
Invoke it
(String)call.invoke(new Object [] {new String(division), new
String(team)});
System.out.println("Got result : " + position);}}
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The Bigger Picture: Java 2
Enterprise Edition J2EE
J2EE Architecture
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J2EE Container Architecture
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Container Service APIs
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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Java Servlets
Servlets are small server-side programs
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Accessing Servlets
The Java Servlet API provides a simple framework for
building applications on web servers
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The Servlet Life Cycle
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Example of a servlet
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Servlet code cont.
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Example: HelloServelet
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The HelloServer servlet
output
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Using Form Data
Example: 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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Example: The ThreeParams
Servlet
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The Result
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Java Server Pages
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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JSP
• 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:
Thanks for ordering <I><%= request.getParameter("title") %></I>26
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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Servlets/JSP
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Servlets/JSP
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Servlets/JSP Example
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