WEB SERVICES

FIRST AND FOREMOST - LINKS Tomcat AXIS2 - NetBeans - How to setup Tomcat server in NetBeans with Axis Creating Axis2 Web Services on NetBeans Creating Web Service Client Official JEE tutorial -

JAVA AND THE (INTERNAL) WEB This is JEE (or J2EE, or Java Enterprise Edition) Most programs use client/server paradigm Instead of implementing Servers and communication code every time, there is a framework of protocols for servers that can execute Java code There are different implementations of JEE servers – Apache, Tomcat, Glassfish (and more, and more…) These servers can run multiple types of logic code Its actually more complicated than this… but lets keep it simple for now

WEB SERVICES Try to solve the problem of exposing data without the need for the server and client to be written in the same programming language (or by the same developer, or the same environments, or anything the same) How ? Server (da!?) get requests from Client (da!?!?) returns responses (well… da!?)

WEB SERVICES There are three protocols that are used here: WSDL (Web Services Description Language) - an XML file that describes the methods, parameters and return values for the service in the server XML (Extensible Markup Language) - for the data (so anyone can read it… its just text in a certain format) SOAP (Simple Object Access Protocol) - for moving (that mean serializing and sending over the net) the data between client and server Oh… all this stuff runs over HTTP protocol…

WEB SERVICES WITH AXIS2 AND TOMCAT Web services can be implemented in different languages and in each language with different implementations Were using AXIS2 But parsing XML messages and send XML messages is not enough Someone needs to handle the HTTP requests and responses (just like any web server) And for that were going to use Tomcat

TOMCAT Tomcat is a JEE web server It can run web sites But it can also runs Java code Just link ANY other web server it handles the protocol of HTTP requests and HTTP responses The Java code that runs on a JEE server is call a Servlet If we want to run web services we need a Servlet that runs it And that is AXIS2

AXIS2 AXIS2 is a code that knows how to handle Web Services requests and responses Its basically an XML parsing engine It handles web requests that the Tomcat server send to it It extracts the XML message from the HTTP request Send it to any logic we deploy in it And then do the opposite with the response Basically, is a Java code that runs Java code (that going to be YOUR code!)

THE PROCESS You write your server code (with business logic) You package it (what !?) into an AXIS web container (Packaging means taking all the compiled classes, resource and some XML files and placing them in a zip file – but with a different extenstion like JAR, WAR, AAR) You deploy this it into AXIS2 Either AXIS2 will refresh automatically or youll need to refresh it manually Thats it! (for the server part)

CLIENT/SERVER PARADIGM What does it mean to write client/server code ? It means that most of the business logic is written in the server side The server and the client have a shared context – meaning, the server knows how to dispatch different results for the same methods for different clients A Session is the term for the lifespan of a client with a server A session is alive only as long as the client is alive The clients are simple and just show the server data (in their context)

CLIENT/SERVER PARADIGM So when converting an application to run in a client/server mode, youre actually writing two programs The client side should: Have a communication layer with the server Convert the server data to its own internal model The server side should: Know how to handle multiple clients Save a context for each client session