IS907 Java EE Java Servlets What is a

IS-907 Java EE Java Servlets

What is a servlet? • A server extension/plugin • A servlet implements the Servlet interface • Many servlets are subclasses of Http. Servlet • Http servlets produce http responses • Most http servlets write html pages Even Åby Larsen (even. larsen@uia. no) IS-102 Introduksjon 2

How do Http. Servlets work • Each servlet is bound to a unique url • It has methods to handle each type of http request • When the servlet container receives a request • • it finds the servlet bound to the url • and calls the servlet’s method corresponding to the request type The servlet does some computations (probably) • • and writes the response, typically a html page When the servlet’s method returns, the container sends the response to the browser Even Åby Larsen (even. larsen@uia. no) IS-102 Introduksjon 3

Writing Http Servlets • Make a subclass of Http. Servlet: @Web. Servlet(name="Hello. Servlet", url. Patterns="/hello") public class Hello. Servlet extends Http. Servlet {. . . } • The Web. Servlet annotation • identifies the class as a servlet class, • specifies an internal name, • and a url pattern • The default value for both name and url. Patterns is the class name Even Åby Larsen (even. larsen@uia. no) IS-102 Introduksjon 4

Writing Http Servlets continued. . . • Override one or more of the request handling methods (usually do. Get() and/or do. Post(): protected void do. Get(Http. Servlet. Request request, Http. Servlet. Response response) throws Servlet. Exception, IOException { // do whatever has to be done to handle // an http get request } Even Åby Larsen (even. larsen@uia. no) IS-102 Introduksjon 5