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--- servlets [2007/10/08 16:42] – created roumani
+++ servlets [2008/02/04 19:05] (current) – roumani
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 ====== Servlets ======
+This lecture covers the JEE's approach to server-side processing. It introduces the overall Tomcat architecture and focuses on the servlet container. The hands-on lab session will walk you through the installation of Tomcat and introduces you to the capabilities of its three engines, Coyote, Catalina, and Jasper.
+===== Outline =====
+== The Architecture ==
+  * Tomcat = Coyote + Catalina + Jasper. It is a reference implementation of Sun's Servlet/JSP standards.
+  * Coyote is a connector, Catalina is a servlet container, and Jasper is a JSP compiler.
+  * Client uses HTTP to reach a Web Server which has a module (Apache) or a plug-in (IIS) for JK filtering.
+  * The web server uses NFS to serve static files, CGI to run scripts out of process, or the JK protocol to contact Coyote in process.
+  * You supply your servlet subclass to Catalina and it handles the request.
+  * Coyote today comes with an HTTP version that bypasses the JK protocol; i.e. it acts as a web server with NFS, CGI, and SSI. Hence, the whole system is self-contained and 100% Java.
+  * To enable MVC, servlets are used as controllers, POJO's and Beans for the business model, and JSP for the view.
+== The Life Cycle ==
+  * Server makes one instance of your servlet
+  * It invokes the ''init'' method on it. You may need to instantiate POJO's/beans or initialize in ''init''.
+  * It creates a pool of threads ready to invoke your servlet's ''service'' method.
+  * When a client connects, a thread is (randomly) chosen and assigned to serve this request.
+  * There is no client-to-thread mapping: the same client may get served by the same or a different thread.
+  * When it is time to stop this servlet, the server invokes its ''destroy'' method then unloads it.
+== The API ==
+  * No need to override ''service'' since it filters based on the request method. Override either ''doGet'' or ''doPost'' (or both)
+  * The request object enables you to retrieve socket data, HTTP data, the headers, the parameters, and the payload (for POST).
+  * Note that parameters are available as Map<String,String[]> and that for payloads you can have a raw stream or a wrapped up one.
+  * The response object allows you to set the HTTP response line and headers as well as the payload.
+===== To Do =====
+  * Read Sections 6.1 through 6.5 of our textbook.
+  * Take an overall look at the servlet API (accessible from our //Resources// Page.
+  * Come to Prism for a hands-on lecture