Tomcat Jan 14 2019 The Apache Jakarta Project The Apache Jakarta Project creates and maintains open source solutions on the Java platform for distribution to the public at no charge Apache Jakarta Tomcat or just Tomcat is one of those projects Tomcat is a container for servlets Tomcat can act as a simple standalone server for Web applications that use HTML servlets and JSP Apache is an industrial strength highly optimized server that can be extended with Tomcat 2 Getting Tomcat The Apache Jakarta website is hard to navigate If you want to get Tomcat one reasonable download site is http mirrors xtria com apache jakarta tomcat5 v5 0 29 bin You would need the whole tarball which will have a name such as jakarta tomcat 5 0 29 tar gz An excellent tutorial site is Configuring Using Apache Tomcat http www coreservlets com Apache Tomcat Tutorial This site also contains many examples you can use to test your installation Installing Tomcat by itself is much easier than installing Apache and then adding Tomcat to it 3 Web apps A web application is basically a web site that A web application can consist of multiple pieces Knows who you are it doesn t just give you static pages it interacts with you Can permanently change data such as in a database Static web pages possibly containing forms Servlets JSP Tomcat organizes all these parts into a single directory structure for each web application but you have to help with the organization 4 Directories To create servlets you really should have two directory structures Tomcat requires a particular set of directories for your web application A development directory in which you can write and partially debug your code A deployment directory in which you put live code It is extremely picky about having everything in the right place Since your web application must typically co exist with other web applications you should use packages to avoid name conflicts This further complicates the Tomcat directory structure 5 Packages A package statement in Java must be the very first line of code in the file Example package com example model import javax servlet import javax servlet http import java io public class MyServlet extends HttpServlet This implies that This program is in a file named MyServlet java which is in a directory named model which is in a directory named example which is in a directory named com 6 Tomcat directory structure myApplicationDirectory this is your top level directory myWebForm html myJspPage jsp WEB INF must have this directory named exactly like this lib mostly for external jar files classes must have this directory named exactly like this com The com example model package directory example model myModel class in package com example model web myServlet class in package com example web web xml this is the deployment descriptor it must have this name 7 My files myWebForm html com example web myServlet class This does the business logic it is good form to keep it separate myJspPage jsp This is the servlet I intend to use it will use the myModel class but to do this it needs an import statement import com example model myModel com example model myModel class This is the web page with a form that starts up the servlet The optional JSP page to create the HTML output could be done directly by myServlet web xml A file required by Tomcat to tell it what class to start with and how to refer to that class 8 myWebForm html html body form method POST action NameSeenByUser do various form elements form body html 9 web xml xml version 1 0 encoding ISO 8859 1 web app xmlns http java sun com xml ns j2ee xmlns xsi http www w3 org 2001 XMLSchemainstance xsi schemaLocation http java sun com xml ns j2ee web app 2 4 xsd version 2 4 servlet servlet name Some internal name servlet name servlet class com example web MyServlet servlet class servlet servlet mapping servlet name Some internal name servlet name url pattern NameSeenByUser do url pattern servlet mapping 10 Servlet without JSP public class MyServlet extends HttpServlet public void doPost HttpServletRequest request HttpServletResponse response throws IOException ServletException response setContentType text html PrintWriter out response getWriter String value request getParameter name out println html body I got name 11 Servlet with JSP public class MyServlet extends HttpServlet public void doPost HttpServletRequest request HttpServletResponse response throws IOException ServletException String value request getParameter name computation resulting in some Object obj request setAttribute objName obj RequestDispatcher view request getRequestDispatcher result jsp 12 JSP result jsp page import java util html head title Your results title head body MyObject object MyObject request getAttribute objName String someResult computations using object out print br And the answer is someResult body html 13 Flow The user submits an HTML form Tomcat finds the servlet based on the URL and the deployment descriptor web xml and passes the request to the servlet The servlet computes a response Either Or The servlet writes an HTML page containing the response The servlet forwards the response to the JSP The JSP embeds the response in an HTML page Tomcat returns the HTML page to the user 14 Alternatives to Tomcat Sun s Java Web Server Java Web Server Development Kit JWSDK Old no longer being developed all in Java Official reference implementation Difficult to install and configure JBoss Open source Opinions vary on how easy it is to install Comes with built in database 15 The End 16
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