Java Web Programimi Servlet and JSP demo
Veglat JDK 1.7 MySQL 5.x MySQL Connector J Tomcat 6.x Eclipse
Building Web Applications Using Servlets and JSP Start (add) web server from tomcat Or from eclipse
A HelloWord Servlet New Dinamic Web Project HelloWord project Name Target runtime: Tomcat v7 Dynamic Web Module 2.5 Contex Name and root project WebContent On Java resources right click and add Servlet Package gui; class HelloWorld; doGet doPost Init and destroy extra info
In HelloWorld servlet class PrintWriter out = response.getWriter() Ctrl+shift+o for imports out.println("<html>"); out.println("<b>Hello World</b>"); out.println("</html>"); Go to start… Open in browser http://localhost:8080/HelloWorldProject/HelloWorld Do view source
In HelloWorld Dinamic Web Project Web content folder? New html page => HelloWorld.html Change the Title and Body content If Servlet are simply html in java Then JSP is java in html
HelloWorld JSP Add new JSP file to WebContent JSP are compiled to servlet by Tomcat Change the title and body to show the Hello World text in bold Now some Java <p> <%= "Hello world JSP from Java".toUpperCase() %> </p> <%= new java.util.Date() %> <body> <% java.util.Date today = new java.util.Date(); String toShow = "Today’s date is: "+today.toString(); %> out.println("<p>"); out.println(toShow); out.println("</p>");
Deployment Descriptors the Web.xml File File New Dynamic Project (keep defaults) Project Name Temp1 Check the Generate web.xml Add Servlet name: Test Start Url mapping is by default done directly in servlet Temp1 is context root (content folder) Test is resource name This is problematic since deployment to “real” servers will not work.
Deployment Descriptors the Web.xml File File New Dynamic Project Name: Deployment Dynamic web module version: 2.5 Keep defaults Check the Generate web.xml Add Servlet name: Hello To doGet() method add this: PrintWriter out = response.getWriter(); out.println("Hello from Servlet"); Execute the servlet Url is http://localhost:8080/Deployment/Hello The first part http://localhost:8080/ is servers address The second part is mapping which is defined in web.xml
Web.xml Is in WebContent->WEB-INF To open right click and open with text editor <welcome-file-list> … defines the home-pages Add a jsp file index.jsp to WebContent folder Go to root folder in url (http://localhost:8080/Deployment/)… Some words for servlet-name, servlet-class and servlet mapping to url-pattern Change the /Hello to /helloWorld Observe… The application server on real servers use this file in order to make real mappings
Web.xml Add login.jsp to WebContent Add a text in login.jsp “this could be a login page” In web.xml copy and paste <servlet>…</servlet-mapping> Change to <servlet-name>Login</servlet-name> And to <url-pattern>/loginpage</url-pattern> Change class-name line to => <jsp-file>demo.Hello</jsp-file> As a result: <servlet> <description></description> <servlet-name>Login</servlet-name> <jsp-file>/login.jsp</jsp-file> </servlet> <servlet-mapping> <url-pattern>/loginpage</url-pattern> </servlet-mapping>
Deployment Right click to project select export WAR file to desktop name it DeploymentDemo Copy file to …Desktop\APP\apache-tomcat-7.0.59\webapps which is the home of the tomcat http server Go to eclipse and stop local tomcat server!!! Go to Desktop\APP\apache-tomcat-7.0.59\bin and start the tomcat general server: startup.bat Go to http://localhost:8080/Deployment/ And give a try to loginpage, helloWorld Observe the folder structure of the webapps folder …
Importing Java Classes Into JSPs Import standard java classes Import your specific classes <%@ page import="java.util.Date, gui.*" %> <%= new Date() %> <% TextOutput textOut = new TextOutput(); out.println(textOut.getInfo()); %> package gui; public class TextOutput { public String getInfo() { return "This is returned from a method of a class in the gui package."; }
Getting URL Parameters http://localhost:8080/Scriptlets/index.jsp?id=4&user=bob&session=4453 Mechanism for passing data into your servlets So add new servlet named URLParameters The same applies to jsp Add new jsp file named parameters.jsp // http://localhost:8080/Scriptlets/URLParameters?id=8&user=john String user = request.getParameter("user"); String id = request.getParameter("id"); PrintWriter out = response.getWriter(); out.println("<html>"); out.println("The 'user' parameter is: " + user); out.println("<br/>"); out.println("The 'id' parameter is: " + id); out.println("</html>"); ======================== <% String name = request.getParameter("name"); // http://localhost:8080/Scriptlets/parameters.jsp?name=bob out.println("Name param is: " + name); %>
Scripting HTML Html generators <% for(int i=0; i<5; i++) { %> <p>This HTML is in a scriptlet loop, iteration: <%= i %></p> <p/> <% } %> <% String id = request.getParameter("id"); if(id == null) { %> <strong>ID parameter missing</strong> <% } else { %> ID parameter is: <%= id %>
Including Files In Other Files Create file includes.jsp Suppose you have copyright.txt file to include Static include Create copyright.txt Copyright aab.com Dynamic include updates.txt: Today's weather is: sunny JSP includes Create new jsp file: Variables.jsp <% String name = "Sue"; %> Runtime file including idnotfound.html : The ID parameter is missing. Idfound.html : The ID parameter was found. <!-- static include: content changes infrequently --> <%@ include file="copyright.txt" %> <p/> <!-- dynamic include: content changes a lot --> <jsp:include page="updates.txt" /> <!-- Must use static include if it's got java code in it that we want to access --> <%@ include file="variables.jsp" %> <%= name %> <!-- Must use include jsp tag if you don't know what file you want till run time --> <% String id = request.getParameter("id"); %> <% if(id == null) { %> <jsp:include page="idnotfound.html" /> <% } else { %> <jsp:include page="idfound.html" /> <% } %>
Forwarding and Redirecting To demonstrate forwarding add new jsp file forward.jsp Add the code from notes And observe the URL Hello <!-- Forward to another page (server side; the browser never sees forward.jsp, only index.jsp, but the url remains forward.jsp) the using jsp:forward tag --> <jsp:forward page="index.jsp"></jsp:forward> <% // forward to another page (server side) via Java // request.getRequestDispatcher("index.jsp").forward(request, response); // redirect to another page (client side) via Java. The browser will briefly // see forward.jsp, before going to the url for index.jsp // response.sendRedirect("index.jsp"); %>
Model 1 vs. Model 2 Architecture Start by creating new dynamic web project and name it MVC Add following JSP files to project login.jsp, about.jsp, error.jsp Model 1 architecture simply uses one starting jsp file and then by using forwarding and redirecting makes things work This model is unscalable and unstable so the model 2 is proposed which is also known as a MVC model Controller is servlet which makes routing So add an servlet in package controller name it Controller Now add index.jsp login.jsp => This is the login page. about.jsp => This is the about page. error.jsp => The action parameter is missing. Index.jsp => <p>This is the home page.</p> <p><a href="/MVC/Controller?action=login">Go to login page.</a></p> <p><a href="/MVC/Controller?action=about">Go to about page.</a></p> Controller.java String action = request.getParameter("action"); String page = null; if(action == null) { page = "/error.jsp"; } else if(action.equals("about")) { page = "/about.jsp"; else if(action.equals("login")) { page = "/login.jsp"; else { getServletContext().getRequestDispatcher(page).forward(request, response);