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Added folder for video notes, easy to find
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‎VideoNotesCopy/VideoNotes_1.txt

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Author: Ross Studtman
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Tutorial: John Purcell's "Servlets and JSPs: Creating Web Applications With Java"
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John's website: CaveOfProgramming.com
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Notes for videos 3 through 7
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Video #3: Creating a servlet
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Video #4: Creating a JSP page
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Video #5: Understanding the web.xml file
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Video #6: Deploying servlet to local Tomcat server.
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Video #7: Deploying to internet.
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VIDEO #3 Notes:
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Create a servlet.
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I created the following to demonstrate this:
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* gui -- a package
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* Video_3_servlet.java -- inside gui package
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[ ] Video_3_servlet.java
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Notice the doGet() and doPost() methods receive two arguments:
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HttpServletRequest request, HttpServletResponse response
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We can use these objects for a variety of things. Such as creating a PrintWriter object.
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doGet():
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Create a PrintWriter object:
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PrintWriter out = response.getWriter();
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Create some output so when this servlet is run we see a result:
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out.println("<html>");
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out.println("<h1>Greetings from the doGET method!!</h1>");
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out.println("</html>");
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Run the servlet:
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Select the servlet's tab in Eclipse, click the green run button in Eclipse's toolbar.
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First time running it you'll get a dialog pop up:
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Choose existing server radio button;
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Select Tomcat v7.0 Server at localhost (it's State says "Started");
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Always use this server when running this project check box;
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Another dialog may pop up: "Server: The server may need to be restarted. Do you want to..."
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Restart server radio button;
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Remember my decision check box;
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Notice the address bar in the browser:
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http://localhost:8080/JSP_Tutorial_1/Video_3_servlet
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http://localhost:8080 --> domain
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JSP_Tutorial_1 --> context root
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Video_3_servlet --> servlet
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If you open another browser and paste in that address you'll get the same result.
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That is, this *is* the URL address for reaching this servlet.
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VIDEO #4 Notes:
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Creating a .jsp file.
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John notes that it is not "normal" to spit out HTML directly from the java program as we did
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in Video #3. Normally the HTML is found inside a JSP file. JSPs are where your HTML goes.
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In the JSP_Tutorial_1 project folder is the WebContent folder and this is where .jsp files
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should go.
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I created the following for this tutorial:
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* Video_4_htmlFile.html
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* Video_4_jspFile.jsp
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[ ] Video_4_htmlFile.html
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This is a regular, plain Jane HTML file.
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R-click WebContent -> New -> HTML: name it.
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Run your HTML file:
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Select the tab in Eclipse, click green run button.
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Admire your HTML in the browser.
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[ ] Video_4_jspFile.jsp
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R-click WebContent -> New -> JSP File: name it.
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A JSP page is an HTML page into which you can embed java code. JSPs are compiled into servlets
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by the application server (Tomcat).
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This is an expression tag:
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<%= stuff goes here %>
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The expression tag will write directly to the HTML page. Put strings in here.
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For example, this:
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<%= new java.util.Date() %>
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will invoke the Date object's toString() and put the date string directly in the HTML.
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Note: Eclipse may automatically import Util.Date at the top of the jsp:
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<%@page import="java.util.Date"%>
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This is a scriptlet tag:
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<% java code here %>
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A scriptlet lets you run java code inside it.
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An example of using a scriptlet:
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The scriptlet:
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<%
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Date today = new Date();
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String todayText = "Today is: " + today.toString();
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out.println("<ul><li>'out' is a JspWriter object.</li></ul>");
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%>
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Use variable that is inside the scriptlet:
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<p>This paragraph is outside the scriptlet but we can use stuff from inside the scriptlet:</p>
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<ul>
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<li><%= todayText %></li>
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</ul>
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Note: In Eclipse use ctrl+space to show pre-defined variables of a scriptlet.
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Run your .jsp file
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VIDEO #5 Notes:
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Understanding the web.xml file.
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When creating a new Dynamic Web Project there is a choice to "Generate Web.xml deployment descriptor".
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John suggests creating this because the annotation in the servlet, @WebServlet("/Video_3_servlet"),
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may not be recognized by some server applications. So he prefers to use the Web.xml file. Additionally,
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later on we'll have a need to manipulate the web.xml file.
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*** Instead of making a new project I chose to google how to add a Web.xml if my project doesn't contain one:
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source:
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http://crunchify.com/eclipse-missing-web-xml-file-how-can-i-create-web-xml-in-eclipse/
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Procedure:
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R-click project --> Java EE Tools --> Generate Deployment Descriptor Stub
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This creates "web.xml" file in WEB-INF
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I created the following for this video:
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* Video_5_servlet.java
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* index.jsp
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* myLoginPage.jsp
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[ ] Video_5_servlet.java
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After creating this file look at the line immediately above the class declaration and you'll
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see the following:
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@WebServlet("/Video_5_servlet")
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Comment that out:
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//@WebServlet("/Video_5_servlet")
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We don't want that active. Commenting that out will give a warning that there's an import that isn't
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used, ctrl-shft-o to organize imports.
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If we run this servlet now we'll get a 404 HTTP status error: The requested resource is not available.
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This is because we now need to add a reference to this servlet into the web.xml file.
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[ ] web.xml
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Located in WebContent/WEB-INF/web.xml
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Map a URL address to my servlet:
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In web.xml create <servlet> & <servlet-mapping> tags for the Video_5_servlet
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located in the "gui" package:
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<servlet>
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<description></description>
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<display-name>NameSeenInAnAdminTool_Maybe</display-name>
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<servlet-name>kitten</servlet-name>
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<servlet-class>gui.Video_5_servlet</servlet-class>
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</servlet>
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<servlet-mapping>
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<servlet-name>kitten</servlet-name>
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<url-pattern>/one</url-pattern>
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</servlet-mapping>
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Names given to <url-pattern> can basically be whatever you want, but whatever name you give
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here is the URL address that points to this servlet.
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The <servlet-name> can also be whatever you want, as long as it is unique in the web.xml file.
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All it does is link the <servlet> and <servlet-mapping> tags, so the program knows what goes
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with what.
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[ ] Video_5_servlet.java
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Now run this servlet.
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Notice the address bar in the browser:
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http://localhost:8080/JSP_Tutorial_1/one
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Now if you type this into the address bar:
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http://localhost:8080/JSP_Tutorial_1/Video_5_servlet
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...it won't work, the 404 "The requested resource is not available." is reported.
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So now, as far as the server is concerned, the URL address for the Video_5_servlet is
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http://localhost:8080/JSP_Tutorial_1/one
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[ ] myLoginPage.jsp
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Very simple .jsp.
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Make a web.xml entry for this page:
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<servlet>
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<description></description>
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<display-name></display-name>
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<servlet-name>MyLoginPage</servlet-name>
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<jsp-file>/myLoginPage.jsp</jsp-file>
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</servlet>
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<servlet-mapping>
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<servlet-name>MyLoginPage</servlet-name>
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<url-pattern>/two</url-pattern>
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</servlet-mapping>
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Two things to note:
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1) in the <servlet> tag it isn't a <servlet-class> but rather a <jsp-file>, and
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it requires the ".jsp" extension.
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2) URL address for this page is: http://localhost:8080/JSP_Tutorial_1/two
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[ ] index.jsp
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R-click WebContent --> New --> JSP File --> name it.
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This was created to demonstrate that if you have one of these files then a address that
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only has the context root will go here:
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This:
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http://localhost:8080/JSP_Tutorial_1/
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Goes to the index.jsp.
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Why? Because in the web.xml there is a welcome file list:
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<welcome-file-list>
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<welcome-file>index.html</welcome-file>
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<welcome-file>index.htm</welcome-file>
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<welcome-file>index.jsp</welcome-file>
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<welcome-file>default.html</welcome-file>
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<welcome-file>default.htm</welcome-file>
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<welcome-file>default.jsp</welcome-file>
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</welcome-file-list>
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...and index.jsp is on it. (this list was automatically created and represents popular names
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for HTML pages that "direct" users to other pages within the web site.
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Run the context root:
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R-click the project folder, JSP_Tutorial_1, --> Run As --> Run On Server
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Doing that will make a call to the Tomcat server using only the context root for the URL.
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NOTE: There's a small summary section on this topic in JSP_Tutorial_8's notes, right at the top.
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VIDEO #6 Notes:
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Deploying the servlet to my local Tomcat server.
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...which isn't much different than what Eclipse was doing, says John, but it is good for debugging.
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A WAR file is like a .jar file for deploying onto a server application (like Tomcat).
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Export program as a WAR file:
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- R-click project --> export --> WAR file --> save somewhere.
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- Paste WAR file into Tomcat 7.0/webapps
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- Stop Eclipse version of Tomcat.
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- Start Tomcat service: use "Monitor Tomcat" program to do that.
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- Open browser and type into address bar:
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Address: Result
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server: http://localhost:8080 TomCat web page
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context root: http://localhost:8080/JSP_Tutorial_1 contents of index.jsp
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Video_5_servlet.java: http://localhost:8080/JSP_Tutorial_1/one what was written in the doGet() method
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myLoginPage.jsp: http://localhost:8080/JSP_Tutorial_1/two contents of MyLoginPage.jsp
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Context root is probably the name of your project (though you could have changed that when
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you first constructed the project using the wizard).
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NOTE: when you paste your WAR file into TomCat's webapps folder and then run Tomcat, Tomcat then makes
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a folder named the same thing as your WAR file. So if you want to delete the WAR file then also delete
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the folder generated by Tomcat that has the same name as the WAR file.
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VIDEO #7 Notes:
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I used Cloudbees, like the video. I researched using other sites for hosting java applications but I ran into
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a world I know very little about and the jargon threw me for a bit of a loop.
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Cloudbees notes:
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After having set up an account,
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Applications --> click "Add Application" tab at the top --> name it, Cloudbees builds a shell or something
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for an application --> look for the label mid-page that says "Upload Application" --> click "Choose File"
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--> select your WAR file --> and that's about it.
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Click your hyperlink to your website found near hte top of the page --> your website opens in a new
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browser --> try appending some of the url-names given to your files in web.xml into the browser.
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*** Admire that you have uploaded to the world wide internety thingymajig an application/website that you
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have created. And it works!
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- Now celebrate.
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THE END of JSP_Tutorial_1.

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