Readings:

• Chapter 3 in Parsons book
• Read Sections 4, 5, and 6 in IETF RFC 2616 (http://www.ietf.org/rfc/rfc2616.txt) which is the one that defines HTTP 1.1 to get a more detailed idea of how HTTP works and what RFC's contain in general. It's good to know where to find these technical documents and how they are structured when you need details on how things work on the Internet and the web.

Tasks:

In this assignment we are going to examine how a VERY simple HTTP server with the capability for running pre-compiled Java Servlets (Java server-side programs that can be used to produce dynamically generated content) works. This server is extremely simplistic, but it is able to respond to HTTP GET requests for any static HTML files found in its '/webroot' directory as well as being able to run any Java Servlets which have been compiled into classes and placed in that same location. This is the essence of a Web Server/Servlet Container application such as Apache Tomcat.

1. First, before starting up NetBeans, please make sure you can find the project directory on your machine where NetBeans holds all your NetBeans project files. On my Linux system this is called NetBeansProjects in my home directory (on a Windows system this is most likely somewhere under "C:\Documents and Settings\xxx'" where 'xxx' is your Windows username). When you create new projects (using 'File->New Project' on the main NetBeans menu or by hitting Ctrl+Shift-N, for example) this is the directory shown as the 'Project Location:' when filling in the project details on the 'New Project' panels. This is also the directory where your HelloWorld project from Assignment #1 should be found.

2. Once you've located this directory, download the simple HTTP Server and Servlet Container project compressed ZIP file to your system and place the .zip file in your NetBeans project directory as described in Step 1.

3. Unzip the HowWebServersWork.zip file right into this same directory. It will create a full HowWebServersWork project directory structure in your main project folder. You can use Winzip (www.winzip.com) or any other ZIP program of your choice to decompress the zipped file.

4. Now, start up NetBeans as usual.

5. Go to 'File->Open Project' or use Ctrl+Shift-O to open the now unzipped project in NetBeans. Make sure you are looking in the correct directory, again in my case that is NetBeansProjects. You should see the project labeled HowWebServersWork in your projects directory.

6. Click on HowWebServersWork to select the project and hit the 'Open Project' button. You should see the web server project in the 'Projects' panel in the upper-left corner of the NetBeans window.

7. Double-click on the project's name and it will open to show you all the source files, libraries (servlet.jar and the JDK), and folders containing any test files (there are no test files in this project). The HTML files and compiled Servlet class files we'll be working with are in the project's "webroot" directory.

8. Keep double-clicking on the Source Packages till you see the .java files in the HowWebServersWork package. Read through all of the .java files in the project to get a feel of how this simple HTTP server handles requests and responses, and what a trivial Java Servlet looks like.

9. Now we're ready to run our toy HTTP Server/Servlet Container, which can both GET files and execute pre-compiled Java Servlets. NOTE: Both .html files and compiled Java Servlet .class files must be located in the project's "webroot" directory for this server to find them properly. On my system this directory is called, NetBeansProjects/HowWebServersWork/webroot.

10. You'll find several .html files (including 'index.html', which is the default file retrieved when the URL you input to your browser is simply 'http:/localhost:XXXX/' --- [Note: 'XXXX' is the port number that your HTTP server is listening on for HTTP Requests.] Any HTML files you place in the "webroot" directory can be served up by your simple server.

    NOTE: You'll have to find the port # the web server is currently using by reading through the .java files carefully in the project. You'll also find a few .class files in that same 'webroot' directory, which are compiled Java Servlets. These .class files are ready to be executed by our simple web server. One servlet is not called directly by the user (that's ErrorServlet which informs the user about servlet errors), but the other, PoeticServlet, can be requested as part of a URL. More on that a little later however.

11. Since this project has already been built (normally you'd do 'Build Main Project' (F11) to compile and link everything before it is runnable), you only need to execute 'Run Main Project' (or use F6 or click on the right green-arrow icon on the main toolbar or the double green-arrow icon left of the 'Output' panel at the bottom of the NetBeans window) to get the HTTP server running on your system. Once running, the server can be stopped by hitting the small red button icon to the left of the Output panel.

12. Now run the HTTP server main program, SimpleWebServer, as described in the previous step. In the Output panel at the bottom of the window you will see:

    init:
deps-jar:
compile:
run:
Simple HTTP Server listening for requests...

    and the double green-arrow next to the text will now be grayed-out with the red 'stop running' icon directly below it now activated. You can click on this icon to halt the running program.




13. Open your Firefox browser and from the main 'Tools' menu, select the 'Live HTTP headers' add-on you'd previously installed. This will open a separate 'Live HTTP headers' window. Keep this window open and watch the HTTP conversation in the background as you do the rest of this exercise. This add-on will automatically capture all the HTTP communications from this point on till you save it away as a file that you will submit as part of the assignment later on. You may be surprised by exactly what is being transmitted and received by your browser depending on what else it happens to be doing at the time.

14. In your browser's address (URL) input area enter 'http://localhost:XXXX/' (remember 'XXXX' is the port number that the server is using for incoming requests). At this point you will see the default 'index.html' page used by our example web site. Capture what it says with a screenshot of the browser's window and submit that image file as part of Assignment #2. Most OS's can make use of the "PrtSc" (Print Screen) key on your keyboard to capture an image of the screen. Alternatively, you can add the Firefox Screengrab! add-on to your Firefox browser. This can be used to capture any output shown in the browser window.

15. Now try entering a nonexistant URL, e.g., 'foo.html' (that is, one not in the 'webroot' directory). Take note of the HTTP response in the Live HTTP headers window.

16. Now run the servlet named, PoeticServlet, using the convention that all our servlets are accessed using an URL that looks like the following:
    
    http://localhost:XXXX/servlets/YYYYYYYY
    
    where 'YYYYYYYY' is the name of the servlet. Take a screenshot of the page generated by the servlet. You should upload this image file to Assignment #2 when you are done.

17. Before leaving this servlet's dynamically generated page, use the Web Developer Firefox add-on you installed to view the page's generated source. From the main Firefox 'Tools' menu select 'Web Developer->View Source->View Generated Source' to see exactly what the servlet generated compared to what is in the .java file in the project directory. The Web Developer toolbar should also be visible right above the main browser window and can also be used to get to the same functionality. If the toolbar's not visible, use 'View->Toolbars->Web Developer Toolbar' to expose it. When the Web Developer window with the generated source appears, save it to a file using 'File->Save Page As...' and submit that file as part of Assignment #2.

18. You can also pass a special parameter as part of the URL to tell this server to shut itself down. You need to read through the source code carefully to find the magic word which shuts down the server. When you're ready to quit, enter the following URL into the browser's address input area, "http://localhost:XXXX/magicword", where "magicword" is the special shutdown command you discovered in the source files. Check the NetBeans Output panel and you'll see that the server has indeed terminated. Right-click on the NetBeans Output panel and use "Save as..." to save the entire console output for your web server into an external file. Submit this file as part of Assignment #2.

19. Lastly, in the Live HTTP header window, which has been capturing all the HTTP conversations between your browser and the servers it has communicated with, click on the 'Save All...' button to save the log as an external file. Read over this file to get a better feel for the conversation between a browser and a server and then upload it and all the other output files for Assignment #2 mentioned previously to the class FTP server, placing them in the assignment-2 subdirectory.

Readings:

• Review Chapter 3 in the Parsons book again to refresh your understanding of HTML concepts.
• You can refer to the on-line HTML/XHTML reference found here as needed.
• A brief reference card containing all the core HTML concepts in one spot can also be found here.
• Many HTML samples can be found in the 'Other Resources' section of the class web server

Tasks:

• Here are the contents of a browser window that is displaying a single, simple HTML page (i.e., it contains no CSS styling) after it has loaded, but BEFORE the user has interacted with it. Recreate this page using HTML (strict XHTML 1.0 syntax, please), making it look as identical as you can (in every respect, including all the notes you see in the example verbatim) to the screenshot of the browser window you were given. Don't worry if the fonts or the absolute sizes of the text are not exactly the same. Those are browser and user dependent. The relative sizes and placement on the page should be pretty close however. Also, all the hyperlinks and the "Back to class" button should really work. The URI's they're attached to are shown in the PDF example itself.

  You can use any editor you choose that can output plain text files (e.g., Notepad, vi, emacs, MS Word, etc.) to write your HTML. Here is a basic XHTML template you can copy to help you get you started. However, for most students it's suggested that you use the HTML editor built into NetBeans which provides a lot of nice editing features for writing HTML. Just start up NetBeans and then do "File->New File...->Other->XHTML File" to create a new HTML file which uses the XHTML 1.0 Strict DTD. If it's not already showing, make sure you do "Window->Palette" in NetBeans to display the HTML tools widgets. You can drag-and-drop these into your HTML page as needed. This HTML file is the one that you'll load into Firefox using 'File->Open File' to display the page you have created.

• While you are in the process of writing your page, you should revalidate the HTML in the file as you go using the Firefox Web Developer add-on to make sure it continues to adhere to the XHTML 1.0 strict DTD. From the Web Developer toolbar in Firefox select 'Tools->Validate Local HTML' after you've loaded the latest version of your page into Firefox. Don't forget to reload/refresh the browser page after each set of edits you make to see all the changes added since the last save. Then revalidate. You can also upload your local file by hand to the W3C Markup Validation Service.

  Whichever method you use, your HTML file MUST validate cleanly and completely before uploading the functioning HTML file to the class FTP server under assignment #4. If it doesn't, please edit it again and revalidate it.

  NOTE: Remember that since the DOCTYPE DTD in the template specifies 'strict' XHTML 1.0, the case for all elements must be lower case and every tag must have either a separate terminating tag or be self-terminating as in: <img src="/images/unh-logo-2.gif" alt="UNH Dept. of Electrical & Computer Engineering and Computer Science" />. Pay attention to the "space/" before the closing > in the tag. If you don't do this, then the HTML Validator will flag them as errors.

Readings:

• Review Chapter 10 in Parsons book to refresh your understanding of servlets, JSP, etc. for this week's tasks shown below.


• Go to Sun's J2EE Core Patterns page and read the detailed information on (i.e., click on the diagram in the appropriate spot) each of the following Java EE architectural patterns: Front Controller, View Helper, Dispatcher View, Transfer Object and Data Access Object. We've been discussing these ideas as part of explaining the overall MVC JSP Model 2 concept. You will be using some combination of these patterns in the MVC-based design for your Term Project to separate the Model from the View from the Controller components in your final application.

Tasks:

1. Review all your previous assignments, the readings in the textbook and the other online readings you done thus far, and your lecture notes. The midterm exam will be given during the next session covering everything through the end of Session #6. It will be open book (no electronic devices, please) and should last about 1/2 of the class.


2. Download the Chapter 10 examples which accompany the Parson's book from this location. These are the sources for the examples and diagrams that you see in Chapter 10. You can certainly download and examine any of the other examples as well, but focus on Chapter 10 to make sure you're comfortable with the basics of Servlets, JSP, and MVC.


3. Unzip the downloaded Chapter 10 examples file into to your NetBeans project directory and start NetBeans. I've converted all these examples into Netbeans projects so you should be able to load them from inside of NetBeans ("File -> Open Project"). You will find the examples inside of the "Chapter 10" folder in your NetBeans directory.


4. Open each project in turn, build it, and run it as a Tomcat application (F11 and F6). The running applications should appear in your browser using the URI starting with "http://localhost:8084/" (Note: the port might appear as 8080, depending on how you installed NetBeans). Once you understand how each app acts within the browser, go back to NetBeans and examine the HTML, JSP, and Java sources closely inside the project to see how these components work together. Please go over each one slowly and carefully to make sure you understand as much as possible how the incoming HTTP requests are handled, the webflows are managed, and the responses are being generated. Don't worry if you don't understand ALL the syntax of JSP's and JSTL yet, we'll be covering the details in class. Send me any queries, if you're confused.


5. Do Exercise 10.1 ('AcceptLanguageServlet') in the Parsons' textbook. Refer to the online Javadocs for details on all the classes and methods supported by the Java API's. Focus particularly on javax.servlet.http and javax.servlet.jsp for information on handling requests and responses using servlets and JSP's.