Skip to main content.

Lab 4: Servlet Configuration and Session State

Goals

At the completion of this lab, you should be able to

Set up

Create a new Dynamic Web Project called Lab4.

Adding init and destroy Methods (45 pts)

Copy pet.html and SurveyServlet.java from their current location to the Lab4 project.

SurveyServlet is not implemented very efficiently. The file has to be read and written every time a vote is cast, i.e., every time a request comes in. We don't want that overhead because we expect this survey to be taken a lot! (Not really but...)

Add init and destroy methods to SurveyServlet. init will read the file and initialize the votes. destroy will write the votes out to the file. More detailed instructions follow:

  1. First, recall that you can use the "Refactor" and "Source" menus of Eclipse to quickly do trivial tasks.
  2. In the SurveyServlet.java editor pane, right-click, select "Source", select "Override/Implement Methods".
  3. In the GenericServlet class select init and destroy, select where to put them (I put them below the constructor), and then click "OK". These method stubs will be automatically generated for you.
  4. Move the variables surveyData, votesForAnimals, and totalVotes so that they are instance variables for the class rather than temporary variables for the doGet method.
  5. Move the code that reads in the file into the init method. Call super.init() first. You will have to handle some compiler errors appropriately.
  6. Move the code that writes the file into the destroy method. Call super.destroy() last. You will have to handle some compiler errors appropriately.
  7. Stop and restart your server.
  8. Test your servlet several times.
  9. Stop and restart your server.
  10. Test again. Still works, right? Good!

Web Application Structure and Deployment

build Directory

Within a terminal (not within Eclipse), look at the contents of the build directory inside of your FirstServlets project. You should see the .class files for each of your servlets. The build directory and the contents of the WebContent directory are what are deployed on the server.

Configuration Parameters (30 pts)

Sometimes, you want to be able to easily configure your servlets. For example, you want want to tell the servlet the location of a file or the parameters to a database or the email address of the administrator.

  1. Modify the SurveyServlet to include an init parameter. The init parameter's name is surveyFile and the value is survey.dat.

    You can modify the web.xml file or add the annotations to SurveyServlet. To see examples of annotations, look at the slides or use Eclipse to create a new servlet and generate an example annotation for you.

  2. Modify SurveyServlet's init method to access the init parameter. (Look at the methods that SurveyServlet inherits from HttpServlet).
  3. Stop and restart the server.
  4. Test that the code still works correctly.
  5. Stop the server. Modify the parameter so that the SurveyServlet's init parameter has a different file name, such as survey2.dat.
  6. Restart the server and test your code. You should not get the data you had before: it should be all 0s, except for whatever you just voted for.

Using Sessions and Session Variables (25 pts)

Copy your Login servlet and form from Lab 3 into this project. (Remember the appropriate locations for both of these files.)

Modify your Login servlet so that, if the user's name and password are correct, it starts a new HttpSession and stores an attribute with name authenticated and value a Boolean object that has a true value. (Note that this must be a Boolean object and not a boolean.)

Also set your session's maximum inactive interval to 60 seconds.

To test that your servlet is working correctly:

  1. Copy this form and this image into your WebContent directory
  2. Create a new servlet in the servlets package named AuthenticatedTest
  3. Copy this code into the doGet method of the servlet you just created (AuthenticatedTest). Look at the code to understand what it is supposed to do.
  4. Restart your server.
  5. Try clicking the button of the authenticate test form. You should see a message that says that you're not authenticated.
  6. Login, using your login form copied from last lab.
  7. Try clicking the button of the authenticate test form again. You should now see a message that you are authenticated.
  8. Wait 60 seconds and test the authenticate test form again. You should no longer be authenticated because the session expired.

Organization

Create an index page that links to the pet survey, the login page, and the authentication page.

Turnin

Create a .war file from your Lab4 project and copy it into your turnin directory. Make sure to include the source code.

Grading (100 pts)