The request-response cycle is the method by which web applications retrieve data from sources on the web. The client sends a request to a server that will use the data in the request to return a response. When the client performs some other action, it sends another response and the cycle continues.
2. Explain how servlets facilitate processing of the request-response cycle.
A servlet is a program that runs on the server to handle requests and return responses to the client. Unlike client applets that run on the client side and send requests, a servlet receives requests from the client, performs some operations, and returns a response.
3. How do you login to the Tomcat Manager?
To login to Tomcat Manager you simply run Tomcat on your local machine and connect to http://localhost:8080/ and click on the "Tomcat Manager" link. You are then prompted for the username and password that is defined in the conf/tomcat-users.xml file.
4. What is the Tomcat Manager used for in the StackStripes application?
The Tomcat Manager enables you to make the StackStripes program available to web users. The StackStripes application provides the Tomcat Manager with locations and configuration options of files that are to be deployed on the server and the manager makes them accessible to clients.
Any application that is deployed on Tomcat and therefore available to web users is contained in the webapps directory. Within the webapps directory, each application will have its own directory structure. The StackStripes application has, within its folder in the webapps directory, the following files/folders:
5. What is the directory and file layout of an installed web application like StackStripes? (This is NOT the same as the directory and file layout of the StackStripes distribution!)
META-INF - Contains meta file(s) with various meta data about the application.
WEB-INF - Contains the actual application and configuration files.
index.jsp - The default page that loads when no specific file is provided.
6. How do you build a war directory structure in Ant? Where is this accomplished in the StackStripes application?
A war directory structure can be built using ANT with a build.xml file. The build.xml file for the StackStripes creates a war structure in the "war" target. It contains a war element that creates a .war file in a specific file location defined within the element.
7. How do you install a war directory in a running Tomcat server? What information does the Ant task need to accomplish this?
If configured to automatically deploy, you can simply place a war directory into the webapps folder to install it on the server. The Ant task needs only to know the location of the webapps folder which is available in the $CATALINA_HOME environment variable.
8. What is the "Model2" architecture? What are its advantages?
Model2 is also knows as MVC (or Model View Controller) because it structures the client/server architecture into three components. The model contains any data or structures needed to maintain it (ie. database), the view contains the client presentation, and the controller accepts requests from the client and gives necessary data to the model. This architecture provides modularity and allows each component to be built in such a way that changes to one will not impact the others.
9. What are JSP pages? How are they related to servlets?
JSP (or JavaServer pages) are pages that are compiled into Java servlets on the server. They allow the server to dynamically generate pages in response to a client request.
10. Why is there a delay when retrieving a JSP page for the first time? Where is the Java code for that page stored?
Since they must be compiled into a servlet the first time the page is being retrieved, there is a delay for the JSP compiler to run on the server. However, once the servlet is compiled it is contained within memory and does not need to be compiled for further use.
11. What are JSTL tags? Why are they useful? What is an example JSTL tag from the StackStripes system?
JSTL tags are a set of tags usable within JSP pages provide methods for performing common tasks without the need of embedded Java. Since they allow you to perform tasks without embedded Java, they allow better separation of the application from the user interface defined in the JSP pages. The StackStripes system uses "c:forEach" tag to easily iterate and display all of the elements of the stack.
12. What are Stripes tags? Why are they useful? What is an example Stripes tag from the StackStripes system?
Stripes tags are tags defined by the Stripes web application framework. They enable you to easily link JSP tags with classes and methods in the Java application. Many Stripes tags are needed by the StackStripes system, for example the tag
< stripes:submit value="push" name="push"/>
causes the method called push to be evoked when the user clicks the "push" button.
13. What is HttpUnit? How is it different from JUnit? Why is it useful? What is an example use of HttpUnit from the StackStripes system?
HttpUnit provides a method for visiting and performing operation on websites automatically within code. It allows us to test systems that operate on the web, while JUnit is limited to a single local system. Every test that is performed on the server requires HttpUnit to run. Every test of the JavaActionBean class of the StackStripes uses HttpUnit.
14. What needed to be changed in order to implement the Double It button? What didn't need to be changed? What did you learn about the MVC design pattern from this exercise?
Very little had to be changed to implement the DoubleIt button. I simply had to add a new form to the JSP page and add the functionality to the StackModel class. The controller component did not have to be changed. This exercise illustrated how the MVC architecture allowed functionality to be added without changing every component.
15. What are the equivalence classes that need to be tested for the Double It button?
There were only two equivalence classes that needed to be tested: doubling an empty stack and doubling a non-empty stack.
16. Provide two screen images of your new StackStripes application with the Double It button, one showing the page before and one showing the page after hitting the "Double It" button.
And after clicking the "Double It" button.
17. What is the singleton design pattern? What is an example of its use in StackStripes? Why is it needed?
The singleton design pattern restricts the class to having only a single instantiation. For all users to interact with the same stack, this method is required. The stack in the StackStripes system is defined as a singleton by declaring the constructor as private and defining a single instance variable was static.
18. Some of the StackStripes tests exercise code on the "server side", while others exercise code on the "client" side. Which test classes exercise code on the "server", and which exercise code on the "client"? How does Emma deal with this to create appropriate coverage data?
The tests in TestStackActionBean are run on the server while the tests in TestStackModel run on the client. Emma can collect coverage data from both classes of JUnit test cases, but it cannot collect the data on the server until Tomcat is shutdown. That is why the emma.build.xml file shuts down the Tomcat server.
19. Running 'ant -f junit.build.xml' results in the following target invocations: tomcat.check, tomcat.undeploy, compile, war, tomcat.deploy, junit.tool, junit.report, junit. Explain what each of these targets do.
tomcat.check - checks to make sure Tomcat is currently running on the local machine and that it has the correct login/password.
tomcat.undeploy - deletes StackStripes from the Tomcat server.
compile – compiles the StackStripes system.
war – builds the war directory structure to be deployed on the Tomcat server.
tomcat.deploy – deploys the previously created war file to the Tomcat server.
junit.tool – runs all JUnit tests.
junit.report – creates the JUnit report files.
junit – Runs both the junit.tool and junit.report targets.
No comments:
Post a Comment