Thursday, March 24, 2011

Self Test: Chapters 20 to 24

Questions

Question 1:
Which of the following two methods are used to track or store the session ID?
A. encodeURL()
B. sessionTrack()
C. sessionUpdate()
D. encodeRedirectURL()

Question 2:
How do you create a session?
A. createSession()
B. makeSession()
C. callSession()
D. getSession()

Question 3:
How do you retrieve a session object across multiple requests to the same or different servlets within the same WebApp?
A. retrieveSession()
B. findSession()
C. getSession()
D. callSession()

Question 4:
How do you store objects into a session object?
A. put(String, Object)
B. setAttribute(String, Object)
C. addObject(Object)
D. putObject(String, Object)

Question 5:
How do you know if a session is alive?
A. Look in the cookies.
B. getSession(false)
C. isSessionAlive()
D. Exception thrown if you try to create one when one already exists.

Question 6:
How do you destroy or expunge a session?
A. Session.isAlive = false;
B. Session.isNew(false)
C. invalidate()
D. removeSession()

Question 7:
How do you know when a particular object is added to a session?
A. getCreationTime()
B. getAttribute(Date)
C. Session.attributeDate(index)
D. attributeAdded(HttpSessionBindingEvent)

Question 8:
How do you know when a session is created?
A. sessionDidActivate(HttpSessionEvent)
B. You check with sessionIsAlive().
C. You only know when it is killed.
D. When the SESSIONID becomes null.


Question 9:
How do you know when a session is destroyed?
A. sessionBound(HttpSessionEvent)
B. sessionFinalize(HttpSessionEvent)
C. sessionWillPassivate(HttpSessionEvent)
D. valueBound(HttpSessionEvent)

Question 10:
Given that URL-rewriting must be used for session management, identify the query string attribute used when URL-rewriting.
A. sessionid
B. servletid
C. jsessionid
D. containerid

Question 11:
Where are cookies stored?
A. On the server.
B. In web.xml.
C. On the client.
D. In HTML.


Question 12:
Where are session IDs stored?
A. In cookies.
B. In HTML form fields.
C. In query strings.
D. Session IDs are not stored.

Question 13:
Which two technique can be used by a Web container to manage session IDs?
A. deleteAttribute(String)
B. attributeRemove(String)
C. removeAttribute(String)
D. setAttribute(null)

Question 14:
How do you get the date stamp of the session's creation?
A. getCreationTime()
B. sessionDate()
C. getSession(Date)
D. From the response object.

Answers:

Answer 1: A and D. You append the session ID in URLs by calling the response's encodeURL(URL) (or encodeRedirectURL()) method on all URLs returned by a servlet. This method includes the session ID in the URL only if cookies are disabled; otherwise, it returns the URL unchanged.

Answer 2: D. To get the current session in a servlet, you call the getSession() method of HttpServletRequest. You have one parameter to think about. If you don't provide a boolean, this method will create a session if one doesn't exist. The same behavior occurs when you provide a true boolean. However, the container will not create a new session if it doesn't already exist when you use a false argument.

Answer 3: C. This is the same question as #2, but stated differently. You call the getSession() method of HttpServletRequest to create a session.

Answer 4: B. You use the setAttribute(java.lang.String name, java.lang.Object value) method to add objects to a session. The other methods listed are incorrect.

Answer 5: B. This is somewhat difficult. You use getSession(false) method and test for a null result.
HttpSession session = request.getSession(false);
if (session = null) {
//do something about lacking a session
}

If you get a null then the session is alive. You can also check for the session ID with getId(), which returns the id of the session as a String representing the unique identifier assigned to this session. If the session is dead, it will return a null.

Answer 6: C. Only the invalidate() method can destroy a session. Notice that the session can't be referenced after this method has been called. A and D are incorrect and B isn't used properly.

Answer 7: D. The attributeAdded(HttpSessionBindingEvent se) method gets called as the notification that an attribute has been added to a session. The other options are incorrect.

Answer 8: A. The sessionDidActivate(HttpSessionEvent) method is called when the session has just been activated. The other options are incorrect.

Answer 9: C. The sessionWillPassivate(HttpSessionEvent) method is called as the notification that the session is about to be passivated. This is strange language so don't feel bad. They should have used another term such as alive or destroy. A and B are incorrect. D (valueBound(HttpSessionBindingEvent)) is the notification to the object that it is being bound to a session, but doesn't tell you about the session being destroyed.

Answer 10: C. The jsessionid is the parameter that is appended to URLs by the encodeURL() method when cookies are not available to maintain state. The other options are incorrect.

Answer 11: C. Cookies are stored on the client only.

Answer 12: A and C. Session IDs are stored in cookies on the client machine. If cookies are turned off, session IDs can be stored in query strings.

Answer 13: C. The removeAttribute(java.lang.String name) method removes an attribute. It deletes it from the session object. The other options are incorrect.

Answer 14: A. The getCreationTime() method returns a long containing the date stamp of creation. The other options are incorrect.

Previous Chapter: Quick Recap - Chapters 20 to 24

Next Chapter: Chapter 25 - Introduction to Servlet Exception Handling

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