Passed SCJD.

[mayuresh chaubal]

Hi All,
Finally passed the exam.
It took me whole year to complete the assignment.[4-5 dedicated months are enough. It took me long because of my professional duties.]

Here is the score.

General Considerations (maximum = 100): 92
Documentation (maximum = 70): 70
O-O Design (maximum = 30): 30
GUI (maximum = 40): 40
Locking (maximum = 80): 80
Data store (maximum = 40): 40
Network server (maximum = 40): 40
----------------------------------------------------------
Total 392/400

I also recieved an appreciation regarding my locking mechanism.

This site has helped me a lot during the build and submission. [I did not read any other book. I think this site has enough help.]

Thanks.

-
Mayuresh

[Vasya Pupkin]

Splendid!!! congratulations!
can you please answer these questions too?
Thanks.

[mayuresh chaubal]

I can answer 2 of your questions.

3) why did you choose to have a separate business layer? what functionality did you put in there?
Separate business layer encapsulated operations in my data class.
the data class was never shown to client, all client could see was a business interface.
here is the business interface [or server interface]

/**
 * Interface for sending requests to database.
 * <p>
 * <b>Data manipulation Requests:</b><br>
 * These requests are used to see current state of data. Also to modify the data
 * state if needed. Requests like readRecords, readAllRecords, findRecords,
 * updateRecord, createRecord, deleteRecord are data manipulation requests.
 * </p>
 * <p>
 * <b>Metadata Request:</b><br>
 * Request getDataFormat is intended to return metadata information about
 * database file. This information is used in building user interface.
 * </p>
 * @author mayuresh
 * 
 */
public interface RequestHandler extends Remote {
	/**
	 * Fetches the valid records whose record number is given in input array.
	 * Validity of records is described in file format of the database file.
	 * 
	 * @param recordNumbers
	 * @return array of records.
	 * @throws RemoteException
	 * @throws RecordNotFoundException
	 */
	public String[][] readRecords(int[] recordNumbers) throws RemoteException,
			RecordNotFoundException;

	/**
	 * Fetches all the valid records in database file. Validity of records is
	 * described in file format of the database file.
	 * 
	 * @return array of records
	 * @throws RemoteException
	 * @throws RecordNotFoundException
	 */
	public String[][] readAllRecords() throws RemoteException,
			RecordNotFoundException;

	/**
	 * Returns array of record numbers whose fields match the input criteria.
	 * Matching algorithm is implementation specific. Only returns the records
	 * which are valid. Validity of records is described in file format of the
	 * database file.
	 * 
	 * @param matchingFields
	 * @return array of record numbers
	 */
	public int[] findRecords(String[] matchingFields) throws RemoteException;

	/**
	 * Deletes the records whose number matches the one provided in input.
	 * Consistency of the candidate record is checked before it is deleted.
	 * Deletion is achieved by invalidating the record in database file. Throws
	 * ReecordNotFound exception if record corresponding to given number is not
	 * found
	 * 
	 * @param recordNumber
	 * @throws RemoteException
	 * @throws SecurityException
	 * @throws RecordNotFoundException
	 */
	public void deleteRecord(int recordNumber,String[] currentRecord) throws RemoteException,
			SecurityException, RecordNotFoundException;

	/**
	 * Updates the record with new values. The update procedure first checks if
	 * records at client and server are in sync. If found not in sync, the
	 * method throws SecurityException. Otherwise updates the record.
	 * 
	 * @param recordNumber
	 * @param newValues
	 * @param oldvalues
	 * @throws RemoteException
	 * @throws SecurityException
	 * @throws RecordNotFoundException
	 */
	public void updateRecord(int recordNumber, String[] newValues,
			String[] oldvalues) throws RemoteException, SecurityException,
			RecordNotFoundException, UpdateRecordException;

	/**
	 * Creates new record in database file. The creation procedure checks for
	 * invalidated records. If found, updates it with new record values and
	 * makes the record valid. If no invalid record is found, a new entry is
	 * added at the end of the file.
	 * 
	 * @param recordValues
	 * @throws RemoteException
	 * @throws SecurityException
	 * @return Record number of newly created record.
	 * @throws RecordNotFoundException
	 */
	public int createNewRecord(String[] recordValues) throws RemoteException,
			SecurityException, DuplicateKeyException;

	/**
	 * Returns database meta data object for database file.
	 * 
	 * @return metadata object for provided database file.
	 * @throws RemoteException
	 */
	public DBSchema getDataFormat() throws RemoteException;

	/**
	 * Closes all underlying connections associated with this object.
	 * 
	 * @throws IOException
	 */
	public void close() throws IOException;

i hope things can be clearer by looking at this. do reply in case of doubts.

4) how does your gui look like? Did you implement observer pattern?
my gui code was mvc.
a table model encaplsulated my data class.
there was a listener for every type of action. ie Search, Update, Add, Delete.
I used a singleton facade class to access all the current variable set in client.
ie
Client.getInstance().getUIManager().get...
and Client.getInstance().getUIManager().set...

[Vasya Pupkin]

I do use a separate interface to expose the data instances to the clients too. I would never call it "business layer".

4) it is kind of obvious what to code in gui part. I was curious about how the gui looks like. Where did you place your buttons, table, fields? Did you use a context menu? Did you allow sorting, moving columns? Did you use filtering? and so on

Thank you very much for the explanation.

[mayuresh chaubal]

gui had following components.

a menubar containing all the global functions with shortcuts.
a table in the middle. a popup menu for the table [Book/unBook Room]
searchpanel at the bottom.
the panel contained 2 labeled editable comboboxes.
1. to search hotel names
2. to search city names.
above to comboboxes suggested current hotel names and city names.

the panel also had a checkbox saying "show the rooms in avaiable in 48 next hours only."

each one of the above components was provided with search action listener. thus any action here would result in change in table rows.
there was no search button.

rest of the functions resided in menubar.
the functions were Create Record, Delete Record, BooK/UnBook Record [Redundant], Settings, About etc.

at the very bottom there was status bar. it dispayed status of previous action ie "Succeeded/Failed" with additional description

apart from this main window. there were extensions of dialog boxes which helped specify properties.
eg "Add new Record Dialog" or "Settings Dialog"

all the ui components refered global variables [as described in previous post].

let me know if you require more.

[Roel De Nijs]

Congratulations with your great score

mayuresh chaubal wrote:I also recieved an appreciation regarding my locking mechanism.

What was so special about your locking mechanism?

[mayuresh chaubal]

thanks roel.

and congratulations to you too.

regarding the locking.

there was Registry which held record numbers of currently locked records.
when new recordnumber was added to registry, a new lock was created and assigned to record number.
if the recordnumber was already present in registry, the thread would wait on lock assigned to the record number.
when the lock was removed. waiting thread would create new lock.