NX SCJD: but passed with 155/155

[shan chen]

I just get test result. I took the new version assignment, but the grade was given as the old version. Thanks to all the helps I got from this forum! Follwoing is the detailed comments:

This report shows the total points that could have been awarded in each section and the actual number of points you were awarded. This is provided to give you per-section feedback on your strengths. The maximum possible number of points is 155; the minimum to pass is 124. Section Summary Report: General Considerations: Maximum=58 Deductions=0 Actual=58 Documentation: Maximum=20 Deductions=0 Actual=20 GUI: Maximum=24 Deductions=0 Actual=24 Server: Maximum=53 Deductions=0 Actual=53 Total: Maximum=155 Deductions=0 Certification Score=155

shan

[Lanuk Jajab]

Great job! a perfect score!

[Billy Tsai]

which new assignment did you do?
do you see the SCJD result directly after you login to the certmanager site?

[Max Habibi]

Nice Job! I'm moving this to the Cert results forum, so everyone can appreciate it.

M

[Francis Siu]

Wowwwwwwww..
Perfect

[Mark Spritzler]

Congrats Shan. Great job.
Mark

[shan chen]

Hi, Billy Tsai,

which new assignment did you do?

My assignment is URLyBird, hotel room booking project.

do you see the SCJD result directly after you login to the certmanager site?

Yes.
shan

[Ravi Arikere]

Congratulations!!!

[George Fung]

Congratulation.
Could you please share your desing pattern here? Do you use conncetion factory and lock manager?

[shan chen]

Hi, Grorge,

Could you please share your desing pattern here?

I would like to share my experience. In choices.txt, I indicated that I used three design patterns:
1. MVC
The pirpose is to separate the data display from the actual data representation. The view is implemented by the main window in ClientApplication.java, the controller is implemented by GUIController.java, the data model is implemented by String array, and the data access is implemented by DBMain.
The ClientApplication has a reference to GUIController, and GUIController has a reference to DBMain. Briefly, the structure is :
main window --> controller --> data model

2. Adapter
Adapter pattern is used to handle the problem that DBMain can not be bounded to the RMI registry.(There are many disscussions about this issue and my solution is just one of them).
I used an adapter RemoteDBAdapter to wrap DBMain. RemoteDBAdapter implementes RemoteDBMain. RemoteDBMain extends Remote. RemoteDBMain has all methods defined in DBMain , except each method throws RemoteException. In this way, RemoteDBAdapter can be bounded to RMI registry as the remote object.
At the client side, I used ClientDBAdapter as an adapter to wrap RemoteDBMain to DBMain. Thus, the data access class is always DBMain in both modes.
3. Factory
With the help of Adapter pattern, I defined method getDBAccess to create data access object of type DBMain for both network mode and non-network mode.
public static DBMain getDBAccess ( ) throws IOException {
if local mode:
return local data access;
if remote mode:
return remote data access;
}

Do you use conncetion factory and lock manager?

I used connection factory, as I explained in factory pattern.
No, I did not used lock manager.
Hope these are helpful.
shan

[Andrew Monkhouse]

Wow. Fantastic score. Congratulations.

[Maksim Golubkow]

Hi shan,
Congratulations, well done.
One question, have you data validation (such as owner id must be 8 digit number) in the methods updateRecord(...) and createRecord(...)?
Regards, Maksim

[George Fung]

Thanks your info. I will follow your design.. Congratulation

[shan chen]

Hi, Andrew,
You gave me many help too. Thanks a lot. Good luck to your test result!

Hi, Maksim,

have you data validation (such as owner id must be 8 digit number) in the methods updateRecord(...) and createRecord(...)?

Yes, I validated owner id to be an 8-digit number BEFORE it is passed as a parameter to any methods. I used WholeNumberField.java which extends JTextField to input owner id when booking a room. WholeNumberField uses PlainDocument to ensure the input is an 8-digit number.
Following are two threads about this topic:
https://coderanch.com/t/241875/java-programmer-SCJP/certification/set-maximum-input-length-JTextField
https://coderanch.com/t/183397/java-developer-SCJD/certification/NX-maximum-input-length-JTextField

Hope these are helpful.
shan

[Damian Ryan]

Well done, SCJD!

[Maksim Golubkow]

Hi shan, thanks for reply, but what i mean is following:

 public void updateRecord(String[] data) {
    check that data has the right length;
    check that evry value of data has the appropriate format;
 } 

Regards, Maksim

[shan chen]

Hi, Maksim,
Sorry that I have misunderstood your question. In my application, method update in Data.java does not check the parameter. My reason is: only the owner_id field is changed when method update is called to book a room (my JTable is not editable). As the owner id is guarrented to be an 8-digit number with the help of PlainDocument, method update does not have to check it again.
It is good to check data in method update, while in my personal opinion, I prefer to validate data on client side if possible.
Regards.
shan

[Maksim Golubkow]

Thanks shan, that helps me.
Regards, Maksim

[ChunChhau Liao]

Just perfect!!!
Congratulations

ChunChhau Liao
SCJP 1.4
SCWCD

[Tong Chen]

Congratulations to you!

[Chin Ho Tan]

Did you cache your records ? Or you just do "search" from the file directly ?

[Vlad Rabkin]

Hi Shan,
Waw: 100%. Congratulations!
Could please help me and answer 3 question:
Question 1
Could please describe you synchronization design (to guarantee data consistency):
1) Do you lock the record to read on the client also:
lock()-read()-lock() to read
lock()- read()-write()-unlock() to update
or
2) you don't lock() to read, but you synchronize all read/write methods in DBMain.
read() to read
lock()- read()-write()-unlock() to update?
Question 2
You said you use Data Model (represented by String[]).
Does it mean that you have a DataModel for each record?
How you class look like 1) or 2)

public DataModel{
 private String[] data;
 
 public String getField(int col){
   return data[col];
 }  
 public String getField(String col){
   ...
 } 
 public String getCount(){
   data.length;
 }
}
public DataModel{
 private String[] data;
 
 public String getName(){
   return data[1];
 } 
 public String getLocation(){
   return data[2];
 }
}

Could you describe more precisly what you meant?
Question 3
Did you do something do prevent client from been changed in case database structure changes (columns in database would be added, deleted, or replaced)? If so, what have done to prevent changes on clients if it occurs?
Many thanx,
Vlad
[ September 18, 2003: Message edited by: Vlad Rabkin ]
[ September 18, 2003: Message edited by: Vlad Rabkin ]