tailieunhanh - Chapter 16: Database Issues

Judge a man by his questions rather than his answers. –Voltaire A prudent question is one-half of wisdom. –Francis Bacon You’re on your own for the other half. –The Authors As with the previous chapter, this chapter asks—you got it—questions. Some will seem obvious, some won’t. But this is the area where your solution to the problem is going to have the greatest impact on your score. You’re going to be asked to build a database. | JAVA 2 SUN CERTIFIED PROGRAMMER DEVELOPER 16 Database Issues CERTIFICATION OBJECTIVE Understand Database Issues 2 Chapter 16 Database Issues CERTIFICATION OBJECTIVE Understand Database Issues Judge a man by his questions rather than his answers. Voltaire A prudent question is one-halfofwisdom. Francis Bacon You re on your own for the other half. The Authors As with the previous chapter this chapter asks you got it questions. Some will seem obvious some won t. But this is the area where your solution to the problem is going to have the greatest impact on your score. You re going to be asked to build a database. From scratch. And since there will be concurrent clients or at least the possibility of concurrent clients you ll have to be certain dead certain that you correctly manage record locking. How you implement your searching updating and locking mechanism is entirely up to you. Again there is definitely no One Right Answer for your solutions to these issues. But however you choose to do it be certain that the logic is sound. For example even if you never experience deadlock during testing if there s even the slightest possibility no matter how remote the chance that it could happen you could easily fail the exam even if nearly everything else in your application is perfect. The two biggest issues are locking and searching but locking is where the Big Money really is. We ll start with a brief overview of the key concepts followed by yet another inspiring list of thought-provoking questions. Building a Database If you remember from Chapter 11 you re the one who has to build the database the client s too cheap or neurotic to invest in a commercial database even a free one. So what is a database That depends on your assignment but for the purposes of the exam software-that-lets-you-access-a-set-of-records will do. You have some data in some file format somewhere with a known schema and your job is to write an Understand Database Issues 3 application that allows that