Java™ Application Development on Linux - Dator

14.7 Beyond the Basics319files, and even when it is in files on the filesystem, you cannot, when you installa package like BudgetPro, simply put your database files in place, since thereare probably other applications that have their tables in those files, and replacingthem with yours would destroy that data.Often, the table creation statements and any initial table rows required areplaced in a SQL file and that file is run against the database. Meanwhile, all ofthe database code that performs application interactions is either in the applicationcode or in stored procedures called by the application code. But there isno fundamental reason to make this distinction. The application can see to itthat its database and tables are created.Of course, you can automate this setup with a shell script, but Java issupposed to be cross-platform. Of course, you can write a batch file for Windowsand a shell script for UNIX, but if you just put this setup into your Javacode, you don’t have to maintain and test separate installation procedures. Oneof the areas where Java applications tend to lag behind other applications is ininstallation and setup. You can obviate this somewhat by including databasesetup in your Java code, thus eliminating the need to write platform-specificscripts.Consider including your database and table creation statements directlyin your Java code, even if it is in a singleton setup class that only runs once.The basic tables should parallel the objects. So, for our classes, the SQLstatements to build the tables might look as shown in Example 14.1.For the moment, we are confining our table declarations to a form thatshould work with both Open Source databases.These are very basic definitions. We will be talking about issues like generatingunique IDs for records as we develop the code to back these. Differentdatabase products have different “best” solutions, which will make the supportfor multiple databases more problematic.14.7BEYOND THE BASICSWe are going to adopt a very simple strategy for database persistence. We aregoing to read in the data structures at startup and maintain them as changesare made during execution. That way, any abnormal termination will leave thedata in a recoverable state. The application will not require any “save”operation.