Java™ Application Development on Linux - Dator

14.10 Review32514.9.4 Straight JDBCOur application is quite simple. We’re going to directly integrate databaseaccess by simply calling the JDBC interface at startup and making use of thatconnection again and again for data changes.Our solution is more than sufficient for the standalone command-line andGUI versions of the application, but it will be left as an exercise for the readerto implement a better solution for the EJB implementation.What will be lacking? Well, the solution we will implement here will geta single database connection and use it throughout the life of the application.It will be assumed that a single thread is accessing the database. These are allbad assumptions for a multiuser and multithreaded environment such as anapplication server.14.9.4.1 Static Account MembersMost of the database code is in the Account class. It consists of a static method,getTopAccount(), which will establish a static connection to the database,create the Account table if need be, and load the top level account (defined asthe account record with a null parent) if present or create it if not present.The username is passed in as an argument. The username must exist inthe User table. If it does not, an exception is thrown.14.9.4.2 Joining the UserTwo static methods are added that take a JDBC Connection and a String asarguments. They are getUserIdByName() and getUserByName(). TheString is the username to look for. The first method returns the id columnfor that user. It returns zero (0) if the user doesn’t exist. The other returns aUser object, or null if the user doesn’t exist.14.10REVIEWWe briefly examined choices of Open Source SQL database servers. Wedescribed how to set up PostgreSQL.