Java Cookbook

Chapter 20. Database Access

Introduction

Java can be used to access many kinds of databases. A database can be something as simple as a text file or a fast key/value pairing on disk (DBM format), as sophisticated as a relational database management system (DBMS), or as exotic as an object database.

Regardless of how your data is actually stored, in a reasonable application you’ll want to write a class called an accessor to mediate between the database and the rest of the application. For example, if you are using JDBC, the answers to your query will come back packaged in an object called a ResultSet, but it would not make sense to structure the rest of your application around the ResultSet because it’s JDBC-specific. In a Personal Information Manager application, for example, the primary classes might be Person, Address, and Meeting. You would probably write a PersonAccessor class to request the names and addresses from the database (probably using JDBC), and generate Person and Address objects from them. The DataAccessor objects would also take updates from the main program and store them into the database.^[46]

Java DataBase Connectivity (JDBC) consists of classes in package java.sql and some JDBC Level 2 extensions in package javax.sql. (SQL is the Standard Query Language, used by relational database software to provide a standard command language for creating, modifying, updating, and querying relational databases.)

Why was JDBC invented? Java is highly portable, but many databases ...