Java Cryptography

The Provider Architecture

At the root of the JCA is the idea of security providers. A provider supplies algorithms for the cryptographic concept classes. In practice, a provider is a collection of algorithm classes headed up by a java.security.Provider object. This is confusing terminology; provider (small p) refers to the concept, while Provider refers to a specific class.

What Are Factory Methods?

You’ll recall that classes can define both class methods and instance methods. The class methods are usually called static methods and are defined using the static keyword. The instance methods are just called methods. Static methods don’t need an instance to run. main(), for example, is a famous static method. Regular instance methods are always run on a particular instance of a class and typically manipulate its data or call other instance methods.

A factory method, then, is a special kind of static method that returns an instance of a class. In JDK 1.0.2, factory methods were used indirectly in the Socket class (see setSocketImplFactory()). In JDK 1.1 and later, factory methods are much more prevalent. They are sprinkled throughout the java.text package as well as the java.security package. By convention, factory methods are named getInstance().

A factory method is an example of a design pattern, a pattern of programming that turns up again and again in object-oriented programming. For a thorough and interesting treatment of design patterns, take a look at Design Patterns: Elements of ...