JavaBeans

JavaBeans (thereafter referred to as beans) are reusable software components that are written in the Java programming language and can be manipulated by using beans-aware builder tools. Because the beans are reusable, you can use them to construct more complex components, build new applications, or add functionality to existing applications. You can interact with beans visually, by using a builder, or manually, by calling the beans methods from a program.

Beans define a design-time interface that allows application builder tools to query components to determine the kinds of properties these components define and the kinds of events they generate (or to which they respond). You do not need to use special introspection and construction tools when working with beans. The pattern signatures are defined and can be easily recognized and understood by visual inspection.

Beans have the following characteristics:
Introspection
Introspection is the process by which a builder tool determines and analyzes how a bean works at design and run time. Because the beans are coded with predefined patterns for their method signatures and class definitions, tools that recognize these patterns can "look inside" a bean to determine its properties and behavior. Each bean has a related bean information class, which provides property, method, and event information about the bean itself. Each bean information class implements a BeanInfo interface, which explicitly lists the bean features that are exposed to application builder tools.
Properties
Properties control the appearance and behavior of a bean. Builder tools perform introspection on a bean to discover its properties and to expose those properties for manipulation, which allows you to change the property of a bean at design time.
Customization
The exposed properties of a bean can be customized at design time. Customization allows you to alter the appearance and behavior of a bean. Beans support customization by using property editors or by using special, sophisticated bean customizers.
Events
Beans use the Java event model to communicate with other beans. Beans can fire events. When a bean fires an event it is considered a source bean. A bean can also receive an event, in which case it is considered a listener bean. A listener bean registers its interest in the event with the source bean. Builder tools use introspection to determine those events that a bean sends and those events that it receives.
Persistence
Beans use Java object serialization, by implementing the java.io.Serializable interface, to save and restore states that might have changed as a result of customization. For example, when an application customizes a bean in an application builder, the state is saved so that any changed properties can be restored at a later time.
Methods
All bean methods are identical to methods of other Java classes. Bean methods can be called by other beans or through scripting languages.