JavaBeans

JavaBeans are reusable software components for the Java platform. A JavaBean is a Java class that follows a set of conventions and design patterns that enable its properties to be accessed, inspected, and manipulated by development tools and frameworks. The core idea is to provide a simple, standardized way to encapsulate data with properties and behavior that can be manipulated visually in GUI builders and configured in IDEs.

Key conventions include a public no-argument constructor; private properties with public getter and setter methods following the naming pattern getProperty, setProperty (or isProperty for boolean fields); implements Serializable to support persistent storage or transmission; and well-formed encapsulation with predictable side effects. These conventions enable uniform access to a bean’s properties via reflection and introspection.

JavaBeans are commonly used as data carriers (plain old Java objects, or POJOs) with property descriptors that can be discovered at runtime through the Java Beans Introspector (java.beans.Introspector). Optional BeanInfo classes can provide explicit information about properties, methods, and events. JavaBeans can also fire property change events via PropertyChangeListener to support binding in UI frameworks.

In practice, JavaBeans underpin many GUI components and frameworks, especially in the Swing toolkit and various visual builders. They are not the same as Enterprise JavaBeans (EJB), which refers to a distinct server-side component model. While JavaBeans can be serialized, persistence and remote invocation are not inherent to the pattern and are typically addressed by other patterns or frameworks.