What is the difference between a JavaBean and a POJO?
A JavaBean follows certain conventions. Getter/setter naming, having a public default constructor, being serialisable etc. See JavaBeans Conventions for more details.
A POJO (plain-old-Java-object) isn't rigorously defined. It's a Java object that doesn't have a requirement to implement a particular interface or derive from a particular base class, or make use of particular annotations in order to be compatible with a given framework, and can be any arbitrary (often relatively simple) Java object.
All JavaBeans are POJOs but not all POJOs are JavaBeans.
A JavaBean is a Java object that satisfies certain programming conventions:
- the JavaBean class must implement either Serializable or Externalizable;
- the JavaBean class must have a public no-arg constructor;
- all JavaBean properties must have public setter and getter methods (as appropriate);
- all JavaBean instance variables should be private.
According to Martin Fowler a POJO is an object which encapsulates Business Logic while a Bean (except for the definition already stated in other answers) is little more than a container for holding data and the operations available on the object merely set and get data.
The term was coined while Rebecca Parsons, Josh MacKenzie and I were preparing for a talk at a conference in September 2000. In the talk we were pointing out the many benefits of encoding business logic into regular java objects rather than using Entity Beans. We wondered why people were so against using regular objects in their systems and concluded that it was because simple objects lacked a fancy name. So we gave them one, and it's caught on very nicely.