What is the difference between a JavaBean and a POJO

Question

I m not sure about the difference  I m using Hibernate and  in some books  they use JavaBean and POJO as an interchangeable term  I want to know if there is a difference  not just in the Hibernate context  but as general concepts

User · Answer

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.

http://www.martinfowler.com/bliki/POJO.html

User · Answer

POJO   If the class can be executed with underlying JDK without any other external third party libraries support then its called POJO  JavaBean  If class only contains attributes with accessors setters and getters  those are called javabeans Java beans generally will not contain any bussiness logic rather those are used for holding some data in it   All Javabeans are POJOs but all POJO are not Javabeans

User · Answer

POJOS with certain conventions  getter setter public no-arg constructor  private variables  and are in action ex  being used for reading data by form  are JAVABEANS

User · Answer

In summary  similarities and differences are      java beans                           Pojo  -must extends serializable              -no need to extends or implement   or externalizable                       -must have public class                 - must have public class -must have private instance variables       -can have any access specifier variables  -must have public setter and getter method  - may or may not have setter or getter method  -must have no-arg constructor            - can have constructor with agruments    All JAVA Beans are POJO but not all POJOs are JAVA Beans

User · Answer

Java beans are special type of POJOs    Specialities listed below with reason

User · Answer

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

User · Answer

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

User · Answer

Pojo - Plain old java object  pojo class is an ordinary class without any specialties class totally loosely coupled from technology framework the class does not implements from technology framework and does not extends from technology framework api that class is called pojo class   pojo class can implements interfaces and extend classes but the super class or interface should not be an technology framework   Examples     1   class ABC  ----     ABC class not implementing or extending from technology framework that s why this is pojo class   2   class ABC extends HttpServlet  ---     ABC class extending from servlet technology api that s why this is not a pojo class   3   class ABC implements java rmi Remote  ----     ABC class implements from  rmi api that s why this is not a pojo class   4   class ABC implements java io Serializable  ---     this interface is part of java language not a part of technology framework so this is pojo class   5   class ABC extends Thread  --     here thread is also class of java language so this is also a pojo class   6   class ABC extends Test  --     if Test class extends or implements from technologies framework then ABC is also not a pojo class because it inherits the properties of Test class  if Test class is not a pojo class then ABC class also not a pojo class   7   now this point is an exceptional case   Entity class ABC  --      Entity is an annotation given by hibernate api or jpa api but still we can call this class as pojo class  class with annotations given from technology framework is called pojo class by this exceptional case

User · Answer

You ve seen the formal definitions above  for all they are worth   But don t get too hung up on definitions  Let s just look more at the sense of things here   JavaBeans are used in Enterprise Java applications  where users frequently access data and or application code remotely  i e  from a server  via web or private network  via a network  The data involved must therefore be streamed in serial format into or out of the users  computers - hence the need for Java EE objects to implement the interface Serializable  This much of a JavaBean s nature is no different to Java SE application objects whose data is read in from  or written out to  a file system  Using Java classes reliably over a network from a range of user machine OS combinations also demands the adoption of conventions for their handling  Hence the requirement for implementing these classes as public  with private attributes  a no-argument constructor and standardised getters and setters   Java EE applications will also use classes other than those that were implemented as JavaBeans  These could be used in processing input data or organizing output data but will not be used for objects transferred over a network  Hence the above considerations need not be applied to them bar that the be valid as Java objects  These latter classes are referred to as POJOs - Plain Old Java Objects   All in all  you could see Java Beans as just Java objects adapted for use over a network   There s an awful lot of hype - and no small amount of humbug - in the software world since 1995

[java] What is the difference between a JavaBean and a POJO?

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