What is java pojo class, java bean, normal class?

Question

Possible Duplicate:
Difference between DTO, VO, POJO, JavaBeans?

Hi please don't say my question is duplicate :-) I saw all questions but didn't understand the exact difference.

Can someone explain what is POJO, Bean, Normal Class in easy language?

Solution 1

1. Normal Class: A Java class

2. Java Beans:

   • All properties private (use getters/setters)
   • A public no-argument constructor
   • Implements Serializable.

3. Pojo: Plain Old Java Object is a Java object not bound by any restriction other than those forced by the Java Language Specification. I.e., a POJO should not have to

   • Extend prespecified classes
   • Implement prespecified interface
   • Contain prespecified annotations

Solution 2

POJO stands for Plain Old Java Object, and would be used to describe the same things as a "Normal Class" whereas a JavaBean follows a set of rules. Most commonly Beans use getters and setters to protect their member variables, which are typically set to private and have a no-argument public constructor. Wikipedia has a pretty good rundown of JavaBeans: http://en.wikipedia.org/wiki/JavaBeans

POJO is usually used to describe a class that doesn't need to be a subclass of anything, or implement specific interfaces, or follow a specific pattern.

Solution 3

POJO = Plain Old Java Object. It has properties, getters and setters for respective properties. It may also override Object.toString() and Object.equals().

Java Beans : See Wiki link.

Normal Class : Any java Class.

Comments

[simap]

also, JavaBeans should implement the Serializable interface.

[Siva]

I heard except no-argument constructor both pojo and bean are same right ?

[Siva]

java bean, implement Serializable means every time we must implement Serializable manually ?

[Siva]

A public no-argument constructor: I think every class has its own no-argument constructor if am correct, why you specified only for bean only ? sorry if am wrong am fresher.

[pathe.kiran]

if you did not specify any constructor for a class then only java will create no-argument constructor implicitly.

[firstpostcommenter]

So all normal Java classes are POJOs?

[THIS USER NEEDS HELP]

@firstpostcommenter It might be useful to get a description of what POJO is from the person who coined the term. ("encoding business logic into regular java objects rather than using Entity Beans"). In other words, POJO was a name to given to describe "plain old java objects" in order to contrast Java beans. POJOs are domain/business objects specific, so not necessarily all Java classes are POJOs

[shikher.mishra]

the only difference between a POJO and Beans is that Beans should implement Serializable interface?

[Asif Mushtaq]

I didn't during creating a bean in spring.