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.