POJO Classes

What are POJO Classes ?

• POJO stands for Plain Old Java Object.
• POJO is a simple Java class that doesn't adhere or follows to any specific conventions or interfaces.
• POJO class typically consists of :
  1. Private fields : Variables should be private to maintain encapsulation.
  2. Public getter and setter methods : To access and modify the private fields.
• For example :

  public class Student
  {
      private String name;
      private int rollno;
  
      // Constructor
      public Student(String name, int rollno)
      {
          this.name = name;
          this.rollno = rollno;
      }
  
      // Getter and setter methods
      public String getName()
      {
          return name;
      }
  
      public void setName(String name)
      {
          this.name = name;
      }
  
      public int getRollno()  
      {
          return rollno;
      }
  
      public void setRollno(int rollno)
      {
          this.rollno = rollno;  
  
      }
  }

  
  

Use of POJO Classes ?

• POJO classes are mainly used for data representation and data transfer.
• Below are some common uses of POJO classes :-
  1. Encapsulation : POJO classes encapsulate data in an object, making it easier to manage and access data using methods rather than exposing fields directly.
  2. Data Transfer : POJO classes are commonly used as Data Transfer Objects (DTOs), allowing the easy transfer of data between layers of an application (e.g., between a database and a frontend).
  3. Readability and Maintainability : POJO classes make the code cleaner and easier to maintain by clearly defining fields and providing accessor methods.
  4. Framework Compatibility : Most Java frameworks, such as Hibernate, Spring, and JPA, use POJO classes to map data from a database or an external source to an object.
  5. Testing : POJO classes can be used to create test data for unit and integration tests.

JavaBean Classes

What are JavaBean Classes ?

• A JavaBean is a specialized type of POJO that follows specific conventions :-
  1. Private Fields : Variables should be private to maintain encapsulation.
  2. Public Getter and Setter Methods : To access and modify the private fields.
  3. No-Argument Constructor : Enables instantiation of the JavaBean without setting any initial values.
  4. Serializable Interface : JavaBeans often implement Serializable for compatibility with certain frameworks.
• For example :

  public class Student implements Serializable
  {
      private String name;
      private int rollno;
  
      // No-argument constructor
      public Student() {}
  
      // Parameterized constructor (strictly not required but good practice)
      public Student(String name, int rollno)
      {
          this.name = name;
          this.rollno = rollno;
      }
  
      // Getter and setter methods
      public String getName()
      {
          return name;
      }
  
      public void setName(String name)
      {
          this.name = name;
      }
  
      public int getRollno()  
      {
          return rollno;
      }
  
      public void setRollno(int rollno)
      {
          this.rollno = rollno;  
  
      }
  }

  
  

Use of JavaBean Classes ?

• POJO classes are mainly used for data representation and data transfer.
• Below are some common uses of POJO classes :-
  1. Encapsulation : JavaBeans allow data encapsulation with strict conventions, providing standardized access and modification through getters and setters.
  2. Data Transfer : JavaBeans are frequently used as Data Transfer Objects (DTOs) for transferring data between application layers.
  3. Readability : JavaBeans are designed as reusable components in applications, promoting modularity and flexibility.
  4. Framework Compatibility : Frameworks like Spring and Hibernate rely on JavaBeans for object mapping, configuration, and data manipulation.
  5. Testing: JavaBean classes can be used to create test data for unit and integration tests.
  6. IDE Support and Interoperability : JavaBeans conventions allow easy integration with IDEs, simplifying tasks like visual component manipulation and automatic code generation.

Difference between POJO Classes & JavaBean Classes :-

Choosing between POJO and JavaBean :-

• POJO Classes : POJO Classes are used when we need a simple, plain Java object without any specific framework requirements.
• JavaBean Classes : JavaBean Classes are used when we need a more structured object that can be easily serialized, persisted and integrated with frameworks.