POJO Class in Java

POJO in Java refers to a Plain Old Java Object. It is a typical item that is not restricted by any specific limitations. A distinct classpath is not required for the POJO file. It enhances the readability and reusability of a Java program.

Due to their ease of maintenance, POJOs are now widely recognized. They are easy to read and write. A POJO class does not have a naming convention for its properties and methods. It can be utilized by any Java application and is independent of any Java Framework.

A POJO Class in Java typically contains variables, along with corresponding Getters and Setters.

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What is a POJO Class?

A Plain Old Java Object or POJO represents basic Java classes that lack both extended and implemented features in specific Java constructs and serve to organize data for clear reuse. POJOs are not tied to any particular framework, which makes them flexible and simple to use. They are mainly utilized for data encapsulation and representing objects in an object-oriented style.

Essential Features of a POJO Class:

• No Inheritance: A POJO class does not derive from or implement any specific classes or interfaces tied to a framework (for example, Serializable, Cloneable, or any framework-specific interfaces such as JpaRepository).
• Private Attributes: POJO classes typically have private instance variables (attributes) to hold the object's state or data. This aligns with the encapsulation principle found in object-oriented programming.
• Public Getters and Setters: POJOs offer public methods (getters and setters) for accessing and altering the private attributes. This provides regulated access to the object's internal state.
• Default Constructor: A POJO typically contains a no-argument (default) constructor, but it may also feature parameterized constructors for ease of use.
• Override Methods (Optional): POJOs may optionally override methods such as toString(), equals(), and hashCode() to deliver meaningful string representations and comparison functionality for the object.
• Lightweight: POJOs lack intricate logic or framework dependencies, which makes them simple to comprehend, maintain, and utilize across different sections of a program.

Difference Between POJO and JavaBeans

Also Read: Annotations in Java: Types, Uses and Examples

Creating a Simple POJO Class

Creating a basic POJO (Plain Old Java Object) class within a Java framework requires basic knowledge of programming. A POJO demonstrates the following characteristics in general:

• Private attributes used to denote information.
• The class implements a constructor to initialize its fields.
• Use Getter and Setter methods to read and write to the fields.
• Optional methods for object representation as strings and object comparison can be added through the implementation of toString(), equals(), and hashCode().

Let’s develop a Car POJO as a sample.

A Step-by-Step Illustration of a Basic POJO Class in Java

• Define the class with public accessibility.
• Establish private attributes to hold the object's information.
• Create a constructor to set up the attributes.
• Create getters and setters to access and change fields.
• (Optionally) Add toString(), equals(), and hashCode() methods.

Example Code: Car POJO

public class Car {
   // Step 1: Declare private fields
   private String model;
   private int year;
   // Step 2: Create a constructor to initialize the fields
   public Car(String model, int year) {
       this.model = model;
       this.year = year;
   }
   // Step 3: Getter for model
   public String getModel() {
       return model;
   }
   // Step 4: Setter for model
   public void setModel(String model) {
       this.model = model;
   }
   // Step 3: Getter for year
   public int getYear() {
       return year;
   }
   // Step 4: Setter for year
   public void setYear(int year) {
       this.year = year;
   }
   // Optional: Step 5 - toString() method for easy object representation
   @Override
   public String toString() {
       return "Car{model='" + model + "', year=" + year + "}";
   }
   // Optional: Step 6 - equals() method to compare objects
   @Override
   public boolean equals(Object obj) {
       if (this == obj) return true;
       if (obj == null || getClass() != obj.getClass()) return false;
       Car car = (Car) obj;
       return year == car.year && model.equals(car.model);
   }
   // Optional: Step 6 - hashCode() method to generate unique hash for the object
   @Override
   public int hashCode() {
       return 31 * model.hashCode() + year;
   }
}

Explanation of Each Part:

• Private Fields:

The code defines two variables using the private access modifier: String model and int year, which store car information. The fields maintain private access since encapsulation principles require them to remain inaccessible to external code.

• Constructor:

The constructor public Car(String model, int year) accepts input parameters to set the fields whenever the program instantiates a Car object.

• Setter and Getter Methods:

Through getYear() and getModel(), the program enables other sections to access model and year values.

Other code sections can modify the values of model and year through the setModel() and setYear() methods.

• toString():

API method toString() generates an object string that helps developers perform debugging while maintaining records of object states.

• equals() and hashCode():

When executing the equals() method, it checks whether two Car objects have matching model types and years.

hashCode() produces a hash code for the object, which is beneficial for saving objects in collections such as HashMap or HashSet.

Example Usage of the POJO Class:

public class Main {
   public static void main(String[] args) {
       // Create a new Car object using the constructor
       Car myCar = new Car("Toyota Camry", 2020);
       // Print out the car object using the toString() method
       System.out.println(myCar);  // Output: Car{model='Toyota Camry', year=2020}
       // Access car properties using getters
       System.out.println("Model: " + myCar.getModel());  // Output: Model: Toyota Camry
       System.out.println("Year: " + myCar.getYear());    // Output: Year: 2020
       // Modify car properties using setters
       myCar.setModel("Honda Accord");
       myCar.setYear(2022);
       // Print out the updated car object
       System.out.println(myCar);  // Output: Car{model='Honda Accord', year=2022}
   }
}

Output:

Car{model='Toyota Camry', year=2020}
Model: Toyota Camry
Year: 2020
Car{model='Honda Accord', year=2022}

Understanding POJO Structure

Grasping the layout of a POJO (Plain Old Java Object) is crucial for creating straightforward and efficient Java classes that symbolize real-world objects or data without needing intricate dependencies or frameworks.

Here is an overview of the POJO structure and its essential elements:

• Class Declaration

A POJO class is a standard Java class that has a clear structure and is independent of any particular framework or library.

POJOs exist without any restriction on inheritance from or implementation of particular interfaces or classes. They are self-sufficient and nimble.

• Private Fields

A standard POJO comprises private fields as its instance variables for representing its data state. The fields remain hidden from external access because they are encapsulated with the goal of maintaining authorization control.

By using private fields, developers achieve protected object states because they apply encapsulation from Object-Oriented Programming (OOP).

• Public Getters & Setters

The class's private attributes need Getter and Setter functions to provide read-write capabilities.

The getter operation reveals the field value, but the setter function makes field value modifications.

Data encapsulation through private variables becomes possible by using getter and setter methods for regulated access control.

• toString()

Another essential functionality of the class uses a toString() redefinition to produce string outputs that help with troubleshooting and logging activities.

The usage of toString() is not essential when working with POJOs, yet implementation is recommended.

• equals() & hashCode()

POJOs override the equals() and hashCode() methods when they need to support object comparison operations and ensure correct mapping internals in HashMap and HashSet structure management.

The methods must be implemented in POJOs whenever collection storage operations do not require them.

Why Use POJO Classes?

The principal benefits of using POJO classes in Java applications consist of:

• Clarity and Comprehensibility:

The simplicity of generating and understanding, and using POJOs promotes clean coding practices.

• Reusability:

A POJO class becomes reusable as it is stable enough to function in multiple project sections and application parts.

• Adaptability:

Because POJOs have no framework restriction,s they offer more extensive integration capabilities and higher flexibility.

• Verifiability:

Testing becomes simpler with POJOs because the dependencies tend to remain straightforward.

• Encapsulation:

Programmers must call methods on POJO classes rather than directly accessing variables because this practice helps defend against security risks.

• Verification:

The verification process becomes possible when POJO classes use setter methods to validate value accuracy.

• Debugging:

Programmers can locate and debug their code during value retrieval and modifications through the use of breakpoints in getter and setter methods in POJO classes.

• Interoperability:

POJOs enable cooperation with all forms of Java-based technologies, including servlets, JSP, and EJB.

• Information Transfer:

The majority of development frameworks utilize POJOs as data transfer objects (DTOs) together with entity classes or model classes across different applications.

• Serialization/Deserialization:

The Java objects created from complicated data structures such as JSON and XML can be translated back and forth through the use of POJOs.

POJO vs JavaBeans vs DTO

When working with Java, it's essential to understand the differences between POJOs, JavaBeans, and DTOs. Each serves a unique purpose in object-oriented design, with distinct characteristics that impact their use in applications. The following table compares these three key concepts to help clarify their roles and applications in Java development

Also Read: What is Composition in Java With Examples

POJO with Constructors

A POJO (Plain Old Java Object) with constructors refers to a Java class that includes one or more constructors to initialize its objects. Constructors in a POJO class serve to offer various methods for creating the object, and they can either be default constructors (without arguments) or parameterized constructors (with arguments).

This is how to create a POJO class with constructors in Java:

Example of a POJO featuring Constructors

Suppose we aim to develop a Car POJO that has two attributes: model (String) and year (int). We will add a no-argument constructor along with a parameterized constructor.

Example Code:

public class Car {
    private String model;
    private int year;
    // No-argument constructor (default constructor)
    public Car() {
        // You can initialize the fields with default values if needed
        this.model = "Unknown";
        this.year = 0;  // Default year, can be updated later
    }
    // Parameterized constructor to initialize the object with specific values
    public Car(String model, int year) {
        this.model = model;
        this.year = year;
    }
    // Getter for model
    public String getModel() {
        return model;
    }
    // Setter for model
    public void setModel(String model) {
        this.model = model;
    }
    // Getter for year
    public int getYear() {
        return year;
    }
    // Setter for year
    public void setYear(int year) {
        this.year = year;
    }
    // Override toString() to provide a string representation of the object
    @Override
    public String toString() {
        return "Car{model='" + model + "', year=" + year + "}";
    }
}

Explanation

• Constructor without parameters:

The no-argument constructor is offered to facilitate the creation of default objects. It sets the fields to default values, which can later be modified via setters or directly through methods in different sections of the application.

• Constructor with Parameters:

The parameterized constructor enables you to define particular values while instantiating a Car object. It sets the fields using the values provided to the constructor.

• Getters & Setters

The getters and setters are available to access and change the private fields. This adheres to the concept of encapsulation in Java.

• toString():

The toString() method is redefined to produce a string representation of the object that is easily understandable to humans. This is beneficial for debugging and logging activities.

The no-argument constructor is frequently utilized when dealing with frameworks such as Hibernate, JPA, or Spring, as these frameworks rely on reflection to create POJOs. Parameterized constructors are useful when you want to guarantee that an object is initialized with specific values right after it is created, minimizing the necessity for later setter invocations.

Best Practices for POJO Classes

Several recommended approaches exist for developing and working with POJO classes.

Encapsulation: Utilize Private Attributes with Public Setters/Getters

Your application should have getter and setter methods which regulate access to private members. Your POJO's interface stays unchanged since this method enables you to add validation or extra logic at any time.

Application of Constructors

Ensure the POJO functions with frameworks that need default object instantiation through the implementation of a no-argument constructor.

The class needs a constructor that takes parameters to enhance the process of object instantiation.

• Rewrite equals() and hashCode()

It is essential to create both an equals() method and a hashCode() method at the same time. The objects which equal() are determined to be equivalent need to produce identical hash code values.

Modify toString() for Clear Output

POJOs should contain an override of the toString() method, which produces an easily decipherable string view of the object data.

Select immutable POJOs as the primary choice for applicability

You should make all POJOs immutable when possible through several measures including making fields final and eliminating setter methods before the constructor finishes the object setup.

• Setting fields as final.
• Omitting setter methods.
• Executing the constructor with the completion of object setup.

Refrain from Including Business Logic in POJOs

Every business validation and execution logic must stay inside dedicated service classes. POJOs should keep information only while they can present methods that carry out basic field computations.

Utilize Serializable When Required

Make POJOs Serializable only when necessary. Serialization may introduce additional overhead, and not every POJO requires serialization.

Real-World Applications of POJO Classes

Here are several practical scenarios where POJO classes are commonly utilized:

Representación de Entidades en Base de Datos (ORM con Hibernate o JPA)

In applications that utilize Object-Relational Mapping (ORM) frameworks such as Hibernate or JPA (Java Persistence API), POJOs serve to depict database entities. Database tables have corresponding entities written as POJOs.

Application: For handling permanent data in business applications, such as online shopping sites, customer relationship management systems, or financial applications.

1. Data Transfer Objects (DTO) within Distributed Systems

The majority of times POJOs function as Data Transfer Objects (DTOs) to transfer data throughout different application sections and server-client distributed setups.

Application: In RESTful web services, microservices, and client-server applications.

2. Configuration Information in Java-oriented Frameworks (Spring)

In frameworks such as Spring, POJOs serve to depict configuration information. These POJOs are frequently associated with configuration properties or beans.

Application: In Spring Boot applications, @ConfigurationProperties is frequently utilized to map configuration values to POJOs.

3. Session Handling in Web Applications

POJOs are frequently utilized to depict session information in web applications. They retain short-term data regarding the user's session while they engage with a web application.

Application: For e-commerce, booking platforms, and monitoring user activity.

Also Read: What is MVC Architecture in Java? A Complete Guide to Components and Applications in 2025

Common Interview Questions on POJO

Q: Is it possible for a POJO class to implement interfaces?

A: Yes, a POJO class may implement interfaces, although it isn't required. In reality, POJOs are typically simple objects that do not rely on any frameworks or particular interfaces. Nonetheless, if necessary, a POJO can implement any interface (such as Serializable or user-defined interfaces) to satisfy particular needs.

Q: What does the hashCode() method do in a POJO?

A: The hashCode() method in a POJO produces a hash code value that aids in determining object equality, particularly when objects are kept in hash-based collections such as HashSet, HashMap, and Hashtable. The hashCode() function must align with the equals() function, indicating that if two objects are equal (as defined by equals()), they should have identical hash codes.

Q: Is it possible for POJOs to contain business logic?

A: Indeed, POJOs may contain business logic. Although POJOs are mainly utilized for storing data, it is fairly common to incorporate some simple logic within a POJO (for instance, methods to compute values, check data validity, etc.). Nonetheless, it is generally advisable to separate business logic from POJOs and implement it in service classes to uphold the separation of concerns.

Q: What does Serializable mean in a POJO?

A: The Serializable interface enables a POJO to be transformed into a byte stream, which can be stored in a file or transmitted across a network. This is crucial when you need to maintain the status of an object or move it between various components of a distributed system. Using Serializable allows the object to be serialized and deserialized when required.

Q: What function do getters and setters serve in POJOs?

A: Getters and setters are functions in a POJO that allow access to the class's private attributes. The getter method is employed to obtain the value of a private attribute, while the setter method serves to change the value of a private attribute. These techniques facilitate encapsulation, a key principle in object-oriented programming.

Practice Exercise Suggestion

Exercise 1: Create a POJO Class for a Car Entity

This is a simple POJO class for a Car entity written in Java. This class may symbolize a vehicle in a database application, featuring attributes such as id, make, model, year, and price. It features fundamental JPA annotations to associate it with a database table if utilized in a Spring Boot or Java Persistence API (JPA) application.

Example Code:

import javax.persistence.*;
@Entity
@Table(name = "cars")  // Optional: specify the table name in the database
public class Car {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)  // Auto-generates the ID value
    private Long id;
    @Column(name = "make", nullable = false)  // The car's manufacturer
    private String make;
    @Column(name = "model", nullable = false)  // The car's model
    private String model;
    @Column(name = "year")  // The year of manufacture
    private int year;
    @Column(name = "price")  // The price of the car
    private double price;
    // Constructors
    public Car() { }  // Default constructor
    public Car(String make, String model, int year, double price) {
        this.make = make;
        this.model = model;
        this.year = year;
        this.price = price;
    }
    // Getters and Setters
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getMake() {
        return make;
    }
    public void setMake(String make) {
        this.make = make;
    }
    public String getModel() {
        return model;
    }
    public void setModel(String model) {
        this.model = model;
    }
    public int getYear() {
        return year;
    }
    public void setYear(int year) {
        this.year = year;
    }
    public double getPrice() {
        return price;
    }
    public void setPrice(double price) {
        this.price = price;
    }
    // Optional: Override toString, equals, and hashCode methods for better object representation
    @Override
    public String toString() {
        return "Car{id=" + id + ", make='" + make + "', model='" + model + "', year=" + year + ", price=" + price + '}';
    }
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Car car = (Car) o;
        return year == car.year && Double.compare(car.price, price) == 0 && make.equals(car.make) && model.equals(car.model);
    }
    @Override
    public int hashCode() {
        return Objects.hash(make, model, year, price);
    }
}

Explanation:

• Annotations:

To mark the class as an entity for JPA this annotation must be applied. It demonstrates the database table relation.

@Table(name = "cars"): Defines the name of the table in the database. RDBMS entities typically draw their name from the class definition (car) yet you maintain the freedom to alter this variable when needed.

@Id: Designates the id field as the main key.

@GeneratedValue: It provides instructions about how primary keys are automatically generated through the auto-increment feature managed by the database.

@Column: The @Column annotation maps database fields with table columns. The system attribute nullable = false creates mandatory non-empty values.

Characteristics (Fields):

• id: The distinct identifier for every Car entry.
• manufacturer: The producer of the vehicle (e.g., Toyota, Ford).
• make: The make of the car (e.g., Toyota, Ford).

The production year serves as the field attribute in the database.

Database costs include the price of the vehicle.

Constructors:

The application includes a no-argument constructor because JPA requires a default constructor.

The constructor includes input parameters through which users can initialize the fields.

Access to attributes happens through Getters, together with Setters, which operate as special functions. Every JPA implementation, including Spring framework, makes use of getter functions to fetch and setter functions to set field values.

Alternative Approaches:

The method toString() returns an object in a readable string format used for debugging needs.

The customer compares and generates hash codes in objects through equals() and hashCode(). When managing collections and regarding equality comparisons of Car objects, the equals() and hashCode() functions prove beneficial.

Code:

public class Main {
    public static void main(String[] args) {
        Car car = new Car("Toyota", "Corolla", 2022, 25000.0);
        System.out.println(car);
    }
}

Output:

Car{id=null, make='Toyota', model='Corolla', year=2022, price=25000.0}

Exercise 2: Implement a POJO with Parameterized Constructors -H3

Here’s an illustration of a POJO class in Java featuring a parameterized constructor, basic attributes, as well as getters, setters, and various standard methods. The class will embody a Person entity, but you can modify it for any other field you are engaged in.

Example Code:

public class Person {
    // Fields (Attributes)
    private String name;
    private int age;
    private String address;
    
    // Parameterized constructor to initialize fields
    public Person(String name, int age, String address) {
        this.name = name;
        this.age = age;
        this.address = address;
    }
    // Getter for name
    public String getName() {
        return name;
    }
    // Setter for name
    public void setName(String name) {
        this.name = name;
    }
    // Getter for age
    public int getAge() {
        return age;
    }
    // Setter for age
    public void setAge(int age) {
        this.age = age;
    }
    // Getter for address
    public String getAddress() {
        return address;
    }
    // Setter for address
    public void setAddress(String address) {
        this.address = address;
    }
    // Override toString() for a better string representation of the object
    @Override
    public String toString() {
        return "Person{name='" + name + "', age=" + age + ", address='" + address + "'}";
    }
    // Optionally override equals() and hashCode() if needed
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Person person = (Person) o;
        return age == person.age && name.equals(person.name) && address.equals(person.address);
    }
    @Override
    public int hashCode() {
        return Objects.hash(name, age, address);
    }
}

Explanation

• Characteristics (Domains):

name: Records the individual's name.

age: Keeps track of the individual's age.

location: Keeps the individual's location.

• Parameterized Constructor:

The constructor enables you to set all the fields while instantiating the Person class.

Getter and setter functions are available for every field, enabling access and alteration of the fields once the object has been instantiated.

• toString() Function:

The toString() method is redefined to provide a more user-friendly string depiction of the object. This is useful for troubleshooting or recording.

• equals() and hashCode() Functions:

These methods are modified to enable the comparison of Person objects according to their field values (name, age, and address).

equals() verifies whether two Person objects are identical by comparing their attributes.

hashCode() guarantees consistency for objects kept in hash-based collections (such as HashSet or HashMap).

Output:

Person{name='Alice', age=25, address='456 Park Ave'}
false
26

Exercise 3: Add toString(), equals(), and hashCode() Methods to an Existing POJO

Here is an illustration of how to incorporate the toString(), equals(), and hashCode() methods into an existing POJO class in Java.

Example Code:

import java.util.Objects;
public class Book {
    // Fields (Attributes)
    private String title;
    private String author;
    private String isbn;
    private double price;
    // Parameterized constructor
    public Book(String title, String author, String isbn, double price) {
        this.title = title;
        this.author = author;
        this.isbn = isbn;
        this.price = price;
    }
    // Getters and Setters
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public String getAuthor() {
        return author;
    }
    public void setAuthor(String author) {
        this.author = author;
    }
    public String getIsbn() {
        return isbn;
    }
    public void setIsbn(String isbn) {
        this.isbn = isbn;
    }
    public double getPrice() {
        return price;
    }
    public void setPrice(double price) {
        this.price = price;
    }
    // Override toString() method for better string representation
    @Override
    public String toString() {
        return "Book{" +
                "title='" + title + '\'' +
                ", author='" + author + '\'' +
                ", isbn='" + isbn + '\'' +
                ", price=" + price +
                '}';
    }
    // Override equals() method to compare Book objects
    @Override
    public boolean equals(Object o) {
        if (this == o) return true; // If both are the same object
        if (o == null || getClass() != o.getClass()) return false; // Null check and type check
        Book book = (Book) o; // Cast the object to Book type
        return Double.compare(book.price, price) == 0 && // Compare price (handling precision)
               Objects.equals(title, book.title) && // Compare title
               Objects.equals(author, book.author) && // Compare author
               Objects.equals(isbn, book.isbn); // Compare ISBN
    }
    // Override hashCode() method for consistent hashing based on fields
    @Override
    public int hashCode() {
        return Objects.hash(title, author, isbn, price); // Generate a hash code based on attributes
    }
}

Explanation:

• toString() Function:

This technique offers a string depiction of the Book object, which aids in logging or troubleshooting. It yields a string that presents the values of every field in an easy-to-read format.

Book{title='The Great Gatsby', author='F. Scott Fitzgerald', isbn='9780743273565', price=10.99}

• equals() Function:

This approach verifies the equality of two Book objects by assessing their attributes (title, author, isbn, and price).

The Double.compare() method is utilized to securely compare the price field as it is a floating-point number (it addresses precision concerns).

Objects.equals() is utilized to compare the string attributes (title, author, isbn) to prevent NullPointerException.

• hashCode() Function:

This technique produces a hash code for the Book instance derived from its attributes. The Objects.hash() function serves to create a hash code derived from several fields. It guarantees alignment between equals() and hashCode().

Code:

public class Main {
    public static void main(String[] args) {
        Book book1 = new Book("Java Basics", "John Doe", "1234567890", 39.99);
        Book book2 = new Book("Java Basics", "John Doe", "1234567890", 39.99);
        System.out.println(book1); // Prints book details
        System.out.println("Are both books equal? " + book1.equals(book2)); // Checks equality
    }
}

Output:

Book{title='Java Basics', author='John Doe', isbn='1234567890', price=39.99}
Are both books equal? true

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Student enrollment delivers both basic and advanced topics related to Java and object-oriented principles, and also introduces students to POJOs and inheritance alongside encapsulation and additional topics.

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• UpGrad programs provide thorough lessons on Java database integration which teach students to handle POJOs and JPA for creating applications that access databases effectively.
• Phased Industrial Education Includes Training Under Veteran Teachers While Gaining Familiarity with Regular Business Tools and Standards.
• After course completion, you will receive a certification as proof of your skills, which builds your career potential.

Relevant courses for you to explore:

• Core Java Basics
• JavaScript Basics from Scratch
• Data Structures & Algorithms
• AI-Powered Full Stack Development Course by IIITB

Starting your Java development training at upGrad will provide you with essential practical skills and introductory lessons about POJOs and additional subjects. Why delay? Visit an upGrad center and begin your educational adventure now!

Similar Reads:

• Java Tutorial: Learn Java Programming From Scratch For Beginners
• Java Hello World Program
• Java Classes and Objects
• Java OOPs Concepts
• Packages in Java

FAQs

What is a POJO class in Java?

In Java, a POJO, or Plain Old Java Object, is a simple, standard Java class that isn't tied to any specific framework or convention, making it reusable and easy to understand.

Why is POJO used in Java?

POJOs are used for increasing the readability and reusability of a program. POJOs have gained the most acceptance because they are easy to write and understand. POJO has no particular naming convention for properties and methods, or any other special restrictions.

What are the main characteristics of a POJO?

A POJO (Plain Old Java Object) is a simple Java class, not tied to any specific framework, and characterized by simplicity, reusability, and ease of understanding, focusing on data representation rather than framework-specific logic.

Is a POJO always serializable?

All JavaBeans are POJOs but not all POJOs are JavaBeans. Serializable, i.e. they should implement the Serializable interface. Still, some POJOs that don't implement a Serializable interface are called POJOs because Serializable is a marker interface and therefore not of many burdens.

Are getters and setters mandatory in a POJO?

No, getters and setters are not mandatory in a Plain Old Java Object (POJO). A POJO is a simple Java object that doesn't extend or implement any specialized classes or interfaces, and it typically represents a data structure. While it's common practice to use getters and setters to access the fields of a POJO (especially when encapsulation is required), they are not a strict requirement.

How do POJO classes work with Hibernate?

In Hibernate, POJO (Plain Old Java Object) classes represent database entities, and Hibernate uses these classes to map database tables to Java objects, allowing for object-relational mapping (ORM). You can think of POJOs as the building blocks for your data model, and Hibernate handles the persistence and retrieval of these objects to and from the database.

How is POJO used in Spring Boot?

In Spring Boot, POJOs (Plain Old Java Objects) are commonly used to represent data models, request/response bodies, and configuration properties. Spring Boot leverages POJOs for various purposes, primarily for creating Java objects that are easy to manage and work with within the Spring context.

How do you convert a POJO to JSON?

To convert a Java POJO to JSON using Jackson, you can follow these steps:

Add the Jackson library to your project dependencies.

Create an instance of the ObjectMapper class from Jackson.

Use the writeValueAsString() method of the ObjectMapper instance to serialize the Java object to JSON format.

How do you implement a POJO in a database application?

Create a POJO class object.

Set the values using the values from the database table.

Get the values using the get() method.

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