JPA Creating an Entity

A Java class can be easily transformed into an entity. For transformation the basic requirements are: -

No-argument Constructor
Annotation

Here, we will learn how to transform a regular Java class into an entity class with the help of an example: -

Simple Student class

public class Student {
	
	private int id;
	private String name;
	private long fees;
	public Student() {}
	public Student(int id) 
	  {
		this.id = id;
		 }
	public int getId() 
	 {
		return id;
		 }
	public void setId(int id)  
	 {
		this.id = id;
		 }
	public String getName()
	 {
		return name; 
		 }
	public void setName(String name) 
	 {
		this.name = name;
		 }
	public long getFees()
	 {
		return fees;
		 }
	public void setFees (long fees)
	 {
		this.fees = fees;
	 } 
}

Above class is a regular java class having three attributes id, name and fees. To transform this class into an entity add @Entity and @Id annotation in it.

@Entity - This is a marker annotation which indicates that this class is an entity. This annotation must be placed on the class name.
@Id - This annotation is placed on a specific field that holds the persistent identifying properties. This field is treated as a primary key in database.

Simple Entity Class

import javax.persistence.*;
@Entity
public class Student {
	@Id
	private int id;
	private String name;
	private long fees;
	public Student() {}
	public Student(int id) 
	 {
		this.id = id;
		 }
	public int getId() 
	 {
		return id;
		 }
	public void setId(int id) 
	 {
		this.id = id;
		 }
	public String getName()
	 {
		return name; 
		 }
	public void setName(String name) 
	 {
		this.name = name;
		 }
	public long getFees()
	 {
		return fees;
		 }
	public void setFees (long fees)
	 {
		this.fees = fees;
	 } 
}

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