JPA Creating an Entity

by Online Tutorials Library July 14, 2022

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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