Hibernate id annotation

Hibernate id annotation

In this section, you will learn how to do mapping of id through annotation.

Since id / primary key is the most important field in the table, it uniquely identify a row in the table. You can also auto generate this using annotation @GeneratedValue. Given below a simple class file mapped to table Worker using annotation :

package worker;

import javax.persistence.*;

@Entity
@Table(name = "Worker")
public class Worker {
@Id
@GeneratedValue
@Column(name = "id")
private int id;

@Column(name = "first_name")
private String firstName;

@Column(name = "last_name")
private String lastName;

@Column(name = "salary")
private int salary;

public Worker() {
}

public Worker(String fname, String lname, int salary) {
this.firstName = fname;
this.lastName = lname;
this.salary = salary;
}

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}


public String getFirstName() {
return firstName;
}

public void setFirstName(String first_name) {
this.firstName = first_name;
}

public String getLastName() {
return lastName;
}

public void setLastName(String last_name) {
this.lastName = last_name;
}

public int getSalary() {
return salary;
}

public void setSalary(int salary) {
this.salary = salary;
}
}

Here, we are importing  javax.persistence to annotate the above class.  @Id annotation determines the primary key of entity.

The annotation @Id  can be applied to one of the following  field type :

• Java primitive type
  
  
• any primitive wrapper type
  
  
• String
  
  
• java.util.Date
  
  
• java.sql.Date
  
  
• java.math.BigDecimal
  
  
• java.math.BigInteger.