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

 

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