Why fields marked as final or static not saved in database

Question

I have marked a field as static in a bean class and it is not saved in database. can someone explain it why the static fields are not persisted.

import java.util.Date;

import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Lob;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@Entity
@Table(name="USER_DETAILS")
public class UserDetails {

    @Id
    @Column(name="USER_ID")
    private int userId;

    private static String userName;

    @Temporal(TemporalType.DATE)
    private Date joinedDate;
    private String Address;


    private String description;



    public Date getJoinedDate() {
        return joinedDate;
    }
    public void setJoinedDate(Date joinedDate) {
        this.joinedDate = joinedDate;
    }
    public String getAddress() {
        return Address;
    }
    public void setAddress(String address) {
        Address = address;
    }
    public String getDescription() {
        return description;
    }
    public void setDescription(String description) {
        this.description = description;
    }

    public int getUserId() {
        return userId;
    }
    public void setUserId(int userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName + "from Getter";
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
}

I am trying to save it in postgreSQL database. and the field userName is not saving.

Answer 1

Since userName is static, it doesn't belong to an instance, it belongs to the class itsself. That's what static means.

Answer 2

According to docs:

If the entity class uses persistent fields, the Persistence runtime accesses entity-class instance variables directly. All fields not annotated javax.persistence.Transient or not marked as Java transient will be persisted to the data store. The object/relational mapping annotations must be applied to the instance variables.

Since userName is static, it won't be persisted.

Persistent fields and properties