How to Clone a JPA Entity in Java

What is the best way to clone a JPA entity while modifying its fields?

@Entity
public class YourEntity {
    @Id
    private Long id;
    private String field;
    // other fields, getters and setters
}

Cloning a JPA entity involves creating a duplicate of an object that has been persisted in the database, while ensuring that the new object has a different identifier and may have modified fields. Here’s how to effectively clone a JPA entity in Java.

public YourEntity clone() {
    YourEntity cloned = new YourEntity();
    cloned.setField(this.field);
    // Copy other fields as needed
    return cloned;
}

Causes

• Preserving the integrity of the JPA entity during the cloning process.
• Ensuring that the cloned entity does not retain the same database identifier as the original entity.

Solutions

• Set the @Id field of the original entity to null before persisting the cloned entity to generate a new unique identifier automatically.
• Implement a clone method within the entity class to manage which fields to copy and which to modify during the cloning process.
• Utilize a cloning framework like Apache Commons Lang or Dozer to simplify the cloning process without manual copying.

Mistake: Directly cloning the entity without nullifying the ID field.

Solution: Always ensure the ID field is set to null to avoid duplicate key exceptions.

Mistake: Not copying necessary fields when implementing a clone method.

Solution: Review all entity fields carefully to ensure proper cloning behavior.