Cascade Types in JPA

Cascade Types in JPA

Cascade types define the behavior of JPA relationships (e.g., one-to-many, many-to-one) concerning persistence operations. They specify whether operations performed on one entity should be cascaded to related entities. This simplifies the management of entity relationships and ensures data integrity.

Cascade Types in JPA :

CascadeType.ALL :

CascadeType.ALL indicates that all operations (persist, merge, remove, refresh) should be cascaded to the related entities. This means that if an operation is performed on an entity, such as persisting it, the same operation will also be applied to all related entities associated with it.

CascadeType.PERSIST :

CascadeType.PERSIST specifies that only the persist operation should be cascaded to related entities. This means that when an entity is persisted, all related entities will also be persisted automatically. However, operations like merge, remove, or refresh will not cascade to related entities.

Example in Java

Let’s demonstrate the difference between CascadeType.ALL and CascadeType.PERSIST with a Java example.

1. Parent Entity Class Definition
java
import javax.persistence.*;
import java.util.List;

@Entity
public class Department {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;

    @OneToMany(mappedBy = "department", cascade = CascadeType.ALL)
    private List<Employee> employees;

    // Getters and Setters
}

In this example, the Department class has a one-to-many relationship with Employee. The cascade = CascadeType.ALL attribute ensures that all operations (persist, merge, remove, refresh) performed on Department entities will cascade to related Employee entities. For example, if a Department is removed, all associated Employee entities will also be removed.

2. Child Entity Class Definition
java
import javax.persistence.*;

@Entity
public class Employee {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;

    @ManyToOne
    @JoinColumn(name = "department_id")
    private Department department;

    // Getters and Setters
}

The Employee class has a many-to-one relationship with Department. Each employee belongs to one department.

3. Using CascadeType.PERSIST
java
import javax.persistence.*;

@Entity
public class Department {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;

    @OneToMany(mappedBy = "department", cascade = CascadeType.PERSIST)
    private List<Employee> employees;

    // Getters and Setters
}

In this modified example, cascade = CascadeType.PERSIST specifies that only the persist operation should be cascaded to related Employee entities. Operations like merge, remove, or refresh will not cascade to Employee entities. If a Department is persisted, all associated Employee entities will also be persisted.