How do you use CascadeType in JPA?

Table of Contents

• Introduction
• Cascade Types in JPA
  • 1. CascadeType.PERSIST
    • Example:
  • 2. CascadeType.MERGE
    • Example:
  • 3. CascadeType.REMOVE
    • Example:
  • 4. CascadeType.REFRESH
    • Example:
  • 5. CascadeType.ALL
    • Example:
• Practical Examples
  • Example 1: Saving an Order with Items
  • Example 2: Deleting a Department and Its Employees
• Conclusion

Introduction

In Java Persistence API (JPA), CascadeType is used to define how operations on an entity should be propagated to its associated entities. This is especially useful when working with entity relationships like one-to-many, many-to-one, or many-to-many. By applying cascade types, you can ensure that certain operations on parent entities automatically propagate to related entities, streamlining your code and ensuring consistency.

In this guide, we’ll explain how to use CascadeType in JPA and provide practical examples of common use cases.

Cascade Types in JPA

1. CascadeType.PERSIST

The PERSIST cascade type allows the persistence context to propagate the persist() operation from a parent entity to its associated entities. When a parent entity is persisted (saved to the database), the associated child entities are also persisted.

Example:

In this example, when an Order entity is persisted, the associated Item entities are also automatically persisted due to the CascadeType.PERSIST.

2. CascadeType.MERGE

The MERGE cascade type is used to propagate the merge() operation. If the parent entity is merged, any associated entities that are in the persistence context will also be merged.

Example:

Here, when an Author entity is merged (updated), the associated Book entities will also be merged if they are modified.

3. CascadeType.REMOVE

The REMOVE cascade type allows you to propagate the remove() operation to associated entities. If the parent entity is removed, the child entities will also be deleted automatically.

Example:

In this example, if a Department entity is removed, all associated Employee entities will also be removed from the database.

4. CascadeType.REFRESH

The REFRESH cascade type propagates the refresh() operation, which reloads the state of the entity from the database. When applied, it ensures that the associated entities also have their state refreshed.

Example:

If a Customer entity is refreshed, the Order entities associated with it will also be refreshed from the database.

5. CascadeType.ALL

The ALL cascade type is a combination of all the other cascade types (PERSIST, MERGE, REMOVE, REFRESH, and DETACH). This means that all operations applied to the parent entity will also be applied to its associated entities.

Example:

With CascadeType.ALL, all operations (persist, merge, remove, etc.) on the Library entity will be propagated to the Book entities.

Practical Examples

Example 1: Saving an Order with Items

Example 2: Deleting a Department and Its Employees

Conclusion

Using CascadeType in JPA helps manage entity relationships and ensures that operations on parent entities are propagated to their associated entities automatically. By choosing the right cascade type, you can streamline your code and maintain consistency between related entities. Always remember to choose the appropriate cascade type for each relationship to avoid unintended side effects, especially when dealing with sensitive operations like removing entities.