CRUD methods (save, findById, findAll, delete) in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the save method do in Spring Boot's CRUD repository?

The save method adds a new entity or updates an existing one in the database. It returns the saved entity with any generated values like IDs.

beginner

How does findById work in Spring Boot repositories?

It looks for an entity by its unique ID. It returns an Optional that contains the entity if found, or is empty if not found.

beginner

What is the purpose of findAll in Spring Boot CRUD repositories?

It retrieves all entities of a given type from the database and returns them as a list.

beginner

Explain what delete does in Spring Boot CRUD repositories.

The delete method removes an entity from the database. You can delete by passing the entity or by its ID using deleteById.

intermediate

Why is Optional used with findById in Spring Boot?

Optional helps safely handle the case when an entity might not exist. It avoids errors by forcing you to check if the entity is present before using it.

Which CRUD method in Spring Boot is used to add or update an entity?

A save

B findById

C findAll

D delete

The save method adds a new entity or updates an existing one.

What does findById return if no entity is found?

A An empty Optional

B An empty list

C An exception

D null

findById returns an empty Optional if the entity is not found.

Which method retrieves all entities from the database?

A save

B findAll

C delete

D findById

findAll returns a list of all entities.

How can you delete an entity using Spring Boot CRUD repository?

A Only by entity ID

B Only by entity object

C By calling save with null

D By entity object or ID

You can delete by passing either the entity object or its ID.

Why is it good to use Optional with findById?

A To automatically delete missing entities

B To speed up queries

C To avoid null pointer errors

D To return multiple entities

Optional helps avoid null pointer errors by forcing checks for presence.

Describe how the save, findById, findAll, and delete methods work in Spring Boot CRUD repositories.

Think about how you add, find, list, and remove items in a real collection.

Explain why Optional is useful when using findById in Spring Boot.

Consider what happens if you look for something that might not be there.