JPA entity with @Entity annotation in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the @Entity annotation do in a Spring Boot application?

The @Entity annotation marks a class as a JPA entity, meaning it represents a table in the database. It tells Spring Boot and JPA to manage this class for database operations.

beginner

Which annotation is required to specify the primary key in a JPA entity?

The @Id annotation is used to mark a field as the primary key of the entity. This field uniquely identifies each record in the database table.

intermediate

Why should a JPA entity class have a no-argument constructor?

JPA requires a no-argument constructor so it can create instances of the entity using reflection. This constructor can be public or protected.

intermediate

What is the default table name for a JPA entity if @Table annotation is not used?

If @Table is not specified, the default table name is the same as the entity class name, usually case-sensitive depending on the database.

beginner

How do you map a simple Java class to a database table using JPA?

You add the @Entity annotation to the class, mark a field with @Id for the primary key, and optionally use @Column to customize column mapping.

What annotation marks a class as a JPA entity?

A @Entity

B @Table

C @Component

D @Repository

The @Entity annotation tells JPA that the class is an entity representing a database table.

Which annotation identifies the primary key field in a JPA entity?

A @PrimaryKey

B @Id

C @Key

D @Column

The @Id annotation marks the primary key field in a JPA entity.

What happens if a JPA entity class does not have a no-argument constructor?

A JPA will create the entity anyway

B Compilation error

C The entity will be ignored

D Runtime error when JPA tries to instantiate the entity

JPA uses reflection to create entity instances and requires a no-argument constructor; otherwise, it throws a runtime error.

If you don't specify @Table, what table name does JPA use?

A The package name

B The database default

C The class name

D No table is created

By default, JPA uses the entity class name as the table name.

Which annotation customizes the column name in a JPA entity?

A @Column

B @Table

C @Entity

D @Id

@Column lets you specify the column name and other properties for a field in the database.

Explain how to create a simple JPA entity class using @Entity and @Id annotations.

Think about how the class maps to a database table and how JPA identifies each record.

Describe why the no-argument constructor is important in a JPA entity.

Consider how JPA creates objects behind the scenes.