Why relationships matter in JPA in Spring Boot - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a one-to-many relationship in JPA.

Spring Boot

@Entity
public class Author {
    @Id
    private Long id;
    
    @OneToMany(mappedBy = [1])
    private List<Book> books;
}

Drag options to blanks, or click blank then click option'

Aauthor

BauthorId

Cbooks

Dbook

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong field name in mappedBy causes errors.

Confusing the collection name with the mappedBy value.

The mappedBy attribute refers to the field name in the related entity that owns the relationship. Here, it should be author as defined in the Book entity.

2fill in blank

medium

Complete the code to specify the owning side of a many-to-one relationship.

Spring Boot

@Entity
public class Book {
    @Id
    private Long id;

    @ManyToOne
    @JoinColumn(name = [1])
    private Author author;
}

Drag options to blanks, or click blank then click option'

A"book_id"

B"id"

C"author_id"

D"authorName"

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong column name causes database errors.

Omitting quotes around the column name.

The @JoinColumn specifies the foreign key column in the Book table that links to the Author. It is commonly named author_id.

3fill in blank

hard

Fix the error in the code to correctly define a bidirectional one-to-one relationship.

Spring Boot

@Entity
public class User {
    @Id
    private Long id;

    @OneToOne(mappedBy = [1])
    private Profile profile;
}

@Entity
public class Profile {
    @Id
    private Long id;

    @OneToOne
    @JoinColumn(name = "user_id")
    private User user;
}

Drag options to blanks, or click blank then click option'

Auser

BprofileId

Cprofile

DuserId

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong field name in mappedBy causes runtime errors.

Confusing the owning and inverse sides.

The mappedBy in User should refer to the field name in Profile that owns the relationship, which is user.

4fill in blank

hard

Fill both blanks to create a many-to-many relationship with a join table.

Spring Boot

@Entity
public class Student {
    @Id
    private Long id;

    @ManyToMany
    @JoinTable(name = [1],
        joinColumns = @JoinColumn(name = [2]))
    private Set<Course> courses;
}

Drag options to blanks, or click blank then click option'

A"student_course"

B"student_id"

C"course_id"

D"course_student"

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up join table and join column names.

Using the wrong entity name in joinColumns.

The join table is commonly named combining both entities, e.g., student_course. The joinColumns refers to the foreign key column for the owning entity, here student_id.

5fill in blank

hard

Fill all three blanks to define a unidirectional one-to-many relationship with cascade and fetch type.

Spring Boot

@Entity
public class Department {
    @Id
    private Long id;

    @OneToMany(cascade = [1], fetch = [2])
    @JoinColumn(name = [3])
    private List<Employee> employees;
}

Drag options to blanks, or click blank then click option'

ACascadeType.ALL

BFetchType.LAZY

C"department_id"

DFetchType.EAGER

Attempts:

3 left

💡 Hint

Common Mistakes

Using FetchType.EAGER can cause performance issues.

Forgetting to specify the join column name.

CascadeType.ALL applies all cascade operations. FetchType.LAZY delays loading employees until needed. The join column department_id links employees to the department.