Quiz: Database Configuration

Test your knowledge on PostgreSQL, Hibernate, and Lombok.

30 questions - Click on each question to reveal the answer.

Questions 1-10: PostgreSQL

Question 1: How to add PostgreSQL to a Spring Boot project?

Answer:

<dependency>
    <groupId>org.postgresql</groupId>
    <artifactId>postgresql</artifactId>
    <scope>runtime</scope>
</dependency>

Question 2: How to configure the PostgreSQL connection?

Answer:

spring:
  datasource:
    url: jdbc:postgresql://localhost:5432/mydb
    username: postgres
    password: secret
    driver-class-name: org.postgresql.Driver

Question 3: How to run PostgreSQL with Docker?

Answer:

docker run -d \
  --name postgres \
  -e POSTGRES_DB=mydb \
  -e POSTGRES_USER=postgres \
  -e POSTGRES_PASSWORD=secret \
  -p 5432:5432 \
  postgres:15

Question 4: What is the difference between H2 and PostgreSQL?

Answer:

H2	PostgreSQL
In-memory (default)	Persistent
Development/Testing	Production
No installation	Installation required
Data lost on restart	Persistent data
Lightweight	Full-featured and robust

Question 5: How to configure the connection pool?

Answer: Spring Boot uses HikariCP by default:

spring:
  datasource:
    hikari:
      maximum-pool-size: 10
      minimum-idle: 5
      connection-timeout: 30000
      idle-timeout: 600000
      max-lifetime: 1800000

Question 6: How to set a default schema?

Answer:

spring:
  jpa:
    properties:
      hibernate:
        default_schema: my_schema

Or in the URL:

url: jdbc:postgresql://localhost:5432/mydb?currentSchema=my_schema

Question 7: How to handle TimeZones with PostgreSQL?

Answer:

spring:
  jpa:
    properties:
      hibernate:
        jdbc:
          time_zone: UTC

Recommended: store in UTC, convert on display.

Question 8: How to configure SSL for PostgreSQL?

Answer:

spring:
  datasource:
    url: jdbc:postgresql://host:5432/db?ssl=true&sslmode=require

Modes: disable, allow, prefer, require, verify-ca, verify-full

Question 9: How to create a database with Docker Compose?

Answer:

# docker-compose.yml
services:
  db:
    image: postgres:15
    environment:
      POSTGRES_DB: mydb
      POSTGRES_USER: user
      POSTGRES_PASSWORD: pass
    volumes:
      - postgres-data:/var/lib/postgresql/data
      - ./init.sql:/docker-entrypoint-initdb.d/init.sql
    ports:
      - "5432:5432"

volumes:
  postgres-data:

Question 10: How to externalize database credentials?

Answer:

spring:
  datasource:
    url: ${DB_URL}
    username: ${DB_USER}
    password: ${DB_PASSWORD}

Set environment variables:

export DB_URL=jdbc:postgresql://localhost/mydb
export DB_USER=postgres
export DB_PASSWORD=secret

Questions 11-20: Hibernate DDL

Question 11: What is hibernate.ddl-auto?

Answer: Property that controls automatic schema generation:

Value	Behavior
`none`	No action
`validate`	Validates the schema
`update`	Updates the schema
`create`	Creates the schema (drop before)
`create-drop`	Creates and drops on shutdown

Question 12: Which value to use in production?

Answer: none or validate

spring:
  jpa:
    hibernate:
      ddl-auto: validate

In production, use migration tools (Flyway, Liquibase).

Question 13: How does Hibernate generate table names?

Answer: Default strategy: camelCase to snake_case

@Entity
public class UserProfile { }
// Table: user_profile

Customize:

spring:
  jpa:
    hibernate:
      naming:
        physical-strategy: org.hibernate.boot.model.naming.PhysicalNamingStrategyStandardImpl

Question 14: How to specify a table name?

Answer:

@Entity
@Table(name = "utilisateurs")
public class User {
    // ...
}

Question 15: How to specify a column name?

Answer:

@Entity
public class User {
    
    @Column(name = "nom_complet")
    private String fullName;
    
    @Column(name = "courriel", unique = true, nullable = false)
    private String email;
}

Question 16: How to define an auto-generated primary key?

Answer:

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

// Strategies:
// IDENTITY: DB auto-increment
// SEQUENCE: DB sequence
// TABLE: sequence table
// AUTO: automatic choice

Question 17: How to define a unique constraint?

Answer:

// On a column
@Column(unique = true)
private String email;

// On multiple columns
@Table(uniqueConstraints = {
    @UniqueConstraint(columnNames = {"firstName", "lastName"})
})
public class User { }

Question 18: How to define an index?

Answer:

@Entity
@Table(indexes = {
    @Index(name = "idx_email", columnList = "email"),
    @Index(name = "idx_name", columnList = "lastName, firstName")
})
public class User { }

Question 19: How to see the SQL generated by Hibernate?

Answer:

spring:
  jpa:
    show-sql: true
    properties:
      hibernate:
        format_sql: true

logging:
  level:
    org.hibernate.SQL: DEBUG
    org.hibernate.orm.jdbc.bind: TRACE

Question 20: How to validate the schema on startup?

Answer:

spring:
  jpa:
    hibernate:
      ddl-auto: validate

The application fails to start if the schema does not match the entities.

Questions 21-30: Lombok

Question 21: What is Lombok?

Answer: Library that generates repetitive code via annotations:

Getters/Setters
Constructors
equals/hashCode
toString
Builder

Significantly reduces boilerplate.

Question 22: How to add Lombok?

Answer:

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <scope>provided</scope>
</dependency>

Also install the IDE plugin (IntelliJ, Eclipse).

Question 23: How to generate getters and setters?

Answer:

@Getter
@Setter
public class User {
    private Long id;
    private String name;
}

// Generates:
// getId(), setId()
// getName(), setName()

Question 24: What is @Data?

Answer: Combines several annotations:

@Data  // = @Getter + @Setter + @ToString + @EqualsAndHashCode + @RequiredArgsConstructor
public class User {
    private Long id;
    private String name;
}

Question 25: How to create a builder?

Answer:

@Builder
public class User {
    private Long id;
    private String name;
    private String email;
}

// Usage:
User user = User.builder()
    .name("John")
    .email("john@example.com")
    .build();

Question 26: How to generate constructors?

Answer:

@NoArgsConstructor  // Empty constructor
@AllArgsConstructor // All fields
@RequiredArgsConstructor // Final and @NonNull fields
public class User {
    private final Long id;
    @NonNull
    private String name;
    private String email;
}

Question 27: How to use @Slf4j for logging?

Answer:

@Slf4j
@Service
public class UserService {
    
    public void process() {
        log.info("Processing...");
        log.debug("Details: {}", data);
        log.error("Error occurred", exception);
    }
}

Generates: private static final Logger log = LoggerFactory.getLogger(UserService.class);

Question 28: How to exclude a field from toString?

Answer:

@ToString(exclude = "password")
public class User {
    private String email;
    private String password;  // Excluded from toString
}

// Or
@ToString.Exclude
private String password;

Question 29: How to exclude a field from equals/hashCode?

Answer:

@EqualsAndHashCode(exclude = "orders")
public class User {
    private Long id;
    private List<Order> orders;  // Excluded
}

// Or
@EqualsAndHashCode.Exclude
private List<Order> orders;

Question 30: What are the best practices with Lombok and JPA?

Answer:

Avoid @Data on entities (issues with lazy loading)
Exclude relationships from equals/hashCode
Use @ToString.Exclude for bidirectional relationships
Prefer @Getter and @Setter separately
Be cautious with @EqualsAndHashCode on entities

@Entity
@Getter
@Setter
@NoArgsConstructor
@ToString(exclude = "orders")
@EqualsAndHashCode(onlyExplicitlyIncluded = true)
public class User {
    
    @Id
    @EqualsAndHashCode.Include
    private Long id;
    
    @OneToMany(mappedBy = "user")
    private List<Order> orders;
}

Score

Score	Level
27-30	Excellent - Configuration mastered
21-26	Good - Some revisions needed
15-20	Average - Review the chapters
Less than 15	Needs improvement

Back to Module 4

Questions 1-10: PostgreSQL​

Questions 11-20: Hibernate DDL​

Questions 21-30: Lombok​

Score​

Questions 1-10: PostgreSQL

Questions 11-20: Hibernate DDL

Questions 21-30: Lombok

Score