34-Spring Boot - Spring Data

Question 1

What is the starter for Spring JPA?

Answer 1

spring-boot-starter-data-jpa

Question 2

What jars are inside Spring JPA?

Answer 2

1. spring-boot-starter.jar
2. spring-boot-starter-jdbc.jar
3. spring-boot-starter-aop.jar
4. spring-data-jpa.jar
5. hibernate-core.jar
6. javax.transaction-api

Question 3

What happens if Spring boot found JPA on the classpath?

Answer 3

It will auto-configure:

1. DataSource
2. LocalContainerEntityManagerFactoryBean
3. JpaTransactionManager

Question 4

How to customize EntityManager?

Answer 4

Configure the bean LocalContainerEntityManagerFactoryBean and set:

1. JpaVendorAdapter e.g. HibernateJpaVendorAdapter
2. JpaProperties e.g. hibernate.format_sql
3. Datasource
4. PackagesToScan

Question 5

What is the purpose of @EnableAutoConfiguration? Does it belong to spring framework or spring boot?

Answer 5

1. Enable auto-configuration of the Spring Application Context, attempting to guess and configure beans that you are likely to need.
   Auto-configuration classes are usually applied based on your classpath and what beans you have defined
2. Part of Spring Boot

Question 6

What beans will be scanned with @EnableAutoConfiguration?

Answer 6

1. Package of the config class annotated with @EnableAutoConfiguration
2. All sub-packages

Question 7

In Spring Boot, how to customize the packages that will be scanned for entities?

Answer 7

Using @EntityScan e.g.
@SpringBootApplication
@EntityScan(“my.package”)
public class Application {}

Question 8

Spring JPA: how to customize DB name?

Answer 8

spring.jpa.database=my-db-name

Question 9

Spring JPA: how to disable the feature that creates tables automatically?

Answer 9

spring.jpa.hibernate.ddl-auto=none

Question 10

What are options for spring.jpa.hibernate.ddl-auto? What is the default one?

Answer 10

none
validate
update
create
create-drop (default)

Question 11

How to show SQL queries in a nice format?

Answer 11

spring. jpa.show-sql=true

spring. jpa.properties.hibernate.format_sql=true

Question 12

How to set a custom property for Hibernate?

Answer 12

spring.jpa.properties.hibernate.xxx=…

Question 13

What ORMs does Spring support?

Answer 13

Hibernate only

Question 14

What are the benefits of using Spring data?

Answer 14

1. Reduce boilerplate code for data access

2. Works in many environments

Question 15

List out 6 sub-projects of Spring Data

Answer 15

1. JPA
2. MongoDB
3. Redis
4. Neo4j
5. Hadoop
6. Solr

Question 16

Motivation for Spring Data

Answer 16

1. Provide similar support for NoSQL databases that Spring does for RDBMS
   a. Template classes to hide low-level
   b. Common data-access exceptions
   c. Portability of the code over different storage technologies
2. It implements repositories for you

Question 17

How to define a repository?

Answer 17

1. Annotate domain class with @Entity, (optional: @Table, @Id, @GeneratedValue)
2. Define your repository as an interface

Question 18

What interfaces will be scanned for repositories?

Answer 18

Interfaces that extend Repository or CrudRepository

Question 19

How to define an auto-increment id?

Answer 19

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

Question 20

What is the annotation for domain class in MongoDB and Neo4j, Gemfire?

Answer 20

@Document - MongoDb
@NodeEntity - Neo4J
@Region - Gemfire

Question 21

List out methods in Repository

Answer 21

It’s empty

Question 22

List out 5 methods in CrudRepository

Answer 22

1. save(T): T
2. saveAll(Iterable): Iterable
3. findById(ID), existsById(ID), findAll(): Iterable, findAllById(Iterable)
4. delete(T), deleteById(ID), deleteAll(Iterable)
5. count()

Question 23

Describe PagingAndSortingRepository

Answer 23

1. Extend CrudRepository
2. Add 2 more methods:
   Iterable findAll(Sort)
   Page findAll(Pageable)

Question 24

Ways to implement the method to get the first 10 records?

Answer 24

1. findFirst10ByField(field)

2. findTop10ByField(field)

Question 25

List out repository query subject keywords

Answer 25

1. (find or read or get or search or stream)…By
   optional: DomainType e.g. findUserBy… = findBy
2. exists…By
3. count…By
4. (remove or delete)…By
5. …(First or Top)…
6. …Distinct…

Question 26

List out 6 repository query predicate keywords

Answer 26

1. And, Or
2. Between, IsBetween
3. False, IsFalse
4. GreaterThan, IsGreaterThan
5. NotNull, IsNotNull
6. Is, Equals, (or no keyword)
   Notice that most of the operators support 2 forms:
   and Is e.g. In, IsIn
   Read more here: https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#repository-query-keywords

Question 27

List out repository query predicate modifier keywords

Answer 27

1. IgnoreCase, IgnoringCase
2. AllIgnoreCase, AllIgnoringCase
3. OrderBy

Question 28

Create a repository method to search Users by username and email, return data should be sorted by FirstName ascending then LastName descending

Answer 28

findByUsernameAndEmailOrderByFirstNameAscLastNameDesc(String username, String email)
Notice that there’s no And after FirstNameAsc

Question 29

How to control repositories scanner manually?

Answer 29

@Configuration

@EnableJpaRepository(basePackages=”my.package”)

Question 30

Describe JpaRepository

Answer 30

1. extends PagingAndSortingRepository
2. Provide flush(), saveAndFlush(T entity)
3. deleteInBatch, deleteAllInBatch
4. getOne(ID): access a lazy-loading reference

Question 31

How to create a custom repository method?

Answer 31

1. Create a repository extends an automatic repository e.g.
interface CustomerRepository extends Repository {
    User customMethod();
}
2. Option 1: Implement with the class name: CustomerRepositoryImpl (Spring will search for postfix Impl), no need to mark with annotation
Option 2: Implement with any class name then create a bean with the name "CustomerRepositoryImpl"

Question 32

What is the result of MyRepository.findById(id) if not found?

Answer 32

null

Question 33

How to make MyRepository.findById(id) return optional object?

Answer 33

Declare the return type with Optional: Optional findById(id)

Question 34

How to customize the custom repository scanning (e.g. scan for CustomCustomerRepository implementation)?

Answer 34

@Configuration
@EnableJpaRepository(repositoryImplementationPostFix=”Manager”)
default is: “Impl”

Question 35

When will the test with @SpringBootTest scan for a @SpringBootConfiguration?

Answer 35

When:

1. there is no nested @Configuration
2. no explicit classes are specified (e.g. @SpringBootTest(classes = RewardsConfig.class))

Question 36

Which of the following implementations of PlatformTransactionManager can be used with EclipseLink JPA?

Answer 36

JpaTransactionManager

JtaTransactionManager