Spring Data

Question 1

What built-in class does Spring provide that implements Pageable?

Answer 1

PageRequest

Question 2

Spring Data

What is the signature for a “derived query method”?

Answer 2

[Subject Keyword][(Optional Description]By[Predicate]

[Subject Keyword] could be:

1. Find
2. Exists
3. Count
4. Delete

[Optional Description] could be:

1. First<number>
2. Distinct

[Predicate] is composed of:

1. Class Property
2. Logical keywords

Question 3

What annotation can be used on the main configuration class to scan for domain objects defined outside of its directory or sub-directories?

Answer 3

@EntityScan(basePackages=String[])

Question 4

What is Spring Data?

Answer 4

Spring Data is a framework for building data access applications

Question 5

What is a repository?

Answer 5

A repository is a data access object. It’s used to interface with a database

Question 6

What is a datasource/connection string?

Answer 6

A datasource is all the information an application needs to connect to a database

Question 7

How can you make a repository method implement a native query?

Answer 7

Annotate the query method with @Query

Question 8

What annotation on the main configuration class can be used to scan for repositories outside of its package?

Answer 8

@EnableMongoRepositories(basePackages=String[])

Question 9

What are the 2 steps to implement custom repositories?

Answer 9

1. Define a custom interface and implementation
2. Define a normal repository interface that extends both a Spring repository and the custom interface

Question 10

What is the relationship between @EnableAutoConfiguration and @Document?

Answer 10

@Document will be scanned for by the configuration class that is annotated with @EnableAutoConfiguration (@SpringBootApplication)

Question 11

What is the difference between Page and Slice?

Answer 11

A Page knows about the total number of elements and pages available. It does so by the infrastructure triggering a count query to calculate the overall number. As this might be expensive (depending on the store used), you can instead return a Slice. A Slice knows only about whether a next Slice is available, which might be sufficient when walking through a larger result set

Question 12

Do “query derived methods” support the use of parameters that are mapped to @DBRef fields in the domain class?

Answer 12

No

Question 13

Can a “derived query method” be used to update a document?

Answer 13

Yes. For example:

@Update("{ '$set' : { 'password' : ?1 } }")
void findAndSetPasswordByEmail(String email, String password);

Question 14

True or False

“Derived query methods” annotated with @Update must return either void or a numeric type

Answer 14

True

Question 15

What is the difference between @DBRef and @DocumentReference?

Question 16

True or False

@Document
public class Account {

  @Id
  private ObjectId id;
  private Float total;
}

@Document
public class Person {

  @Id
  private ObjectId id;
  @Indexed
  private Integer ssn;
  @DBRef
  private List<Account> accounts;
}

The mapping framework does not handle cascading saves. If you change an Account object that is referenced by a Person object, you must save the Account object separately. Calling save on the Person object does not automatically save the Account objects in the accounts property

Answer 16

True

Question 17

What is the n + 1 problem?

Answer 17

The n + 1 problem is a data retrieval problem. It occurs when a query returns a list of resources (n), and for each resource, an additional query (1) is made. DTO projections, caching, etc. can help avoid n + 1 problems