Our application uses PagingAndSortingRepository to serve our REST API. This works great, but we ran into a specific edge case that we can't seem to solve:
We have a alphanumeric field that has to be sortable (e.g. SOMETHING-123). One possible solution was to use something like a regex inside the database query's order by. This was ruled out, as we wanted to stay database independant. Thus we split up the column into two columns.
So before we had an Entity with 1 String field:
#Entity
public class TestingEntity {
#Id
#GeneratedValue
private long id;
private String alphanumeric
}
And now we have an Entity with 2 additional fields and the old field made #Transient which is filled at #PostLoad:
#Entity
public class Testing {
#Id
#GeneratedValue
private long id;
#Transient
public String alphanumeric;
#PostLoad
public void postLoad(){
this.alphanumeric = this.alphabetic + "-" + this.numeric;
}
public void setAlphanumeric(String alphanumeric) {
int index = alphanumeric.indexOf("-");
this.alphabetic = alphanumeric.substring(0, index);
this.numeric = Long.parseLong(alphanumeric.substring(index + 1));
}
#JsonIgnore
private String alphabetic;
#JsonIgnore
private Long numeric;
}
This is working great and the additional fields do not get exposed. However the sorting on the field "alphanumeric" does obviously not work anymore. The simplest solution would be to make this request:
localhost:8080/api/testingEntity?sort=alphanumeric,asc
and internally rewrite it to the working request:
localhost:8080/api/testingEntity?sort=alphabetic,asc&sort=numeric,asc
What is the best way to tackle this issue?
Related
I'd like to find all Offer documents by Offer.ProductProperties.brand:
#Document(collection = "offers")
public class Offer {
#Id
private String id;
#NotNull
#DBRef
private ProductProperties properties;
ProductProperties:
#Document(collection = "product_properties")
public class ProductProperties {
#Id
private String id;
#NotNull
#NotEmpty
private String brand;
Service:
Flux<ProductProperties> all = productPropertiesRepository.findAllByBrand(brand);
List<String> productPropIds = all.toStream()
.map(ProductProperties::getId)
.collect(Collectors.toList());
Flux<Offer> byProperties = offerRepository.findAllByProperties_Id(productPropIds);
But unfortunately byProperties is empty. Why?
My repository:
public interface OfferRepository extends ReactiveMongoRepository<Offer, String> {
Flux<Offer> findAllByProperties_Id(List<String> productPropertiesIds);
}
How to find all Offers by ProductProperties.brand?
Thanks!
After reading some documentation found out that You cannot query with #DBRef. Hence the message
Invalid path reference properties.brand! Associations can only be
pointed to directly or via their id property
If you remove DBRef from the field, you should be able to query by findAllByProperties_BrandAndProperties_Capacity.
So the only ways is how you are doing. i.e. Fetch id's and query by id.
As I said in the comment, the reason it is not working is because return type of findAllByProperties_Id is a Flux. So unless u execute a terminal operation, you wont have any result. Try
byProperties.collectList().block()
As Spring jpa Provides some usefull features to find Items from a repository by defining it in the method name. e .x findByTitle(String title) then Spring is automatically searching the Title Colum for the given String. If i have an int column named numberOfCopies and i want only to find the datasets with >0 greater then null how would define such a method ?
to filter out those books with the numberOfCopies equals 0 = zero
#Entity
public class Book {
#Id
private int id;
private String title;
private int numberOfCopies;
}
can i use the Repomethod
public List findBooksByNumberOfCopies.greater then 0 ?To Use this Spring Feature without some if or for loops
First, you should use Integer, since it is better, in my opinion, to use wrapper classes than to primitives, and enforce not null requirement through annotations, e.g. #Column(nullable = false)
#Entity
public class Book {
#Id
private Integer id;
private String title;
private Integer numberOfCopies;
}
Then you can add the following two methods in your BookRepository;
List<Book> findByNumberOfCopiesGreaterThan(Integer numberOfCopies);
default List<Book> findAllAvailableBooks() {
return findByNumberOfCopiesGreaterThan(0);
}
and use the default findAllAvailableBooks method, with hardcoded 0 value which is your requirement.
you can easily use
List<Book> findByNumberOfCopiesGreaterThanEqual(int numberOfCopies);
Pretty sure this would work:
public interface BookRepo extends JpaRepository<Book, Integer> {
#Query("SELECT b FROM Book b WHERE b.numberOfCopies >= 0")
public Optional<List<Book>> getTheBooksWithMultCopies();
}
// back in your component class:
{
...
Optional<List<Book>> optionalBookList = myBookRepo.getTheBooksWithMultCopies();
if (optionalBookList.isPresent()){
List<Book> bookList = optionalBookList.get();
}
}
Note that the language within the query is called HQL, which is what is used by Hibernate internally (which is used by JPA internally). It's really not very intimidating - just, know that you the objects in your POJO, which map to your database table, rather than your database table directly.
Also, I'd recommend using Integer over int in entity classes, at least if your value is nullable. Otherwise, numberOfCopies will always default to 0, which may not be desirable and may cause exceptions that are difficult to decipher.
GreaterThanEqual takes an Integer not int
List<Book> findByNumberOfCopiesGreaterThanEqual(Integer numberOfCopies);
I get an Post request that would give me a List<PersonApi> Objects
class PersonApi {
private String name;
private String age;
private String pincode ;
}
And I have an Entity Object named Person
#Entity
#Table(name = "person_master")
public class Person{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
Long id;
#Column(name = "name")
String name;
#Column(name = "age")
String age;
#Column(name = "pincode ")
String pincode ;
}
My record from Post request would look something like this (pseudocode representation of the data below)
[
"Arun","33","09876gh"
"James","34","8765468"
]
I need to do a bulk-validation using Spring JPA.. Give the List<PersonApi> and get a True or False based on the condition that all the entries in the PersonApi objects list should be there in the database.
How to do this ?
The selected answer is not a right one. (not always right)
You are selecting the whole database to check for existence. Unless your use case is very special, i.e. table is very small, this will kill the performance.
The proper way may start from issuing repository.existsById(id) for each Person, if you never delete the persons, you can even apply some caching on top of it.
exists
Pseudo Code:
List<PersonApi> personsApiList = ...; //from request
List<Person> result = personRepository.findAll();
in your service class you can access your repository to fetch all database entities and check if your list of personapi's is completeley available.
boolean allEntriesExist = result.stream().allMatch(person -> personsApiList.contains(createPersonApiFromPerson(person)));
public PersonApi createPersonApiFromPerson(Person person){
return new PersonApi(person.getName(), person.getAge(), person.getPincode());
}
I have the following two resources, and their association;
#Table(name = "Item")
#Data
#Entity
public class Item {
#ManyToOne
#JoinColumn(name = "fk_wrapper")
private Wrapper wrapper;
#Id
#GeneratedValue
private String id;
private Integer someValue;
}
and;
#Table(name = "Wrapper")
#Data
#Entity
public class Wrapper {
#Id
#GeneratedValue
private String id;
#OneToMany(cascade = CascadeType.ALL)
#JoinColumn(name = "fk_wrapper")
private List<Item> items;
private String someField;
}
Then, first, I create a Wrapper;
POST http://localhost:8080/wrappers/
{
"someField": "asd"
}
http://localhost:8080/wrappers/1 created, then I create two Item's, linked to this Wrapper;
POST http://localhost:8080/items/
{
"someValue": "5",
"wrapper": "http://localhost:8080/wrappers/1"
}
&
POST http://localhost:8080/items/
{
"someValue": "7",
"wrapper": "http://localhost:8080/wrappers/1"
}
After all this, when I call the endpoint http://localhost:8080/wrappers/1/items, I get the list of these two items, as expected, but what the trouble is that, I cannot seem to have a sorting feature on this endpoint. I seem to be able to sort in http://localhost:8080/items endpoint, but while fetching with association, there doesn't seem to be a sorting feature. Is this lack of sorting is intended, or am I lacking some configuration?
P.S. when I create a custom search method, for example;
#RepositoryRestResource
public interface ItemRepository extends JpaRepository<Item, String> {
List<Item> findByWrapper_Id(#Param("id") String id, Sort sort);
}
Then I can use the sorting with http://localhost:8080/items/search/findByWrapper_Id endpoint, but too ugly imo, considering there is already an auto-generated endpoint.
Spring Data Rest doesn't support sorting on the associations.
You seem to have already found the best way to do what you need, according to the Spring Data Rest team - create a query for fetching the data you need. That will indeed support both pagination and sorting.
The reason why it's not supported has to do with the time when the queries are made to fetch the main resource (before the association endpoints are built) and the facts that the association endpoint makes use of the the loaded entity associations directly and that for supporting sort, a new query would need to be made anyway.
More detailed information can be found here:
https://jira.spring.io/browse/DATAREST-725?focusedCommentId=122244&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-122244
Cheers!
I have some problem with Morphia.
Could someone help me?
I am writing web-project on Spring + MongoDB about movies and celebrities.
I have entity class Genre:
#Entity(value="genres")
public class Genre implements IGenre {
#Id
#Indexed
private ObjectId id;
#Indexed
private String name;
private String description;
private long quantity;
private Set <IMovie> movies;
//getters and setters
}
And entity class Movie:
#Entity(value="movies")
public class Movie implements IMovie {
#Id
#Indexed
private ObjectId id;
#Indexed
private String originalTitle;
private String year;
private Set <IGenre> genres;
// getters and setters
}
I have 30 genres. And for example one of them: Comedy.
Also I have 250 000 comedies.
And now I want to do movie pagination by genre = comedy.
How I can get only 20 records from all comedies.
If I use #Embedded or #Reference annotation I will still get the entire list at once. And it's to big for use it in controllers.
You should change your data schema for doing such a query. The schema you use has a circular dependency, in your Genre entity you are holding Movies entity and in movies you hold Genre. Also holding all of the movies according to genre is not easy to query. If I were you I would use such a schema.
#Entity(noClassnameStored = true) // you wouldn't have any problem when you change the class name or package of your class if you don't store the classname through this annotation
public class Movie implements IMovie {
#Id
#Indexed
private ObjectId id;
#Indexed
private String originalTitle;
private String year;
private Set <String> genres; // unique identifier of the genres instead of embedding the whole genre entity
// getters and setters
}
So having such a schema, you can retrieve the movies having a particular genre by writing a simple $in query through genres field. Example query for your case:
datastore.find(Movie.class).field("genres").in(Lists.newArrayList("comedy")).limit(20).asList;
In the below web-page of mongo you can find suggestions about how to design your schema according to diffrerent scenarios.
http://docs.mongodb.org/manual/core/data-modeling/#data-modeling-patterns-and-examples
I'm not too familiar with Mongo, but it looks like you would need to implement a custom query here. Whatever you do, you need to pass a start for your page, as well as a page size (20 in your case).
You can do pagination in Morphia by combining .offset(page_start) and .limit(page_size) on a query. So first you would create a query to get movies that belong to a certain genre, and then apply the pagination.
Looks like it is handled using repositories in Spring http://static.springsource.org/spring-data/data-mongodb/docs/1.0.0.RELEASE/reference/html/#repositories.special-parameters
You'd use a Pageable implementation to pass paging data, without worrying about doing the offset and limit calls yourself. There's an example of "Web pagination" further in the doc.
Hope this helps!