In Spring Data, we have PagingAndSortingRepository which inherits from CrudRepository. In reactive Spring Data, we only have
ReactiveSortingRepository which inherits from ReactiveCrudRepository.
How could we make pagination in a reactive way ?
Will we able to make this in future with ReactivePagingAndSortingRepository for instance?
Reactive Spring Data MongoDB repositories do not provide paging in the sense of paging how it's designed for imperative repositories. Imperative paging requires additional details while fetching a page. In particular:
The number of returned records for a paging query
Optionally, total count of records the query yields if the number of returned records is zero or matches the page size to calculate the overall number of pages
Both aspects do not fit to the notion of efficient, non-blocking resource usage. Waiting until all records are received (to determine the first chunk of paging details) would remove a huge part of the benefits you get by reactive data access. Additionally, executing a count query is rather expensive, and increases the lag until you're able to process data.
You can still fetch chunks of data yourself by passing a Pageable (PageRequest) to repository query methods:
interface ReactivePersonRepository extends Repository<Person, Long> {
Flux<Person> findByFirstnameOrderByLastname(String firstname, Pageable pageable);
}
Spring Data will apply pagination to the query by translating Pageable to LIMIT and OFFSET.
References:
Reference documentation: Reactive repository usage
import com.thepracticaldeveloper.reactiveweb.domain.Quote;
import org.springframework.data.domain.Pageable;
import org.springframework.data.mongodb.repository.Query;
import org.springframework.data.repository.reactive.ReactiveCrudRepository;
import reactor.core.publisher.Flux;
public interface QuoteMongoReactiveRepository extends ReactiveCrudRepository<Quote, String> {
#Query("{ id: { $exists: true }}")
Flux<Quote> retrieveAllQuotesPaged(final Pageable page);
}
more details , you could check here
I created a service with this method for anyone that may still be looking for a solution:
#Resource
private UserRepository userRepository; //Extends ReactiveSortingRepository<User, String>
public Mono<Page<User>> findAllUsersPaged(Pageable pageable) {
return this.userRepository.count()
.flatMap(userCount -> {
return this.userRepository.findAll(pageable.getSort())
.buffer(pageable.getPageSize(),(pageable.getPageNumber() + 1))
.elementAt(pageable.getPageNumber(), new ArrayList<>())
.map(users -> new PageImpl<User>(users, pageable, userCount));
});
}
I have created another approach using #kn3l solution (without using #Query ):
fun findByIdNotNull(page: Pageable): Flux< Quote>
It creates the same query without using #Query method
public Mono<Page<ChatUser>> findByChannelIdPageable(String channelId, Integer page, Integer size) {
Pageable pageable = PageRequest.of(page, size, Sort.by(Sort.Direction.DESC, "chatChannels.joinedTime"));
Criteria criteria = new Criteria("chatChannels.chatChannelId").is(channelId);
Query query = new Query().with(pageable);
query.addCriteria(criteria);
Flux<ChatUser> chatUserFlux = reactiveMongoTemplate.find(query, ChatUser.class, "chatUser");
Mono<Long> countMono = reactiveMongoTemplate.count(Query.of(query).limit(-1).skip(-1), ChatUser.class);
return Mono.zip(chatUserFlux.collectList(),countMono).map(tuple2 -> {
return PageableExecutionUtils.getPage(
tuple2.getT1(),
pageable,
() -> tuple2.getT2());
});
}
I've faced same issue and end up having similar approach as the above but changed slightly the code as I use Query DSL, following example if someone needed.
#Repository
public interface PersonRepository extends ReactiveMongoRepository<Person, String>, ReactiveQuerydslPredicateExecutor<Person> {
default Flux<Person> applyPagination(Flux<Person> persons, Pageable pageable) {
return persons.buffer(pageable.getPageSize(), (pageable.getPageNumber() + 1))
.elementAt(pageable.getPageNumber(), new ArrayList<>())
.flatMapMany(Flux::fromIterable);
}
}
public Flux<Person> findAll(Pageable pageable, Predicate predicate) {
return personRepository.applyPagination(personRepository.findAll(predicate), pageable);
}
Searching for some idea for reactive pageable repositories I had seen solutions that will result in horrible boiler plate code so I ended up with this (did not tried yet in real life but should work fine, or maybe it can be inspiration for your solution)
So … let's create a brand new toolbox class with such method
public static
<R extends PageableForReactiveMongo<S, K>, S, T, K> Mono<Page<T>>
pageableForReactiveMongo(Pageable pageable,
R repository, Class<T> clazzTo) {
return repository.count()
.flatMap(c ->
repository.findOderByLimitedTo(pageable.getSort(),
pageable.getPageNumber() + 1)
.buffer(pageable.getPageSize(), (pageable.getPageNumber() + 1))
.elementAt(pageable.getPageNumber(), new ArrayList<>())
.map(r -> mapToPage(pageable, c, r, clazzTo))
);
}
and it will need also something like that:
private static <S, T> Page<T> mapToPage(Pageable pageable, Long userCount, Collection<S> collection, Class<T> clazzTo) {
return new PageImpl<>(
collection.stream()
.map(r -> mapper.map(r, clazzTo))
.collect(Collectors.toList())
, pageable, userCount);
}
and then we need also an abstract layer wrapping reactive repositories
public interface PageableForReactiveMongo<D, K> extends ReactiveMongoRepository<D, K> {
Flux<D> findOderByLimitedTo(Sort sort, int i);
}
to let it instantiate by spring
#Repository
interface ControllerRepository extends PageableForReactiveMongo<ControllerDocument, String> {
}
And finally use it many many many times like that
public Mono<Page<Controller>> findAllControllers(Pageable pageable) {
return getFromPageableForReactiveMongo(pageable, controllerRepository, Controller.class);
}
this is how your code can look like :) please tell me if it is fine, or helped out with something
I am using Jersey as the implementation library.
#Path("books")
public class Sample {
#GET
public List<Book> getBooks(#Context UriInfo uriInfo)
{
MultivaluedMap<String,String> params = uriInfo.getQueryParameters();
String pageStart = params.getFirst("p");
String pageSize = params.getFirst("s");
}
}
It works fine with /books but doesn't work for /books?p=1&s=10 (http 404 error)
I don't want to define my path like "books?p={p}&s={s}" since there will be dynamic parameters that cannot be predefined.
question:
Is there any way that i can map /books?p=1&s=10 to the getBooks method??
can check by having you #Path("books") changed to #Path("/books")
Im facing isssue in getting Jersey Generic List in client response. I need to get it as Entity for some reason.
#XmlRootElement(name="list")
#XmlSeeAlso({RESTDomain.class})
public class JAXBContainer<T> {
private List<T> items = new ArrayList<T>();
public JAXBContainer() { }
public JAXBContainer(List<T> items) {
this.items = items;
}
#XmlElementWrapper(name="items")
#XmlAnyElement(lax=true)
public List<T> getItems() {
return items;
}
public void setItems(List<T> items) {
this.items = items;
}
#XmlAttribute
public int getItemsSize() {
return this.items.size();
}
above is my Generic List to the resopnse
#GET
#Produces({MediaType.APPLICATION_XML})
public Response getREST(){
RESTDomain domain = new RESTDomain();
domain.setName("Adams");
domain.setPlace("Zurich");
List<RESTDomain> restDomains = new ArrayList<RESTDomain>();
restDomains.add(domain);
JAXBContainer<RESTDomain> jAXBContainer= new JAXBContainer<RESTDomain>(restDomains);
GenericEntity<JAXBContainer<RESTDomain>> genericEntity = new GenericEntity<JAXBContainer<RESTDomain>>(jAXBContainer){};
return Response.ok(genericEntity).build();
}
Im returning the container with genericEntity. I know with just List inside genericEntity i can get my Entity at my client but the problem is i need to Use my JAXBContainer for some reason.
#Test
public void restGet() throws JAXBException{
ClientConfig cc = new DefaultClientConfig();
client = Client.create(cc);
String baseURI ="http://localhost:3555/SampleREST/rest/sample";
WebResource webResource = client.resource(baseURI);
JAXBContainer<RESTDomain> jAXBContainer= webResource.get(new GenericType<JAXBContainer<RESTDomain>>(){});
System.out.println("response:: "+jAXBContainer.getItemsSize());
}
My problem is im getting the response as JAXBContainer with GenericType as desired but the size of container is 0. What am i missing here? do i have to Use any marshalling and unmarshalling Mechanisms.
But When i request this URI in browser i get the well formed XML, But it fails in client or do we have any other ways to extract entity in client. Thanks in advance
I don't see that you're setting the accept content type anywhere on the client.
Try with: webResource.accept("application/xml")
I'm successfully using Spring.net Rest on WP7 since this issue.
My REST service requires a specific content type. I tried to used another request interceptor but XElementHttpMessageConverter overrides the content type.
public MyClient(string baseAddress)
{
restTemplate = new RestTemplate(baseAddress);
//restTemplate.RequestInterceptors.Add(new NoCacheRequestInterceptor());
restTemplate.MessageConverters.Add(new XElementHttpMessageConverter());
}
public MyObject GetMyObject(int id)
{
XElement element = restTemplate.GetForObject<XElement>("path/{id}", id);
//..
return myObject;
}
// more methods
The best way here to do that is to configure your converter with the "SupportedMediaTypes" property :
public MyClient(string baseAddress)
{
restTemplate = new RestTemplate(baseAddress);
//restTemplate.RequestInterceptors.Add(new NoCacheRequestInterceptor());
XElementHttpMessageConverter linqXmlConverter = new XElementHttpMessageConverter ();
linqXmlConverter.SupportedMediaTypes = new MediaType[] { MediaType.Parse("type/subtype") };
restTemplate.MessageConverters.Add(linqXmlConverter );
}
Btw, you could do that with an interceptor too but not with the "IClientHttpRequestFactoryInterceptor" that intercepts request creation.
You should use instead "IClientHttpRequestBeforeInterceptor" that intercepts request execution.
I'm creating a small REST web service using Netbeans. This is my code:
private UriInfo context;
private String name;
public GenericResource() {
}
#GET
#Produces("text/html")
public String getHtml() {
//TODO return proper representation object
return "Hello "+ name;
}
#PUT
#Consumes("text/html")
public void putHtml(String name) {
this.name = name;
}
I'm calling the get method ok since when I call http://localhost:8080/RestWebApp/resources/greeting I get "Hello null" but I'm trying to pass a parameter using http://localhost:8080/RestWebApp/resources/greeting?name=Krt_Malta but the PUT method is not being called... Is this the correct way to pass a parameter or am I missing something?
I'm a newbie to Rest bdw, so sry if it's a simple question.
Thanks! :)
Krt_Malta
The second URL is a plain GET request. To pass data to a PUT request you have to pass it using a form. The URL is reserved for GET as far as I know.
If you build the HTTP-header yourself, you must use POST instead of GET:
GET /RestWebApp/resources/greeting?name=Krt_Malta HTTP/1.0
versus
POST /RestWebApp/resources/greeting?name=Krt_Malta HTTP/1.0
If you use a HTML-form, you must set the method-attribute to "PUT":
<form action="/RestWebApp/resources/greeting" method="PUT">
For JAX-RS to mactch a method annotated with #PUT, you need to submit a PUT request. Normal browsers don't do this but cURL or a HTTP client library can be used.
To map a query parameter to a method argument, JAX-RS provides the #QueryParam annotation.
public void putWithQueryParam(#QueryParam("name") String name) {
// do something
}
You can set:
#PUT
#path{/putHtm}
#Consumes("text/html")
public void putHtml(String name) {
this.name = name;
}
and if you use something like google`s Volley library you can do.
GsonRequest<String> asdf = new GsonRequest<String>(ConnectionProperties.happyhourURL + "/putHtm", String.class, yourString!!, true,
new Response.Listener<Chain>() {
#Override
public void onResponse(Chain response) {
}
}, new CustomErrorListener(this));
MyApplication.getInstance().addToRequestQueue(asdf);
and GsonRequest will look like:
public GsonRequest(String url, Class<T> _clazz, T object, boolean needLogin, Listener<T> successListener, Response.ErrorListener errorlistener) {
super(Method.PUT, url, errorlistener);
_headers = new HashMap<String, String>();
this._clazz = _clazz;
this.successListener = successListener;
this.needsLogin = needLogin;
_object = object;
setTimeout();
}