DATACOUCH-295 - Add documentation for reactive support

Original pull request: #145.

src/main/asciidoc/reactiverepository.adoc

@@ -0,0 +1,118 @@
+[[couchbase.reactiverepository]]
+= Reactive Couchbase repository
+
+[[couchbase.reactiverepository.intro]]
+== Introduction
+
+This chapter describes the reactive repository support for couchbase. This builds on the core repository support explained in <<couchbase.repository>>.
+So make sure you’ve got a sound understanding of the basic concepts explained there.
+
+[[couchbase.reactiverepository.libraries]]
+== Reactive Composition Libraries
+
+Couchbase Java SDK 2.x has taken a reactive programming approach since its inception using an early reactive extension to JVM, https://github.com/ReactiveX/RxJava/tree/1.x/[RxJava1].
+It provides RxJava1 observable sequence API to compose asynchronous database operations.
+
+Reactive Couchbase repositories provide project Reactor wrapper types and can be used by simply extending from one of the library-specific repository interfaces:
+
+* ReactiveCrudRepository
+
+* ReactiveSortingRepository
+
+Spring-data-couchbase converts RxJava 1 observables to reactor types by using reactive-streams adapters from https://github.com/ReactiveX/[RxJavaReactiveStreams]
+for convenience since these conversions can easily clutter application code. This transformation happens on same thread. It also provides direct access to RxJava1 observable
+sequence API from SDK through RxJavaCouchbaseOperations methods.
+
+[[couchbase.reactiverepository.usage]]
+== Usage
+To access domain entities stored in a Couchbase bucket you can leverage our sophisticated repository support that eases implementing those quite significantly.
+To do so, simply create an interface for your repository:
+
+.Sample Person entity
+====
+[source,java]
+----
+public class Person {
+
+  @Id
+  private String id;
+  private String firstname;
+  private String lastname;
+  private Address address;
+
+  // … getters and setters omitted
+}
+----
+====
+
+We have a quite simple domain object here.
+
+.Basic repository interface to persist Person entities
+====
+[source]
+----
+public interface ReactivePersonRepository extends ReactiveSortingRepository<Person, Long> {
+
+  Flux<Person> findByFirstname(String firstname);
+
+  Flux<Person> findByFirstname(Publisher<String> firstname);
+
+  Flux<Person> findByFirstnameOrderByLastname(String firstname, Pageable pageable);
+
+  Mono<Person> findByFirstnameAndLastname(String firstname, String lastname);
+}
+----
+====
+
+For JavaConfig use the `@EnableReactiveCouchbaseRepositories` annotation. The annotation carries the very same attributes like the namespace element. If no base package is configured the infrastructure will scan the package of the annotated configuration class.
+
+.JavaConfig for repositories
+====
+[source,java]
+----
+@Configuration
+@EnableReactiveCouchbaseRepositories
+class ApplicationConfig extends AbstractReactiveCouchbaseConfiguration {
+
+  @Override
+  protected List<String> getBootstrapHosts() {
+    return Collections.singletonList("127.0.0.1");
+  }
+
+  @Override
+  protected String getBucketName() {
+  		return "default";
+  }
+
+  @Override
+  protected String getBucketPassword() {
+ 	return "";
+ }
+}
+----
+====
+
+As our domain repository extends `ReactiveSortingRepository` it provides you with CRUD operations as well as methods for sorted access to the entities. Working with the repository instance is just a matter of dependency injecting it into a client.
+
+.Sorted access to Person entities
+====
+[source,java]
+----
+public class PersonRepositoryTests {
+
+    @Autowired
+    ReactivePersonRepository repository;
+
+    @Test
+    public void sortsElementsCorrectly() {
+      Flux<Person> persons = repository.findAll(Sort.by(new Order(ASC, "lastname")));
+      assertNotNull(perons);
+    }
+}
+----
+====
+
+[[couchbase.reactiverepository.querying]]
+== Repositories and Querying
+
+Spring Data's Reactive Couchbase comes with full querying support already provided by the blocking <<couchbase.repository.querying>>