#215 - Add reactive examples for MongoDB, Apache Cassandra and Redis.

cassandra/reactive/README.md

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+# Spring Data Cassandra 2.0 - Reactive examples
+
+This project contains samples of reactive data access features with Spring Data (Cassandra).
+
+## Reactive Template API usage with `ReactiveCassandraTemplate` 
+
+The main reactive Template API class is `ReactiveCassandraTemplate`, ideally used through its interface `ReactiveCassandraOperations`. It defines a basic set of reactive data access operations using [Project Reactor](http://projectreactor.io) `Mono` and `Flux` reactive types.
+
+```java
+template.insert(Flux.just(new Person("Walter", "White", 50),
+				new Person("Skyler", "White", 45),
+				new Person("Saul", "Goodman", 42),
+				new Person("Jesse", "Pinkman", 27)));
+				
+Flux<Person> flux = template.select(select()
+                                         .from("person")
+                                         .where(eq("lastname", "White")), Person.class);
+```
+
+The test cases in `ReactiveCassandraTemplateIntegrationTest` show basic Template API usage. 
+Reactive data access reads and converts individual elements while processing the stream.
+
+
+## Reactive Repository support
+ 
+Spring Data Cassandra provides reactive repository support with Project Reactor and RxJava 1 reactive types. The reactive API supports reactive type conversion between reactive types.
+
+```java
+public interface ReactivePersonRepository extends ReactiveCrudRepository<Person, String> {
+
+	Flux<Person> findByLastname(String lastname);
+
+	@Query("SELECT * FROM person WHERE firstname = ?0 and lastname  = ?1")
+	Mono<Person> findByFirstnameAndLastname(String firstname, String lastname);
+
+	// Accept parameter inside a reactive type for deferred execution
+	Flux<Person> findByLastname(Mono<String> lastname);
+	
+	Mono<Person> findByFirstnameAndLastname(Mono<String> firstname, String lastname);
+	
+	@InfiniteStream // Use a tailable cursor
+	Flux<Person> findWithTailableCursorBy();
+}
+```
+
+```java
+public interface RxJava1PersonRepository extends RxJava1CrudRepository<Person, String> {
+
+	Observable<Person> findByLastname(String lastname);
+
+	@Query("SELECT * FROM person WHERE firstname = ?0 and lastname  = ?1")
+	Single<Person> findByFirstnameAndLastname(String firstname, String lastname);
+	
+	// Accept parameter inside a reactive type for deferred execution
+	Observable<Person> findByLastname(Single<String> lastname);
+	
+	Single<Person> findByFirstnameAndLastname(Single<String> firstname, String lastname);
+
+	@InfiniteStream // Use a tailable cursor
+	Observable<Person> findWithTailableCursorBy();
+}
+```
+
+## Preparation
+
+### Install Cassandra
+
+Before we can start we have to install Cassandra, e.g. via brew on Max OS.
+
+More details can be found here: https://wiki.apache.org/cassandra/GettingStarted
+
+### Start Cassandra
+
+```
+/usr/local/bin/cassandra -f 
+```
+
+That should be enough to get you started.
+Now you can simply type ```mvn clean install``` to run the example.