The document discusses the development of reactive and non-blocking database connectivity standards. It provides an overview of R2DBC, a standard API for reactive programming with SQL databases on the JVM. Key points include that R2DBC provides an end-to-end non-blocking way to communicate with databases, supports features like transactions and batching, and has driver implementations for several databases. Spring integrates with R2DBC to provide reactive database access in a Spring-friendly way.

1. Full Steam Ahead!
Mark Paluch • Spring Data Project Lead, R2DBC Contributor • @mp911de

2. Reactive Relational Database Connectivity

3. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Mark Paluch
● Spring Data, R2DBC,
Lettuce Redis Driver
● All things non-blocking
● @mp911de (Twitter, GitHub)
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4. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 4
2009
Microsoft to release .NET 4.0
2013
Reactive Manifesto
Initial Akka release
2014
RxJava 1.0
2015
Reactive Streams 1.0
Project Reactor 2.0
2016
RxJava 2.0
Akka Streams 1.0
Ratpack
Spring WebFlux
Micronaut
Today
RSocket
Reactive Mongo
Lettuce
Cassandra
vert.x
Lagom
Apple Servicetalk
Helidon
RxJava 3.0
Project Reactor 3.0

5. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Programming Models Have Changed
● Reactive applications typically stream-processing
● Push-based models
● Notifications, Events
● Is SQL the right choice for reactive applications?
● Depends on the Use-Case
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6. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Reactive Programming
● High-efficiency applications
● Fundamentally non-blocking
● No opinion on async
● Key differentiators: (pull-push) back pressure, flow control
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Persistence
● ✅ Kafka
● ✅ MongoDB
● ✅ Cassandra
● ✅ Couchbase
● ✅ Redis
● ❌ Oracle, DB2, MySQL, MariaDB, Postgres, SQL Server*
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8. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Persistence
● ✅ Kafka
● ✅ MongoDB
● ✅ Cassandra
● ✅ Couchbase
● ✅ Redis
● ❌ Oracle, DB2, MySQL, MariaDB, Postgres, SQL Server*
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9. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Non-blocking SQL Persistence (1/3)
● MySQL: X DevAPI (Document Store API): CompletableFuture
● vert.x Postgres Driver: Callback API
● jasync-sql: CompletableFuture
● Common API 🤕
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Non-blocking SQL Persistence (2/3)
● JDBC on ThreadPool
● RxJava JDBC
● Blocks still threads
● Project Loom: Production readiness unknown
● Requires proper queuing and capacity controls
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11. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Non-blocking SQL Persistence (3/3)
● ADBA (Asynchronous Database API)
● Standard-API
● Based heavily on CompletableFuture
● Discontinued in favor of Project Loom
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Standard API
for reactive programming
with SQL databases
on the JVM

13. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Project of

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Design Principles
● Embrace Reactive Types and Patterns
● Low barrier to entry (depends on Reactive Streams and Java 8 only)
● Non-blocking, all the way to the database
● De-duplicate driver efforts
● Documented specification
● Shrink the driver SPI
● Enable multiple "humane" APIs
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Simple Select
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Publisher<String> values = connectionFactory.create()
.flatMapMany(conn ->
conn.createStatement("SELECT value FROM test")
.execute()
.flatMap(result ->
result.map((row, metadata) -> row.get("value",
String.class))))

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R2DBC 0.8
● Stable release
● End-to-end reactive non-blocking database communication
● Batching
● BLOB/CLOB
● Extensive Type Conversion
● Savepoints
● Transactions
● Leveraging Database-specific features
● ServiceLoader-based Driver discovery
● Connection URLs
● Categorized exceptions (Bad grammar, Data integrity violation, …)
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R2DBC 0.9 / 1.0
● Evolution of the specification
● Extended transaction spec
● Improved In/Out Parameter Bindings
● Investigation on stored procedures
● No real demand so far
● Scheduled for 2021
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R2DBC Ecosystem
● Specification document
● R2DBC SPI
● R2DBC Proxy
● Connection Pooling
● Client Implementations
● Spring
● Querydsl
● R2DBC Migrate
● Kotysa
● Testcontainers
● Driver Community
● Google Cloud Spanner
● H2
● Microsoft SQL Server
● MySQL Driver (r2dbc-mysql,
jasync-sql)
● MariaDB
● PostgreSQL
● SAP Hana
● Oracle (work in progress)
● DB2 (work in progress)
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Community Projects
● Specification document
● R2DBC SPI
● R2DBC Proxy
● Connection Pooling
● Client Implementations
● Spring
● Querydsl
● R2DBC Migrate
● Kotysa
● Testcontainers
● Driver Community
● Google Cloud Spanner
● H2
● Microsoft SQL Server
● MySQL Driver (r2dbc-mysql,
jasync-sql)
● MariaDB
● PostgreSQL
● SAP Hana
● Oracle (work in progress)
● DB2 (work in progress)
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20. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
R2DBC Clients: Work in Progress
● MyBatis (#1444)
● JDBI (#1454)
● jOOQ (#6298)
● Querydsl (#2468)
● Liquibase (CORE-3419)
● Flyway (#2502)
● Exposed (#456)
● Micronaut (#416)
● Go vote for a client you want to see happen.
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21. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
What R2DBC gives you
● Move Thread congestion out of JVM
● Achieve more with less Threads
● Doesn’t change law of physics
● Follow well-known SQL database interaction patterns
● Database laws still apply
● Obey wire protocol rules
● ACID rules
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22. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Spring ❤ R2DBC

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Spring and R2DBC
● 2018/2019
● First steps with Spring Data R2DBC 1.0
● 2020
● Migration of core R2DBC support from Spring Data to Spring
Framework 5.3
● Deprecations in Spring Data R2DBC 1.2
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24. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Spring R2DBC
● Central class: DatabaseClient
● BindMarker SPI
● Reactive Transaction Manager
● Schema initialization support
● ConnectionFactory implementations (e.g.
AbstractRoutingConnectionFactory)
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25. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
DatabaseClient
DatabaseClient client = DatabaseClient.create(connectionFactory);
Flux<Person> people = client
.sql("SELECT firstname, lastname FROM person WHERE age > :age")
.bind("age", 42)
.filter(statement -> statement.fetchSize(20))
.map(row -> new Person(row.get("firstname", String.class),
row.get("lastname", String.class)))
.all();
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26. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
ConnectionFactoryInitializer
@Bean
ConnectionFactoryInitializer initializer(ConnectionFactory connectionFactory) {
ConnectionFactoryInitializer initializer = new ConnectionFactoryInitializer();
initializer.setConnectionFactory(connectionFactory);
initializer.setDatabasePopulator(new ResourceDatabasePopulator(
new ClassPathResource("schema.sql")));
return initializer;
}
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27. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Spring Data R2DBC
● Mapped entity support through R2dbcEntityOperations
● Query and Update objects
● Dialect-awareness
● Repository abstraction
● Sorry, no mapped relations yet
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28. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
R2dbcEntityTemplate
R2dbcEntityTemplate entityTemplate = …;
Flux<Person> people = entityTemplate.select(Person.class)
.from("people")
.matching(query(where("age").greaterThan(42))
.limit(10)
.offset(20)
.sort(by("firstname")))
.all();
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29. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
R2dbcEntityTemplate
R2dbcEntityTemplate entityTemplate = …;
Flux<Person> people = entityTemplate.select(Person.class)
.from("people")
.matching(query(where("age").greaterThan(42))
.limit(10)
.offset(20)
.sort(by("firstname")))
.all();
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query(where("age").greaterThan(42))
.limit(10)
.offset(20)
.sort(by("firstname"))

30. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Repositories
interface PersonRepository extends ReactiveSortingRepository<Person, Integer> {
Flux<Person> findByFirstnameContains(String name);
Flux<Person> findFirst10By();
Flux<Person> findAllByOrderByLastname(Pageable pageable);
@Modifying
@Query("DELETE FROM person WHERE age = :age")
Mono<Void> deleteAllByAge(int age);
@Modifying
@Query("DELETE FROM person")
Mono<Integer> deleteAllAndReturnCount();
}
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31. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Spring Data R2DBC 1.2: New and Noteworthy
● Entity Callbacks
● Before/After Convert, Before/After Save
● Auditing
● SpEL Context Extensions
● Enum value revision
● Repository metrics SPI
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32. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Entity Callbacks
@FunctionalInterface
interface BeforeConvertCallback<T> extends EntityCallback<T> {
Publisher<T> onBeforeConvert(T entity, SqlIdentifier table);
}
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33. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Entity Callback in Action
@Bean
BeforeConvertCallback<Person> autogeneratedId(DatabaseClient client) {
return (entity, table) -> {
if (entity.getId() == null) {
return client.sql("SELECT nextval('person_seq')")
.map(row -> row.get(0, Integer.class))
.first()
.map(entity::withId);
}
return Mono.just(entity);
};
}
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34. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Outlook: Spring Data R2DBC 2.0
● Closer alignment of Spring Data JDBC and Spring Data R2DBC
● Evolution of Spring Data Relational
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35. Thank you.
r2dbc.io
@mp911de

36. Unless otherwise indicated, these slides are © 2013-2020 vmware and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/
Resources
● Website
https://r2dbc.io
● Twitter
@r2dbc
● GitHub
https://github.com/r2dbc
● Mailing List
https://groups.google.com/forum/
#!forum/r2dbc
● Monthly Call
1st Friday of Month
0630 PT/0930 ET/1530 CET
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