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New in Spring 5:Functional Web Framework

Arjen PoutsmaPivotal

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About Arjen

•Twenty years of experience in Enterprise Software Development

• Joined SpringSource in 2005

•Development lead of Spring Web Services, Spring MVC, Spring Scala

•Working on Spring 5

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I do like annotations...

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...but there are downsides

•“Magic”

•No link between data and behavior

• Reflection

• Performance

•Type Erasure

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Design Goals

•Functional Style

•java.util.function

•java.util.stream

•More library; less framework

• Explicit

•Customizable

•No reflection

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Functional Programming(in Java 8)

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Immutability

•No change after construction

• Builders

• Thread-safety

•e.g. String

•toUpperCase()

•StringBuilder

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First-class Functions

•Functions as first-class citizens

• Functions as arguments

• Functions as return value

• Reusability

•e.g. String

•indexOf(char) vs indexOf(Predicate<Char>)

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Pure Functions

•Same result given same arguments

•No Limit side effects

•Application boundaries

• Testability

•Cacheability

• Parallelization

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Demo

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Function<ServerRequest, Mono<? extends ServerResponse>>

HandlerFunction

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ServerRequest

•Similar to RequestEntity

• Immutable

•Headers

• Optional<MediaType> contentType()

• List<String> header(String)

•Body

• Mono<T> bodyToMono(Class<T>)

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ServerResponse

•Similar to ResponseEntity

• Immutable w/ Builder

•Headers

• lastModified(ZonedDateTime)

• header(String, String...)

•Body

• body(Publisher<T>, Class<T>)

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Function<ServerRequest, Mono<HandlerFunction<? extends ServerResponse>>

RouterFunction

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RouterFunctions

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RequestPredicate

Predicate<ServerRequest>

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RequestPredicates

•Common predicates

• path

• headers (Content-Type, Accept)

• Build (compose) your own!

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BiFunction<Request,HandlerFunction<? extends ServerResponse>,

Mono<? extends ServerResponse>>

HandlerFilterFunction

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Running Router Functions

• RouterFunction as @Bean in @EnableWebFlux class

•Convert RouterFunction to HttpHandler

•Reactor Netty

• Tomcat

• Servlet 3.1+

•Undertow

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Demo

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Summary

•Handler functions handle request by returning a response

•Router functions route to handler functions

• Router functions can be filtered by filter functions

• Router functions can be run in a reactive web runtime

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Q & A

Resources

• Sample: https://github.com/poutsma/web-function-sample

• Blog post: https://spring.io/blog/2016/09/22/new-in-spring-5-functional-web-framework

•Kotlin: https://speakerdeck.com/sdeleuze/functional-web-applications-with-spring-and-kotlin

• Reactor: http://projectreactor.io/learn