This tutorial will teach you how to use Keycloak to secure your Spring Boot Application. To find other tutorials, check the Keycloak tutorials page. What is Keycloak? According to Keycloak’s official website, It is an open-source Identity and Access Management solution aimed at modern applications and services. It makes it easy to secure applications and…
Read More A Guide to use Keycloak with Spring BootIn this tutorial, we are going to see how to handle exceptions from a Lambda function in the API Gateway. For Lambda exceptions, we have to map the error status returned by the Lamba functions to the HTTP Status of the methods in API Gateway. If not, the API Gateway returns a 200 OK status…
Read More Handling Exceptions from AWS Lambda written in JAVAThis tutorial is about creating Lambda functions from Spring Cloud Functions. Spring Cloud Functions provide a way to implement the business logic via functions and decouple code development from the runtime target. Hence, the developer can focus solely on the implementation of logic. The developer need not worry about the target endpoint type, connectivity, integration,…
Read More Create AWS Lambda Functions from Spring Cloud Functionsclass ReactiveJavaTutorial { public static void main(String[] args) throws InterruptedException { Flux<String> netFlux = Flux.fromStream(ReactiveJavaTutorial::getVideo) .delayElements(Duration.ofSeconds(2)); // each part will play for 2 seconds // First Subscriber netFlux.subscribe(part -> System.out.println(“Subscriber 1: ” + part)); // wait 5 seconds before next Subscriber joins Thread.sleep(5000); // Seconds Subscriber netFlux.subscribe(part -> System.out.println(“Subscriber 2: ” + part)); Thread.sleep(60000); }…
Read More Hot and Cold Publishers in Project ReactorIn this tutorial, we are going to see how we can use the AWS API Gateway as a trigger to an AWS Lambda function. This tutorial requires you to be familiar with building and deploying Serverless Applications with AWS Lambda. Prerequisite: Build and Deploy a Serverless Spring Boot Web Application with AWS Lambda Firstly, add…
Read More Trigger a Lambda Function Using AWS API GatewayBuild and deploy a Serverless Spring Boot Web Application with AWS Lambda This is a tutorial about creating a basic AWS Lambda function in Java using the Spring framework and requires you to have an active AWS account. If you don’t, go ahead and create one. Lambda is the serverless compute service provided by the…
Read More Build and deploy a Serverless Spring Boot Web Application with AWS Lambdaclass ReactiveJavaTutorial { public static void main(String[] args) { Mono.just(“data1”) .concatWith(Flux.error(new RuntimeException(“Exception occurred.”))) .doOnError(ex -> System.out.println(“LOG: Exception caught: ” + ex)) .retry(3) //retry 3 times in case of an error .log() .subscribe(); } } Output: reactor.Flux.Retry.1 : onSubscribe(FluxRetry.RetrySubscriber) reactor.Flux.Retry.1 : request(unbounded) reactor.Flux.Retry.1 : onNext(data1) LOG: Exception caught: java.lang.RuntimeException: Exception occurred. reactor.Flux.Retry.1 : onNext(data1) LOG: Exception…
Read More RetryFailed Operation in Project Reactorclass ReactiveJavaTutorial { public static void main(String[] args) { Flux.just(2, 7, 10) .concatWith(Flux.error(new RuntimeException(“Exception occurred”))) .concatWith(Mono.just(12)) .log() .subscribe(); } } Output: reactor.Flux.ConcatArray.1 : onSubscribe(FluxConcatArray.ConcatArraySubscriber) reactor.Flux.ConcatArray.1 : request(unbounded) reactor.Flux.ConcatArray.1 : onNext(2) reactor.Flux.ConcatArray.1 : onNext(7) reactor.Flux.ConcatArray.1 : onNext(3) reactor.Flux.ConcatArray.1 : onError(java.lang.RuntimeException: Exception occurred) reactor.Flux.ConcatArray.1 : java.lang.RuntimeException: Exception occurred at com.example.demo.DemoApplication.main(DemoApplication.java:14) ~[classes/:na] You can see that element…
Read More Handling Exceptions in Project Reactorclass ReactiveJavaTutorial { public static void main(String[] args) { Flux.just(“data1”, “data2”, “data3”) .doOnSubscribe(subscription -> System.out.println(“Subscription: ” + subscription)) .subscribe(); } } Output: Subscription: reactor.core.publisher.FluxArray$ArraySubscription@72bca894 doOnNext() method class ReactiveJavaTutorial { public static void main(String[] args) { Flux.just(“data1”, “data2”, “data3”) .doOnNext(data -> System.out.println(“Data: ” + data)) .subscribe(); } } Output: Data: data1 Data: data2 Data: data3 doOnComplete()…
Read More doOn Callbacks in Project Reactorclass ReactiveJavaTutorial { public static void main(String[] args) { Flux<String> firstFlux = Flux.fromArray(new String[]{“a”, “b”, “c”}); Flux<String> secondFlux = Flux.fromArray(new String[]{“d”, “e”, “f”}); // combine two Flux Publishers Flux<String> combinedFlux = Flux.concat(firstFlux, secondFlux); // subscribe and print the elements of a combined Flux combinedFlux.subscribe(element -> System.out.print(element + ” “)); } } Output: a b c…
Read More Combine Flux and Mono Publishersclass ReactiveJavaTutorial { public static void main(String[] args) { Flux.fromArray(new String[]{“Tom”, “Melissa”, “Steve”, “Megan”}) .map(String::toUpperCase) .subscribe(System.out::println); } } Output: TOM MELISSA STEVE MEGAN class ReactiveJavaTutorial { public static void main(String[] args) { Flux.fromArray(new String[]{“Tom”, “Melissa”, “Steven”, “Megan”}) .filter(name -> name.length() > 5) .map(String::toUpperCase) .subscribe(System.out::println); } } Output: MELISSA STEVEN Note: Reactive Streams are immutable.…
Read More Transform Flux and Mono Using OperatorsFlux<String> cities = Flux.fromIterable( new ArrayList<>(Arrays.asList(“New York”, “London”, “Paris”, “Toronto”, “Rome”))); cities.subscribe(); class ReactiveJavaTutorial { public static void main(String[] args) { Flux<String> cities = Flux.fromIterable( new ArrayList<>(Arrays.asList(“New York”, “London”, “Paris”, “Toronto”, “Rome”))); cities.log().subscribe(); } } Output: INFO 6832 — [ main] reactor.Flux.Iterable.1 : | onSubscribe([Synchronous Fuseable] FluxIterable.IterableSubscription) INFO 6832 — [ main] reactor.Flux.Iterable.1 : |…
Read More How Mono and Flux Work Internally?class ReactiveJavaTutorial { public static void main(String[] args) { Mono<String> mono = Mono.just(“data”); Flux<String> fluxFromMono = Flux.from(mono); fluxFromMono.subscribe(System.out::println); } } Output: data class ReactiveJavaTutorial { public static void main(String[] args) { // one value Flux<String> flux1 = Flux.just(“data1”); Mono<String> monoFromFlux1 = flux1.next(); // get data from mono monoFromFlux1.subscribe(data -> System.out.println(“monoFromFlux1 data: ” + data)); //…
Read More Convert Mono to Flux and vice versaclass ReactiveJavaTutorial { public static void main(String[] args) throws InterruptedException { Flux<String> flux = Flux.fromArray(new String[]{“data1”, “data2”, “data3”}); flux.subscribe(System.out::println); } } Output: data1 data2 data3 Another way would be using the Reactive Streams operators like onNext, flatMap, etc. class ReactiveJavaTutorial { public static void main(String[] args) throws InterruptedException { Flux<String> flux = Flux.fromArray(new String[]{“data1”,…
Read More Extract data from Fluxclass ReactiveJavaTutorial { public static void main(String[] args) throws InterruptedException { // Create a Flux Flux<String> flux = Flux.just(“data1”, “data2”, “data3”); // Subscribe to a Flux and print the elements flux.subscribe(System.out::println); } } Output: data1 data2 data3 When we call the subscribe(), we are telling the Publisher to start sending data. class ReactiveJavaTutorial {…
Read More Subscribe to Flux in Java Reactor