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Spring Webflux tutorial: how to build reactive web applications
2021-08-25 15:04:30 【Old K's Java blog】
Reactive systems allow the unparalleled responsiveness and scalability we need in a high data flow world . However , Reactive systems require specially trained tools and developers to implement these unique program architectures .Spring WebFlux with Project Reactor It is a framework specially built to meet the reactivity needs of modern companies .
today , We're going to explain it WebFlux How to match with other reactive stack tools 、 How different and how to make the first application to help you get started WebFlux.
What is a reactive system ?
Reactive system is a system designed with reactive architecture pattern , This pattern takes precedence over loose coupling 、 Flexible and scalable components . They also designed fault solutions , To ensure that even if one system fails , Most systems still work .
Reactive systems focus on :
- Reactivity : most important of all , Reactive systems should respond quickly to any user input . Proponents of reactive systems believe that , Reactivity helps optimize all other parts of the system , From data collection to user experience .
- elastic : The reactive system shall be designed to predict system failure . Reactive systems expect components to eventually fail , And design loosely coupled systems , Even if several individual parts stop working , Can also remain active .
- elastic : Reactive systems should be scaled up or down to meet requirements to adapt to the size of the workload . Many reactive systems will also use predictive scaling to predict and prepare for sudden changes . The key to achieving resilience is to eliminate any bottlenecks , Build systems that can split or copy components as needed .
- Message driven communication : All the components of a reactive system are loosely coupled , There are hard boundaries between each component . Your system should communicate across these boundaries through explicit messaging . These messages make different components aware of the fault , And help them delegate the workflow to components that can handle it .
Reactions and other web The most significant difference between patterns is , Reactive systems can execute multiple unblocked calls at once , Instead of having some calls wait for others . therefore , Reactive systems can speed up performance and response , because web Each part of the application can complete its own part faster than waiting for another part .
In short , Reactive systems use loose coupling 、 Non blocking components to improve performance 、 User experience and error handling .
What is? Project Reactor?
Project Reactor By Pivotal Framework built , from Spring powered . It realizes the reaction API Pattern , The most significant is the reactive flow specification .
If you are familiar with Java8 flow , You'll soon find streams and traffic ( Or its single element version Mono) There are many similarities between . The main difference between them is Flux and Monos Follow the publisher - Subscriber mode and implement back pressure , and StreamAPI There is no .
Back pressure is a signal from the data endpoint to the data producer , A way of indicating that it receives too much data . This allows better flow management and distribution , Because it prevents individual components from overworking .
Use Reactor The main advantage of is that you have complete control over the data flow . You can rely on the ability of subscribers to request more information when they are ready to process information , Or buffer some results on the publisher side , Even use the complete push method without back pressure .
In our reactive stack , It is located in Spring Boot 2.0 Lower and WebFlux above :
What is? Spring WebFlux?
Spring WebFlux Is a completely non blocking 、 Annotation based web frame , It is built on ProjectReactor On , Make in HTTP It is possible to build reactive applications on the layer .WebFlux Apply functional programming to... Using a new router functional feature web layer , And bypass declarative controllers and request mappings .WebFlux You are required to Reactor Import... As a core dependency .
WebFlux Is in Spring 5 Added in , As Spring MVC A passive alternative to , And added support for the following aspects :
- Nonblocking thread : A concurrent thread that completes its specified task without waiting for the previous task to complete .
- Reactive Stream API: A standardized tool , Includes asynchronous flow processing options and non blocking back pressure .
- Asynchronous data processing : When data is processed in the background , Users can continue to use normal application functions without interruption .
Final ,WebFlux To cancel the SpringMVCs Per request thread model , But use multi-EventLoop Non blocking model to support reactive 、 Scalable applications . Because of the support Netty、Undertow and Servlet3.1+ Containers and other popular servers ,WebFlux Has become a key part of the reactive stack .
Spring WebFlux Significant characteristics of
Router function
RouterFunction It's a standard. SpringMVC Used in @RequestMapping
and @Controller
Functional alternatives to annotation styles .
We can use it to route requests to handler functions :
@RestControllerpublic class ProductController { @RequestMapping("/product") public List<Product> productListing() { return ps.findAll(); }}
You can use RouterFunctions.route()
Create route , Instead of writing complete router functions . Route is registered as Springbean
, So you can create... In any configuration class .
The router function avoids the potential side effects caused by the multi-step process of request mapping , Instead, it's reduced to a direct router / Handler chain . This allows the functional programming implementation of reactive programming .
RequestMapping
and Controller
The annotation style is in WebFlux It still works , If you are more familiar with the old style ,RouterFunction
It's just a new option for the solution .
WebClient
WebClient yes WebFlux The reaction of web client , By the famous RestTemplate structure . It's an interface , Express web The main entry point of the request , And supports synchronous and asynchronous operations .WebClient It is mainly used for reactive back-end to back-end communication .
You can use the Maven Import standards WebFlux Dependencies to build and create WebClient example :
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-webflux</artifactId></dependency>
WebClient client = WebClient.create();
Reactive Steam API
Reactive Steam API Is a collection of imported functions , Allow more intelligent streaming data streams . It has built-in support for back pressure and asynchronous processing , Ensure that applications make the most efficient use of computer and component resources .
Reaction flow API There are four main interfaces in :
1. Publisher: Send events to link subscribers according to their needs . Act as the central link point where subscribers can monitor events .
2. Subscriber: Receive and process events from the publisher . Multiple subscribers can link to a single publisher , And respond differently to the same event . Subscribers can be set to respond :
onNext
, When it receives the next event .onSubscribe
, When adding a new subscriberonError
, When another subscriber has an erroronComplete
, When another subscriber completes its task
3. Subscription: Define the relationship between the selected publisher and subscriber . Each subscriber can only link to one publisher .
4. Processor: Represents the processing phase of the subscriber
Servers
WebFlux stay Tomcat、Jetty、Servlet3.1+ Containers and Netty and Undertow Such as the Servlet Supported on runtime .Netty Most commonly used in asynchronous and non blocking designs , therefore WebFlux It will be used by default . Only need to Maven or Gradle Build software and make simple changes , You can easily switch between these Server Options .
This makes WebFlux It is highly versatile in terms of available technologies , And allows you to easily implement it in your existing infrastructure .
Concurrency model
WebFlux Non blocking is considered in the construction of , So we use the same as SpringMVC Different concurrent programming models .
SpringMVC Suppose the thread will be blocked , And use a large thread pool to keep moving during blocking instances . This larger thread pool makes MVC More resource intensive , Because the computer hardware must keep more threads running at the same time .
WebFlux Used a small thread pool , Because it assumes that you never need to work to avoid blocking . These threads are called event loop worker threads , It is fixed in quantity , Loop speed in incoming requests is faster than MVC Fast thread . It means WebFlux Computer resources can be used more effectively , Because the active thread is always working .
Spring WebFlux Security
WebFlux Use Spring Security Implement authentication and authorization protocols .Spring Security Use WebFilter Check the request against the list of authenticated users , It can also be set to automatically reject requests that meet conditions such as source or request type .
@EnableWebFluxSecuritypublic class HelloWebFluxSecurityConfig { @Bean public MapReactiveUserDetailsService userDetailsService() { UserDetails user = User.withDefaultPasswordEncoder() .username("user") .password("user") .roles("USER") .build(); return new MapReactiveUserDetailsService(user); }}
This is the smallest implementation that sets all settings to the default . ad locum , We can see that the user has a user name 、 One password and one or more role tags , Allow them a certain degree of access .
Start using SpringWebFlux
Now? , Let's experience WebFlux. First , We need to build a project . We will use SpringInitializer Generate a file with SpringReactiveWeb
Dependent Maven structure .
This will generate a file like pom.xml
<?xml version="1.0" encoding="UTF-8"?><project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.4.2</version> <relativePath/> <!-- lookup parent from repository --> </parent> <groupId>com.example</groupId> <artifactId>reactive-rest-service</artifactId> <version>0.0.1-SNAPSHOT</version> <name>reactive-rest-service</name> <description>Demo project for Spring Boot</description> <properties> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-webflux</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>io.projectreactor</groupId> <artifactId>reactor-test</artifactId> <scope>test</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build></project>
Now you have everything you need to continue ! From here, we will add some components to make Hello World Applications . We will only add a router and a handler , This is the basis for creating WebFlux Minimum requirements for applications .
Router
First , We will create a sample router , stay URL Show text last time http://localhost:8080/example
. This defines how the user requests the data we will define in the handler .
@Configurationpublic class ExampleRouter { @Bean public RouterFunction<ServerResponse> routeExample (ExampleHandler exampleHandler) { return RouterFunctions .route(RequestPredicates.GET("/example").and(RequestPredicates.accept(MediaType.TEXT_PLAIN)), exampleHandler::hello); }}
Handler
Now? , We will add a handler , Used to listen for requests / Any user of the sample route . Once the router recognizes that the requested path matches , It sends the user to the handler . Our handler receives the message and takes the user to the page with our greeting .
@Componentpublic class ExampleHandler { public Mono<ServerResponse> hello(ServerRequest request) { return ServerResponse.ok().contentType(MediaType.TEXT_PLAIN) .body(BodyInserters.fromObject("Hello, Spring WebFlux Example!")); }}
Running the application
Now? , We will implement Maven command spring boot:run
To run the application . You can now access http://localhost:8080/example
Find... In the browser :
Hello, Spring WebFlux Example!
Original address :https://www.educative.io/blog/spring-webflux-tutorial
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author[Old K's Java blog],Please bring the original link to reprint, thank you.
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