15.SpringBoot學習(十五)——Spring Boot WebFlux路由

1.簡介

1.1 概述

In WebFlux.fn, an HTTP request is handled with a HandlerFunction: a function that takes ServerRequest and returns a delayed ServerResponse (i.e. Mono<ServerResponse>). Both the request and the response object have immutable contracts that offer JDK 8-friendly access to the HTTP request and response. HandlerFunction is the equivalent of the body of a @RequestMapping method in the annotation-based programming model.

Incoming requests are routed to a handler function with a RouterFunction: a function that takes ServerRequest and returns a delayed HandlerFunction (i.e. Mono<HandlerFunction>). When the router function matches, a handler function is returned; otherwise an empty Mono. RouterFunction is the equivalent of a @RequestMapping annotation, but with the major difference that router functions provide not just data, but also behavior.

RouterFunctions.route() provides a router builder that facilitates the creation of routers, as the following example shows:

在WebFlux.fn中，HTTP請求由HandlerFunction處理：該函數接受ServerRequest並返回延遲的ServerResponse（即Mono ）。請求和響應對象都具有不可變的協定，這些協定為JDK 8提供了對HTTP請求和響應的友好訪問。 HandlerFunction等效於基於注釋的編程模型中@RequestMapping方法的主體。傳入的請求被路由到帶有RouterFunction的處理程序函數：該函數接受ServerRequest並返回延遲的HandlerFunction（即Mono ）。當路由器功能匹配時，返回處理程序功能。否則為空Mono。 RouterFunction等效於@RequestMapping批注，但主要區別在於路由器功能不僅提供數據，而且還提供行為。 RouterFunctions.route() 提供了一個路由器構建器，可簡化路由器的創建過程。

1.2 特點

Router functions are used to route the requests to the corresponding HandlerFunction. Typically, you do not write router functions yourself, but rather use a method on the RouterFunctions utility class to create one. RouterFunctions.route() (no parameters) provides you with a fluent builder for creating a router function, whereas RouterFunctions.route(RequestPredicate, HandlerFunction) offers a direct way to create a router.

Generally, it is recommended to use the route() builder, as it provides convenient short-cuts for typical mapping scenarios without requiring hard-to-discover static imports. For instance, the router function builder offers the method GET(String, HandlerFunction) to create a mapping for GET requests; and POST(String, HandlerFunction) for POSTs.

Besides HTTP method-based mapping, the route builder offers a way to introduce additional predicates when mapping to requests. For each HTTP method there is an overloaded variant that takes a RequestPredicate as a parameter, though which additional constraints can be expressed.

路由器功能用於將請求路由到相應的HandlerFunction。通常，您不是自己編寫路由器功能，而是使用RouterFunctions實用程序類上的方法創建一個。 RouterFunctions.route()(無參數)為您提供了一個流暢的生成器來創建路由器功能，而RouterFunctions.route(RequestPredicate，HandlerFunction)提供了直接創建路由器的方法。通常，建議使用route()構建器，因為它為典型的映射方案提供了便捷的捷徑，而無需發現靜態導入。例如，路由器功能構建器提供了GET(String，HandlerFunction)方法來為GET請求創建映射。和POST(String，HandlerFunction)進行POST。除了基於HTTP方法的映射外，路由構建器還提供了一種在映射到請求時引入其他謂詞的方法。對於每個HTTP方法，都有一個以RequestPredicate作為參數的重載變體，盡管可以表達其他約束。

2.演示環境

1. JDK 1.8.0_201
2. Spring Boot 2.2.0.RELEASE
3. 構建工具（apache maven 3.6.3）
4. 開發工具（IntelliJ IDEA ）

3.演示代碼

3.1 代碼說明

使用 RouterFunction 的方式使用 webflux

3.2 代碼結構

3.3 maven 依賴

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-webflux</artifactId>
    </dependency>
</dependencies>

3.4 配置文件

無配置

3.5 java代碼

UserModel.java

public class UserModel {

    private Long id;
    private String name;
    private Integer age;
    private String birthday;
    private String address;
    private String phone;

    public UserModel() {}

    public UserModel(Long id, String name, Integer age, String birthday, String address, String phone) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.birthday = birthday;
        this.address = address;
        this.phone = phone;
    }
	
    // get&set&toString
}

UserRepository.java

@Repository
public class UserRepository {

    // 預置兩條數據，所以起始值從2開始
    private static final AtomicLong ID_GENERATOR = new AtomicLong(2);

    // 模擬數據庫操作
    private static final Map<Long, UserModel> USER_MAP = new HashMap<>();

    @PostConstruct
    public void init() {
        UserModel user1 = new UserModel(1L, "zhangsan", 20, "2000-01-02", "beijing", "13666666666");
        UserModel user2 = new UserModel(2L, "lisi", 30, "1990-03-23", "shanghai", "13888888888");
        USER_MAP.put(user1.getId(), user1);
        USER_MAP.put(user2.getId(), user2);
    }

    public List<UserModel> findAll() {
        return new ArrayList<>(USER_MAP.values());
    }

    public UserModel findById(Long id) {
        return USER_MAP.get(id);
    }

    public UserModel add(UserModel userModel) {
        long id = ID_GENERATOR.incrementAndGet();
        userModel.setId(id);
        USER_MAP.put(id, userModel);
        return userModel;
    }

    public UserModel update(UserModel userModel) {
        USER_MAP.put(userModel.getId(), userModel);
        return USER_MAP.get(userModel.getId());
    }

    public UserModel deleteById(Long id) {
        UserModel userModel = USER_MAP.get(id);
        USER_MAP.remove(id);
        return userModel;
    }
}

UserHandler.java

@Component
public class UserHandler {

    @Autowired
    private UserRepository userRepository;

    public Mono<ServerResponse> list(ServerRequest request) {
        // ServerResponse.ok().body(Flux.fromIterable(userRepository.findAll()), UserModel.class);
        return ServerResponse.ok().body(Flux.fromStream(userRepository.findAll().stream()), UserModel.class);
    }

    public Mono<ServerResponse> findById(ServerRequest request) {
        return Mono.justOrEmpty(userRepository.findById(Long.valueOf(request.pathVariable("id"))))
            .flatMap(user -> ServerResponse.ok().body(Mono.just(user), UserModel.class))
            .switchIfEmpty(ServerResponse.notFound().build()); // 輸出 404 Not Found
    }

    public Mono<ServerResponse> add(ServerRequest request) {
        return ServerResponse.ok().body(
            request.bodyToMono(UserModel.class).flatMap(userModel -> Mono.just(userRepository.add(userModel))),
            UserModel.class);
    }

    public Mono<ServerResponse> update(ServerRequest request) {
        /*request.bodyToMono(UserModel.class)
            .flatMap(user -> Mono.justOrEmpty(userRepository.findById(user.getId()))
                .then(ServerResponse.ok().body(Mono.just(userRepository.update(user)), UserModel.class))
                // .switchIfEmpty(Mono.error(new NotFoundException(String.valueOf(user.getId())))))
                .switchIfEmpty(ServerResponse.notFound().build()));*/

        return request.bodyToMono(UserModel.class)
            .flatMap(body -> Mono.justOrEmpty(userRepository.findById(body.getId())).flatMap(foundUser -> {
                foundUser.setAge(body.getAge());
                foundUser.setName(body.getName());
                foundUser.setBirthday(body.getBirthday());
                foundUser.setAddress(body.getAddress());
                foundUser.setPhone(body.getPhone());
                return Mono.just(foundUser);
            }).flatMap(u -> ServerResponse.ok().body(fromObject(u))).switchIfEmpty(ServerResponse.notFound().build()));
    }

    public Mono<ServerResponse> deleteById(ServerRequest request) {
        Long id = Long.valueOf(request.pathVariable("id"));
        return Mono.justOrEmpty(userRepository.findById(id))
            .switchIfEmpty(Mono.error(new RuntimeException(id + "not found!"))) // 控制台異常：RuntimeException: 30
            .then(ServerResponse.ok().body(Mono.justOrEmpty(userRepository.deleteById(id)), UserModel.class));
    }

    public Mono<ServerResponse> deleteId(ServerRequest request) {
        Long id = Long.valueOf(request.pathVariable("id"));
        return Mono.justOrEmpty(userRepository.findById(id))
            .flatMap(user -> ServerResponse.ok().body(Mono.just(userRepository.deleteById(id)), UserModel.class))
            .switchIfEmpty(ServerResponse.notFound().build());
    }
}

UserRouter.java

import static org.springframework.web.reactive.function.server.RequestPredicates.DELETE;
import static org.springframework.web.reactive.function.server.RequestPredicates.GET;
import static org.springframework.web.reactive.function.server.RequestPredicates.POST;
import static org.springframework.web.reactive.function.server.RequestPredicates.PUT;
import static org.springframework.web.reactive.function.server.RequestPredicates.accept;
import static org.springframework.web.reactive.function.server.RequestPredicates.contentType;
import static org.springframework.web.reactive.function.server.RouterFunctions.route;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.MediaType;
import org.springframework.web.reactive.function.server.RouterFunction;
import org.springframework.web.reactive.function.server.ServerResponse;

@Configuration
public class UserRouter {

    @Autowired
    private UserHandler userHandler;

    @Bean
    public RouterFunction<ServerResponse> routerFunction() {
        return route(GET("/user/list").and(accept(MediaType.APPLICATION_JSON)), userHandler::list)
            .andRoute(GET("/user/find/{id}").and(accept(MediaType.APPLICATION_JSON)), userHandler::findById)
            .andRoute(POST("/user/add").and(contentType(MediaType.APPLICATION_JSON)), userHandler::add)
            .andRoute(PUT("/user/update").and(contentType(MediaType.APPLICATION_JSON)), userHandler::update)
            .andRoute(DELETE("/user/delete/{id}"), userHandler::deleteId);
    }
}

3.6 git 地址

spring-boot/spring-boot-07-webflux/spring-boot-webflux-router

4.效果展示

啟動 SpringBootWebfluxRouterApplication.main 方法，在 spring-boot-webflux-router.http 訪問下列地址，觀察輸出信息是否符合預期。

查詢用戶列表

### GET /user/list
GET http://localhost:8080/user/list
Accept: application/json

根據id查詢用戶

### GET /user/find/{id}
GET http://localhost:8080/user/find/1
Accept: application/json

新增用戶

### POST /user/add
POST http://localhost:8080/user/add
Accept: application/json
Content-Type: application/json

{
  "name": "wangwu",
  "age": 25,
  "birthday": "1995-06-23",
  "address": "guangzhou",
  "phone": "13777777777"
}

更新用戶（成功）

### PUT /user/update success
PUT http://localhost:8080/user/update
Accept: application/json
Content-Type: application/json

{
  "id": 2,
  "name": "lisi2",
  "age": 32,
  "birthday": "1988-03-23",
  "address": "shanghai2",
  "phone": "13888888882"
}

更新用戶（失敗）

### PUT /user/update fail  // 404 Not Found (id)
PUT http://localhost:8080/user/update
Accept: application/json
Content-Type: application/json

{
  "id": 222,
  "name": "lisi2",
  "age": 32,
  "birthday": "1988-03-23",
  "address": "shanghai2",
  "phone": "13888888882"
}

刪除用戶

### DELETE /user/delete/{id}
DELETE http://localhost:8080/user/delete/3
Accept: application/json

5.源碼分析

5.1 Webflux Server 如何啟動？

使用 webflux 時，默認的 applicationContext 為 AnnotationConfigReactiveWebServerApplicationContext

protected ConfigurableApplicationContext createApplicationContext() {
    Class<?> contextClass = this.applicationContextClass;
    if (contextClass == null) {
        try {
            switch (this.webApplicationType) {
                case SERVLET:
                    contextClass = Class.forName(DEFAULT_SERVLET_WEB_CONTEXT_CLASS);
                    break;
                case REACTIVE:
                    contextClass = Class.forName(DEFAULT_REACTIVE_WEB_CONTEXT_CLASS);
                    break;
                default:
                    contextClass = Class.forName(DEFAULT_CONTEXT_CLASS);
            }
        }
        catch (ClassNotFoundException ex) {
            throw new IllegalStateException(
                "Unable create a default ApplicationContext, please specify an ApplicationContextClass", ex);
        }
    }
    return (ConfigurableApplicationContext) BeanUtils.instantiateClass(contextClass);
}

所以在 AnnotationConfigReactiveWebServerApplicationContext 中進行初始化和啟動

5.2 Webflux 默認 Server 為何是 Netty？

先看下 spring-boot-starter-webflux 的依賴結構

在 spring-boot-autoconfigure/spring.factories 中有一個自動裝配的類 ReactiveWebServerFactoryAutoConfiguration

它的內容如下

@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(ReactiveHttpInputMessage.class)
@ConditionalOnWebApplication(type = ConditionalOnWebApplication.Type.REACTIVE)
@EnableConfigurationProperties(ServerProperties.class)
@Import({ ReactiveWebServerFactoryAutoConfiguration.BeanPostProcessorsRegistrar.class,
         ReactiveWebServerFactoryConfiguration.EmbeddedTomcat.class,
         ReactiveWebServerFactoryConfiguration.EmbeddedJetty.class,
         ReactiveWebServerFactoryConfiguration.EmbeddedUndertow.class,
         ReactiveWebServerFactoryConfiguration.EmbeddedNetty.class })
public class ReactiveWebServerFactoryAutoConfiguration {

    @Bean
    public ReactiveWebServerFactoryCustomizer reactiveWebServerFactoryCustomizer(ServerProperties serverProperties) {
        return new ReactiveWebServerFactoryCustomizer(serverProperties);
    }

    @Bean
    @ConditionalOnClass(name = "org.apache.catalina.startup.Tomcat")
    public TomcatReactiveWebServerFactoryCustomizer tomcatReactiveWebServerFactoryCustomizer(
        ServerProperties serverProperties) {
        return new TomcatReactiveWebServerFactoryCustomizer(serverProperties);
    }

    @Bean
    @ConditionalOnMissingBean
    @ConditionalOnProperty(value = "server.forward-headers-strategy", havingValue = "framework")
    public ForwardedHeaderTransformer forwardedHeaderTransformer() {
        return new ForwardedHeaderTransformer();
    }

    /**
    * Registers a {@link WebServerFactoryCustomizerBeanPostProcessor}. Registered via
    * {@link ImportBeanDefinitionRegistrar} for early registration.
    */
    public static class BeanPostProcessorsRegistrar implements ImportBeanDefinitionRegistrar, BeanFactoryAware {

        private ConfigurableListableBeanFactory beanFactory;

        @Override
        public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
            if (beanFactory instanceof ConfigurableListableBeanFactory) {
                this.beanFactory = (ConfigurableListableBeanFactory) beanFactory;
            }
        }

        @Override
        public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
            if (this.beanFactory == null) {
                return;
            }
            registerSyntheticBeanIfMissing(registry, "webServerFactoryCustomizerBeanPostProcessor",
                                           WebServerFactoryCustomizerBeanPostProcessor.class);
        }

        private void registerSyntheticBeanIfMissing(BeanDefinitionRegistry registry, String name, Class<?> beanClass) {
            if (ObjectUtils.isEmpty(this.beanFactory.getBeanNamesForType(beanClass, true, false))) {
                RootBeanDefinition beanDefinition = new RootBeanDefinition(beanClass);
                beanDefinition.setSynthetic(true);
                registry.registerBeanDefinition(name, beanDefinition);
            }
        }
    }
}

它里面通過 @Import 分別引入了 EmbeddedTomcat、EmbeddedJetty、EmbeddedUndertow、EmbeddedNetty，它們都是 ReactiveWebServerFactoryConfiguration 的內部類

abstract class ReactiveWebServerFactoryConfiguration {

    @Configuration(proxyBeanMethods = false)
    @ConditionalOnMissingBean(ReactiveWebServerFactory.class)
    @ConditionalOnClass({ HttpServer.class })
    static class EmbeddedNetty {

        @Bean
        @ConditionalOnMissingBean
        ReactorResourceFactory reactorServerResourceFactory() {
            return new ReactorResourceFactory();
        }

        @Bean
        NettyReactiveWebServerFactory nettyReactiveWebServerFactory(ReactorResourceFactory resourceFactory,
                                                                    ObjectProvider<NettyRouteProvider> routes, ObjectProvider<NettyServerCustomizer> serverCustomizers) {
            NettyReactiveWebServerFactory serverFactory = new NettyReactiveWebServerFactory();
            serverFactory.setResourceFactory(resourceFactory);
            routes.orderedStream().forEach(serverFactory::addRouteProviders);
            serverFactory.getServerCustomizers().addAll(serverCustomizers.orderedStream().collect(Collectors.toList()));
            return serverFactory;
        }

    }

    @Configuration(proxyBeanMethods = false)
    @ConditionalOnMissingBean(ReactiveWebServerFactory.class)
    @ConditionalOnClass({ org.apache.catalina.startup.Tomcat.class })
    static class EmbeddedTomcat {

        @Bean
        TomcatReactiveWebServerFactory tomcatReactiveWebServerFactory(
            ObjectProvider<TomcatConnectorCustomizer> connectorCustomizers,
            ObjectProvider<TomcatContextCustomizer> contextCustomizers,
            ObjectProvider<TomcatProtocolHandlerCustomizer<?>> protocolHandlerCustomizers) {
            TomcatReactiveWebServerFactory factory = new TomcatReactiveWebServerFactory();
            factory.getTomcatConnectorCustomizers()
                .addAll(connectorCustomizers.orderedStream().collect(Collectors.toList()));
            factory.getTomcatContextCustomizers()
                .addAll(contextCustomizers.orderedStream().collect(Collectors.toList()));
            factory.getTomcatProtocolHandlerCustomizers()
                .addAll(protocolHandlerCustomizers.orderedStream().collect(Collectors.toList()));
            return factory;
        }

    }

    @Configuration(proxyBeanMethods = false)
    @ConditionalOnMissingBean(ReactiveWebServerFactory.class)
    @ConditionalOnClass({ org.eclipse.jetty.server.Server.class })
    static class EmbeddedJetty {

        @Bean
        @ConditionalOnMissingBean
        JettyResourceFactory jettyServerResourceFactory() {
            return new JettyResourceFactory();
        }

        @Bean
        JettyReactiveWebServerFactory jettyReactiveWebServerFactory(JettyResourceFactory resourceFactory,
                                                                    ObjectProvider<JettyServerCustomizer> serverCustomizers) {
            JettyReactiveWebServerFactory serverFactory = new JettyReactiveWebServerFactory();
            serverFactory.getServerCustomizers().addAll(serverCustomizers.orderedStream().collect(Collectors.toList()));
            serverFactory.setResourceFactory(resourceFactory);
            return serverFactory;
        }

    }

    @Configuration(proxyBeanMethods = false)
    @ConditionalOnMissingBean(ReactiveWebServerFactory.class)
    @ConditionalOnClass({ Undertow.class })
    static class EmbeddedUndertow {

        @Bean
        UndertowReactiveWebServerFactory undertowReactiveWebServerFactory(
            ObjectProvider<UndertowBuilderCustomizer> builderCustomizers) {
            UndertowReactiveWebServerFactory factory = new UndertowReactiveWebServerFactory();
            factory.getBuilderCustomizers().addAll(builderCustomizers.orderedStream().collect(Collectors.toList()));
            return factory;
        }
    }
}

它們生效的條件分別是：

• EmbeddedTomcat： @ConditionalOnClass -- Tomcat.class(apache)
• EmbeddedJetty： @ConditionalOnClass -- Server.class(jetty)
• EmbeddedUndertow： @ConditionalOnClass -- Undertow.class
• EmbeddedNetty： @ConditionalOnClass -- HttpServer.class

結合上面的依賴分析，spring-boot-starter-webflux 中依賴了 reactor-netty.jar，而 HttpServer.class 恰好在 reactor-netty.jar 包中，所以 netty 生效。最終使用 EmbeddedNetty 啟動服務。

6.參考

1. Spring Framework/WebFlux