springboot 使用webflux响应式开发教程(一)

什么是webFlux

springboot 使用webflux响应式开发教程(一)_第1张图片
左侧是传统的基于Servlet的Spring Web MVC框架,右侧是5.0版本新引入的基于Reactive Streams的Spring WebFlux框架,从上到下依次是Router FunctionsWebFluxReactive Streams三个新组件。

  • Router Functions: 对标@Controller,@RequestMapping等标准的Spring MVC注解,提供一套函数式风格的API,用于创建Router,Handler和Filter。
  • WebFlux: 核心组件,协调上下游各个组件提供响应式编程支持。
  • Reactive Streams: 一种支持背压(Backpressure)的异步数据流处理标准,主流实现有RxJava和Reactor,Spring WebFlux默认集成的是Reactor

在Web容器的选择上,Spring WebFlux既支持像Tomcat,Jetty这样的的传统容器(前提是支持Servlet 3.1 Non-Blocking IO API),又支持像Netty,Undertow那样的异步容器。不管是何种容器,Spring WebFlux都会将其输入输出流适配成Flux格式,以便进行统一处理。

值得一提的是,除了新的Router Functions接口,Spring WebFlux同时支持使用老的Spring MVC注解声明Reactive Controller。和传统的MVC Controller不同,Reactive Controller操作的是非阻塞的ServerHttpRequestServerHttpResponse,而不再是Spring MVC里的HttpServletRequestHttpServletResponse

 @GetMapping("/reactive/restaurants")
    public Flux findAll() {
        return restaurantRepository.findAll();
    }

可以看到主要变化就是在 返回的类型上Flux

Flux和Mono 是 Reactor 中的流数据类型,其中Flux会发送多次,Mono会发送0次或一次

使用webflux需要具备的基础是Reactive programming 的理解。 
Reactor 的基础 和 熟练的java8 lambda使用

创建springboot应用

下面通过创建股票报价的demo来演示。

通过 https://start.spring.io 或idea自带功能创建springboot项目,groupId为io.spring.workshop,artifactId为 stock-quotes。

springboot 使用webflux响应式开发教程(一)_第2张图片

勾选 ReactiveWeb

springboot 使用webflux响应式开发教程(一)_第3张图片

 

修改 application.properties 配置文件,指定接口 8081

 

server.port=8081

启动应用,成功后控制台输出日志

日志显示使用Netty而不是tomcat,后续会使用Tomcat

股票报价生成

 

 

定义实体

@Data
public class Quote {

    private static final MathContext MATH_CONTEXT = new MathContext(2);

    private String ticker;

    private BigDecimal price;

    private Instant instant;

    public Quote() {
    }

    public Quote(String ticker, BigDecimal price) {
        this.ticker = ticker;
        this.price = price;
    }

    public Quote(String ticker, Double price) {
        this(ticker, new BigDecimal(price, MATH_CONTEXT));
    }

    @Override
    public String toString() {
        return "Quote{" +
                "ticker='" + ticker + '\'' +
                ", price=" + price +
                ", instant=" + instant +
                '}';
    }
}

定义生成器

 

@Component
public class QuoteGenerator {

    private final MathContext mathContext = new MathContext(2);

    private final Random random = new Random();

    private final List prices = new ArrayList<>();

    /**
     * 生成行情数据
     */
    public QuoteGenerator() {
        this.prices.add(new Quote("CTXS", 82.26));
        this.prices.add(new Quote("DELL", 63.74));
        this.prices.add(new Quote("GOOG", 847.24));
        this.prices.add(new Quote("MSFT", 65.11));
        this.prices.add(new Quote("ORCL", 45.71));
        this.prices.add(new Quote("RHT", 84.29));
        this.prices.add(new Quote("VMW", 92.21));
    }


    public Flux fetchQuoteStream(Duration period) {

        // 需要周期生成值并返回,使用 Flux.interval
        return Flux.interval(period)
                // In case of back-pressure, drop events
                .onBackpressureDrop()
                // For each tick, generate a list of quotes
                .map(this::generateQuotes)
                // "flatten" that List into a Flux
                .flatMapIterable(quotes -> quotes)
                .log("io.spring.workshop.stockquotes");
    }

    /**
     * Create quotes for all tickers at a single instant.
     */
    private List generateQuotes(long interval) {
        final Instant instant = Instant.now();
        return prices.stream()
                .map(baseQuote -> {
                    BigDecimal priceChange = baseQuote.getPrice()
                            .multiply(new BigDecimal(0.05 * this.random.nextDouble()), this.mathContext);
                    Quote result = new Quote(baseQuote.getTicker(), baseQuote.getPrice().add(priceChange));
                    result.setInstant(instant);
                    return result;
                })
                .collect(Collectors.toList());
    }
}

使用webflux创建web应用

webflux的使用有两种方式,基于注解和函数式编程。这里使用函数式编程,先贴代码:

创建QuoteHandler

 

@Component
public class QuoteHandler {

    private final Flux quoteStream;

    public QuoteHandler(QuoteGenerator quoteGenerator) {
        this.quoteStream = quoteGenerator.fetchQuoteStream(ofMillis(1000)).share();
    }

    public Mono hello(ServerRequest request) {
        return ok().contentType(TEXT_PLAIN)
                .body(BodyInserters.fromObject("Hello Spring!"));
    }

    public Mono echo(ServerRequest request) {
        return ok().contentType(TEXT_PLAIN)
                .body(request.bodyToMono(String.class), String.class);
    }

    public Mono streamQuotes(ServerRequest request) {
        return ok()
                .contentType(APPLICATION_STREAM_JSON)
                .body(this.quoteStream, Quote.class);
    }

    public Mono fetchQuotes(ServerRequest request) {
        int size = Integer.parseInt(request.queryParam("size").orElse("10"));
        return ok()
                .contentType(APPLICATION_JSON)
                .body(this.quoteStream.take(size), Quote.class);
    }
}

创建Router

 

@Configuration
public class QuoteRouter {

   @Bean
   public RouterFunction route(QuoteHandler quoteHandler) {
      return RouterFunctions
            .route(GET("/hello").and(accept(TEXT_PLAIN)), quoteHandler::hello)
            .andRoute(POST("/echo").and(accept(TEXT_PLAIN).and(contentType(TEXT_PLAIN))), quoteHandler::echo)
            .andRoute(GET("/quotes").and(accept(APPLICATION_JSON)), quoteHandler::fetchQuotes)
            .andRoute(GET("/quotes").and(accept(APPLICATION_STREAM_JSON)), quoteHandler::streamQuotes);
   }
}

需要注意的是在springboot中Handler和Router都需要打上@Configuration。

HTTP请求交由Router转发给对应的Handler,Handler处理请求,并返回Mono,这里的Router类似@RequestMapping,Handler类似Controller。这么理解非常容易。

运行项目,浏览器输入 http://localhost:8081/hello 或者 使用curl,即可收到 "Hello Spring!"的文本信息。

到目前为止,一个简单的webflux示例已经完成,但是还没有体现出它与传统模式有何不同。

下面我们来做一下测试:

 

$ curl http://localhost:8081/echo -i -d "WebFlux workshop" -H "Content-Type: text/plain"
HTTP/1.1 200 OK
transfer-encoding: chunked
Content-Type: text/plain

WebFlux workshop

还是没有区别T.T,看下一步。

 

$ curl http://localhost:8081/quotes -i -H "Accept: application/stream+json"
HTTP/1.1 200 OK
transfer-encoding: chunked
Content-Type: application/stream+json

{"ticker":"CTXS","price":82.77,"instant":"2018-05-15T06:45:51.261Z"}
{"ticker":"DELL","price":64.83,"instant":"2018-05-15T06:45:51.261Z"}
{"ticker":"GOOG","price":881,"instant":"2018-05-15T06:45:51.261Z"}
{"ticker":"MSFT","price":67.3,"instant":"2018-05-15T06:45:51.261Z"}
{"ticker":"ORCL","price":48.1,"instant":"2018-05-15T06:45:51.261Z"}
{"ticker":"RHT","price":85.1,"instant":"2018-05-15T06:45:51.261Z"}
{"ticker":"VMW","price":92.24,"instant":"2018-05-15T06:45:51.261Z"}-------------------------------无敌分割线-------------------------------------
{"ticker":"CTXS","price":85.7,"instant":"2018-05-15T06:45:52.260Z"}
{"ticker":"DELL","price":64.12,"instant":"2018-05-15T06:45:52.260Z"}
{"ticker":"GOOG","price":879,"instant":"2018-05-15T06:45:52.260Z"}
{"ticker":"MSFT","price":67.9,"instant":"2018-05-15T06:45:52.260Z"}
{"ticker":"ORCL","price":46.43,"instant":"2018-05-15T06:45:52.260Z"}
{"ticker":"RHT","price":86.8,"instant":"2018-05-15T06:45:52.260Z"}...

 

上面的分割线是为了易于分辨人为加上去的,我们看到返回结果每隔一秒刷新一次,不终止的话会一直返回数据,传统的Request/Response是一次请求,一次返回。

注意是设置了Header Accept: application/stream+json ,

如果将Header设置为 Accept: application/json ,只会得到一次Response。

写测试

springboot的test模块包含WebTestClient,可以用来对webflux服务端进行测试。

 

@RunWith(SpringRunner.class)
//  We create a `@SpringBootTest`, starting an actual server on a `RANDOM_PORT`
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class StockQuotesApplicationTests {

   // Spring Boot will create a `WebTestClient` for you,
   // already configure and ready to issue requests against "localhost:RANDOM_PORT"
   @Autowired
   private WebTestClient webTestClient;

   @Test
   public void fetchQuotes() {
      webTestClient
            // We then create a GET request to test an endpoint
            .get().uri("/quotes?size=20")
            .accept(MediaType.APPLICATION_JSON)
            .exchange()
            // and use the dedicated DSL to test assertions against the response
            .expectStatus().isOk()
            .expectHeader().contentType(MediaType.APPLICATION_JSON)
            .expectBodyList(Quote.class)
            .hasSize(20)
            // Here we check that all Quotes have a positive price value
            .consumeWith(allQuotes ->
                  assertThat(allQuotes.getResponseBody())
                        .allSatisfy(quote -> assertThat(quote.getPrice()).isPositive()));
   }

   @Test
   public void fetchQuotesAsStream() {
      List result = webTestClient
            // We then create a GET request to test an endpoint
            .get().uri("/quotes")
            // this time, accepting "application/stream+json"
            .accept(MediaType.APPLICATION_STREAM_JSON)
            .exchange()
            // and use the dedicated DSL to test assertions against the response
            .expectStatus().isOk()
            .expectHeader().contentType(MediaType.APPLICATION_STREAM_JSON)
            .returnResult(Quote.class)
            .getResponseBody()
            .take(30)
            .collectList()
            .block();

      assertThat(result).allSatisfy(quote -> assertThat(quote.getPrice()).isPositive());
   }
}

后续期待更多精彩(二)

参考文章:

https://docs.spring.io/spring-framework/docs/5.0.3.RELEASE/spring-framework-reference/web.html#web-reactive-server-functional
http://projectreactor.io/docs
https://www.ibm.com/developerworks/cn/java/spring5-webflux-reactive/index.html
https://blog.csdn.net/qq_34438958/article/details/78539234

 

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