Spring Boot ApplicationReadyEvent 教程 · ZetCode 中文系列教程

# Spring Boot `ApplicationReadyEvent` 教程 > 原文： [http://zetcode.com/springboot/applicationreadyevent/](http://zetcode.com/springboot/applicationreadyevent/) Spring Boot `ApplicationReadyEvent`教程展示了在应用就绪后如何执行任务。 Spring Boot 应用发出各种事件。我们可以使用监听器对此类事件做出反应。例如，`ApplicationStartedEvent`是在刷新上下文之后但在调用任何应用和命令行运行程序之前发送的。在调用任何应用和命令行运行程序之后，将发送`ApplicationReadyEvent`。它指示该应用已准备就绪，可以处理请求。 ## Spring Boot `ApplicationReadyEvent`示例以下 Spring Boot 应用是一个简单的 Web 应用，可响应`ApplicationStartedEvent`触发 Web 请求。该请求是通过`WebClient`发出的。 ```java pom.xml src ├───main │ ├───java │ │ └───com │ │ └───zetcode │ │ │ Application.java │ │ ├───bean │ │ │ TimeResponse.java │ │ ├───event │ │ │ AppEvents.java │ │ └───routes │ │ AppRoutes.java │ └───resources └───test └───java └───com └───zetcode └───routes AppRoutesTest.java ``` 这是项目结构。 `pom.xml` ```java <?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 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.zetcode</groupId> <artifactId>applicationreadyevent</artifactId> <version>1.0-SNAPSHOT</version> <packaging>jar</packaging> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>11</maven.compiler.source> <maven.compiler.target>11</maven.compiler.target> </properties> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.1.5.RELEASE</version> </parent> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-webflux</artifactId> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project> ``` 这是 Maven 构建文件。 `spring-boot-starter-webflux`是使用 Spring Framework 的反应式 Web 支持构建 WebFlux 应用的入门。 `com/zetcode/bean/TimeResponse.java` ```java package com.zetcode.bean; public class TimeResponse { private String date; private Long unixtime; private String time; public String getDate() { return date; } public void setDate(String date) { this.date = date; } public Long getUnixtime() { return unixtime; } public void setUnixtime(Long unixtime) { this.unixtime = unixtime; } public String getTime() { return time; } public void setTime(String time) { this.time = time; } @Override public String toString() { final StringBuilder sb = new StringBuilder("TimeResponse{"); sb.append("date='").append(date).append('\''); sb.append(", unixtime=").append(unixtime); sb.append(", time='").append(time).append('\''); sb.append('}'); return sb.toString(); } } ``` 这是`TimeResponse` bean。它用于存储来自 Web 请求的数据。 `com/zetcode/event/AppEvents.java` ```java package com.zetcode.event; import com.zetcode.bean.TimeResponse; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.boot.context.event.ApplicationReadyEvent; import org.springframework.context.event.EventListener; import org.springframework.stereotype.Component; import org.springframework.web.reactive.function.client.WebClient; import reactor.core.publisher.Mono; @Component public class AppEvents { private static final Logger logger = LoggerFactory.getLogger(AppEvents.class); @EventListener(ApplicationReadyEvent.class) public void startApp() { var webClient = WebClient.create("http://time.jsontest.com/"); Mono<TimeResponse> result = webClient.get() .retrieve() .bodyToMono(TimeResponse.class); result.subscribe(res -> logger.info("{}", res)); } } ``` 在`AppEvents`中，我们创建了一个简单的 GET 请求。 ```java @EventListener(ApplicationReadyEvent.class) public void startApp() { ``` 使用`@EventListener`注解，我们注册`ApplicationReadyEvent`。 ```java var webClient = WebClient.create("http://time.jsontest.com/"); ``` 从`http://time.jsontest.com/`中，我们可以获得当前时间。 ```java Mono<TimeResponse> result = webClient.get() .retrieve() .bodyToMono(TimeResponse.class); result.subscribe(res -> logger.info("{}", res)); ``` 使用`WebClient`，我们向站点创建一个 GET 请求，并将结果输出到终端。 `com/zetcode/routes/AppRoutes.java` ```java package com.zetcode.routes; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.web.reactive.function.server.RouterFunction; import org.springframework.web.reactive.function.server.ServerResponse; import static org.springframework.web.reactive.function.server.RequestPredicates.GET; import static org.springframework.web.reactive.function.server.RouterFunctions.route; import static org.springframework.web.reactive.function.server.ServerResponse.ok; @Configuration public class AppRoutes { @Bean RouterFunction<ServerResponse> home() { return route(GET("/"), request -> ok().syncBody("Home page")); } } ``` 我们的应用使用函数式的 Web 框架来返回首页的简单消息。 `com/zetcode/Application.java` ```java package com.zetcode; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.boot.web.servlet.support.SpringBootServletInitializer; @SpringBootApplication public class Application extends SpringBootServletInitializer { public static void main(String[] args) { SpringApplication.run(Application.class, args); } } ``` `Application`设置 Spring Boot 应用 `com/zetcode/routes/AppRoutesTest.java` ```java package com.zetcode.routes; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.context.SpringBootTest; import org.springframework.test.context.junit4.SpringRunner; import org.springframework.test.web.reactive.server.WebTestClient; @RunWith(SpringRunner.class) @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT) public class AppRoutesTest { @Autowired private WebTestClient client; @Test public void test_home_page() { client.get().uri("/").exchange().expectStatus().isOk() .expectBody(String.class).isEqualTo("Home page"); } } ``` 使用`WebTestClient`，我们为主页创建一种测试方法。 ```java ... 2019-06-21 16:40:45.214 INFO 9356 --- [ctor-http-nio-5] com.zetcode.event.AppEvents : TimeResponse{date='06-21-2019', unixtime=null, time='02:40:47 PM'} ... ``` 当应用启动时，我们将此消息发送到终端。列出[所有 Spring Boot 教程](/all/#springboot)。