SpringCloud：服務註冊與發現（Eureka）

1、Eureka簡介
Eureka是一個服務註冊與發現組件，主要有兩部分組成：註冊中心（Eureka-Server）和服務提供端（Eureka-Client），Eureka-Server通過一個註冊表維護了所有向Eureka-Server註冊的Eureka-Client的主機地址和端口等信息，同時Eureka-Client可以向Eureka-Server獲取該註冊表，並默認每30s向註冊中心發送一次心跳錶明自己還活着，如果Eureka-Server在一定時間內未接收某個微服務實例的心跳，EurekaServer將會註銷該實例（默認90s）。

2、創建一個SpringBoot項目作爲Eureka-Server
創建過程就不多說了，需要注意的是SpringBoot的版本號和SpringCloud的版本號要對應，不然無法找到@EnableEurekaServer和@EnableEurekaClien註解，這兩個註解是必須要用上的，我這裏springboot版本是2.0.3.RELEASE，springcloud版本是Finchley.RELEASE，本系列文章都是使用這兩個版本，pom文件如下：

<?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>2.0.3.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.example</groupId>
	<artifactId>eureka-server</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>eureka-server</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
		<spring-cloud.version>Finchley.RELEASE</spring-cloud.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
		</dependency>

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

	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>Finchley.RELEASE</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

	<repositories>
		<repository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
		</repository>
	</repositories>

</project>

3、修改配置文件application.yml，該文件默認後綴是.properties,我這裏用的是yml後綴的，個人感覺層次感更好些吧

server:
  port: 8000   #使用的端口

eureka:
  instance:
    hostname: localhost #所在機器地址
  client:
    registerWithEureka: false  #表明是個註冊中心
    fetchRegister: false  #表明是個註冊中心
    serviceUrl:  #聲明註冊中心的地址（其實就是自己），其實每個Server都是一個Client
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/

spring:
  application:
    name: eureka-server  #該實例名稱

4、使用@EnableEurekaServer，並啓動

@EnableEurekaServer
@SpringBootApplication
public class EurekaServerApplication {

	public static void main(String[] args) {
		SpringApplication.run(EurekaServerApplication.class, args);
	}

}

5、打開註冊種web界面：localhost:8000，這時候一個註冊的服務實例都沒有

6、創建一個SpringBoot項目作爲Eureka-Client
就不多廢話了，直接上代碼，其實跟Eureka-Server差不多，只是配置文件和pom文件有點區別
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>2.0.3.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.example</groupId>
	<artifactId>eureka-client1</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>eureka-client1</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
		<spring-cloud.version>Finchley.RELEASE</spring-cloud.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
		</dependency>

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

	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>Finchley.RELEASE</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

	<repositories>
		<repository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/milestone</url>
		</repository>
	</repositories>

</project>

application.yml:

server:
  port: 8001

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8000/eureka

spring:
  application:
    name: eureka-client1

7、寫個接口並啓動

/**
 * @author XuJD
 * @create 2019-11-22 14:07
 **/
@EnableEurekaClient
@RestController
@RequestMapping("serviceTest")
public class ServiceController {

    @Value("${server.port}")
    public String port;


    @RequestMapping("/test")
    public String test(){
        return "Hello world,this is eureka-client1--"+port;
    }
}

這個時候可以看到這個Eureka-Client1實例已經註冊到Eureka-Server中了

代碼地址：https://github.com/xujiangdong/SpringCloud_Study

都看到這裏了，點個star支持下吧，萬分感謝！