Eureka是用于服務(wù)注冊和發(fā)現(xiàn)的組件。主要分為Eureka Server服務(wù)注冊中心和Eureka Client客戶端。
Eureka是Spring Cloud首選推薦的服務(wù)注冊與發(fā)現(xiàn)組件,與Spring Cloud其他的組件可以無縫對接,服務(wù)的消費基本流程是:
1.首先需要有一個服務(wù)注冊中心Eureka Server;
2.然后服務(wù)提供者Eureka Client向服務(wù)注冊中心Eureka Server注冊,將自己的信息(主要是服務(wù)名和IP地址)通過REST API的形式提交給服務(wù)注冊中心Eureka Server;
3.同樣的,服務(wù)的消費者Eureka Client也會向服務(wù)注冊中心注冊,同時服務(wù)的消費者會獲取到一份服務(wù)注冊表的信息,該列表中包含了所有向服務(wù)注冊中心Eureka Server注冊的服務(wù)信息;
4.消費者獲取到服務(wù)注冊信息之后,就知道了服務(wù)提供者的IP地址,可以通過Http遠(yuǎn)程調(diào)度進行服務(wù)消費。
學(xué)習(xí)Eureka之前要搞清楚何為注冊中心,其實簡單來說,就是一個存儲服務(wù)的一些基本信息的一個容器,當(dāng)一個服務(wù)希望能夠被調(diào)用,那么就得將服務(wù)的一些基本信息注冊到這個注冊中心,這樣別的服務(wù)就可以在注冊中心中查詢到希望調(diào)用的服務(wù)的信息,從而實現(xiàn)服務(wù)發(fā)現(xiàn)。
下面就是我自己學(xué)習(xí)Spring Cloud時寫的demo,本實例使用的springBoot版本是2.0.3.RELEASE,springCloud的版本是Finchley.RELEASE:
創(chuàng)建服務(wù)注冊中心
這里需要使用IDEA工具構(gòu)建Maven多模塊項目,至于具體如何構(gòu)建Maven多模塊項目這里就不贅述了,詳細(xì)可以參考這篇博客
IntelliJ IDEA中創(chuàng)建Maven多模塊項目
- 創(chuàng)建一個Maven主工程
創(chuàng)建完工程之后,在父工程的pom文件中引入對應(yīng)的依賴,之后建的子model工程繼承該pom文件
<?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.chai.mysc</groupId>
<artifactId>springCloudDemo</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>pom</packaging>
<name>springCloudDemo</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.3.RELEASE</version>
<relativePath/>
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<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-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
- 創(chuàng)建服務(wù)注冊中心,即Eureka Server
創(chuàng)建完server端之后的pom文件為:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.4.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>demo1</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>eureka-server</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Greenwich.SR1</spring-cloud.version>
</properties>
<dependencies>
<!--注冊中心-->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</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>
</project>
在pom文件中引入需要的依賴之后,需要在spring boot工程的啟動類上加@EnableEurekaServer注解
package com.example.demo1;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {
public static void main(String[] args) {
SpringApplication.run(EurekaServerApplication.class, args);
}
}
由于Eureka Server本質(zhì)上也是一個eureka client,所以就必須要指定一個server。這就需要在對應(yīng)的配置文件application.yml中進行修改,用eureka.client.registerWithEureka: false和fetchRegistry: false來表明是一個server:
# 端口號
server:
port: 8761
eureka:
instance:
hostname: localhost
client:
registerWithEureka: false
fetchRegistry: false
serviceUrl:
defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
spring:
application:
name: eurka-server
這樣,服務(wù)注冊中心就創(chuàng)建完成了
- 創(chuàng)建服務(wù)提供者
創(chuàng)建的流程基本和上述的一致。
創(chuàng)建完之后的pom文件:
<?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>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.4.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>eureka-client</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Greenwich.SR1</spring-cloud.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
<version>2.0.0.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-test</artifactId>
<version>5.1.6.RELEASE</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
使用注解@EnableEurekaClient聲明是一個client
package com.example.demo;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
@SpringBootApplication
@EnableEurekaClient
@RestController
public class EurekaClientApplication {
public static void main(String[] args) {
SpringApplication.run(EurekaClientApplication.class, args);
}
@Value("${server.port}")
String port;
@RequestMapping("/hi")
public String home(@RequestParam(value = "name", defaultValue = "chaiminquan") String name) {
return "hi" + name + ",i am from prot:" +port;
}
}
然后再配置文件中配置對應(yīng)的服務(wù)注冊中心的地址:
server:
port: 8762
spring:
application:
name: eureka-client
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8761/eureka/
在配置文件中的spring.application.name的是服務(wù)名,這是之后服務(wù)與服務(wù)之間調(diào)用需要用到的。
啟動工程之后,訪問服務(wù)注冊中心地址,就可以看到新建的服務(wù)已經(jīng)注冊成功了!

Demo地址
參考資料
方志朋.《深入理解Spring Cloud與微服務(wù)構(gòu)建》.北京:人民郵電出版社,2018.03