Eureka：就是服务注册中心（可以是一个集群），对外暴露自己的地址
提供者：启动后向Eureka注册自己信息（地址，提供什么服务）
消费者：向Eureka订阅服务，Eureka会将对应服务的所有提供者地址列表发送给消费者，并且定期更新
心跳(续约)：提供者定期通过http方式向Eureka刷新自己的状态

一，最少依赖启动，依赖如下

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>org.example</groupId>
    <artifactId>Eureka-server</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.5.RELEASE</version>
        <relativePath/>
    </parent>

    <properties>
        <spring-cloud.version>Greenwich.SR1</spring-cloud.version>
    </properties>

    <dependencies>
        <!-- springCloud -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>${spring-cloud.version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
            <version>2.1.0.RELEASE</version>
        </dependency>
    </dependencies>

</project>

问题点：遇到了版本要兼容问题

application.yml

server:
  port: 8868
spring:
  application:
    # 应用名称，会在Eureka中作为服务的id标识（serviceId）
    name: eureka-server
eureka:
  client:
    # EurekaServer的地址，现在是自己的地址，如果是集群，需要写其它Server的地址。
    service-url:
      defaultZone: http://127.0.0.1:8868/eureka
    # 不注册自己
    register-with-eureka: false
    # 不拉取
    fetch-registry: false

启动类

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@EnableEurekaServer
@SpringBootApplication
public class EurekaApplication {
    public static void main(String[] args) {
        SpringApplication.run(EurekaApplication.class,args);
    }
}

启动

生产者项目中加入依赖

（1）pom文件

		<dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
            <version>2.1.0.RELEASE</version>
        </dependency>

（2）application.yaml文件

server:
  port: 8081
spring:
  datasource:
    username: root
    password: ROOT
    url: jdbc:mysql://localhost:3306/my_demo?serverTimezone=UTC
    driver-class-name: com.mysql.cj.jdbc.Driver
  application:
    name: permission-server
eureka:
  client:
    service-url:
      defaultZone: http://127.0.0.1:8868/eureka

（3）启动类加入注解

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
@SpringBootApplication
@MapperScan("com.w***n.it")
@EnableDiscoveryClient // 暴露到Eureka上
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class,args);
    }
}

消费者项目

同生产者一样，只有直接调用

		//获取eureka中注册的user-service实例列表
        List<ServiceInstance> instances = discoveryClient.getInstances("permission-server");
		
		ServiceInstance serviceInstance = instances.get(0);