Spring Cloud Eureka 注册与发现操作步骤详解

在搭建Spring Cloud Eureka环境前先要了解整个架构的组成，常用的基础模式如下图：

服务提供者：将springboot服务编写好以后，通过配置注册中心地址方式注册，提供给消费者使用。
注册中心：服务的中间桥梁，服务提供者将服务注册。服务消费者可以通过注册信息调用需要使用的服务。
服务消费者：通过规定的调用方式，读取注册中心的注册信息，调用相应的服务。

根据后续的服务复杂度进化以后，可以看到服务提供者也可以是服务消费者，服务消费者也可以是服务提供者。根据不同的业务情况是可以互相调用的。

下面来搭建一个基础的eureka。环境还是使用的之前的spring官方下载的。

内容写的比较详细，可以跟这一步步操作。

一、注册中心

以下是几个需要修改和添加的地方，后面会有完整的pom.xml

<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.1.3.RELEASE</version>
		<relativePath /> <!-- lookup parent from repository -->
	</parent>
	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>Finchley.SR2</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>
<!-- 最新版的 eureka 服务端包 -->
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
		</dependency>

		<!-- 监控管理 -->
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-actuator</artifactId>
		</dependency>

这里采用Finchley.SR2版本 springboot版本改成 2.1.3.RELEASE

完整的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>2.1.3.RELEASE</version>
		<relativePath /> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.example</groupId>
	<artifactId>eureka1</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>eureka1</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
	</properties>
	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>Finchley.SR2</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter</artifactId>
		</dependency>
		<!-- 最新版的 eureka 服务端包 -->
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
		</dependency>

		<!-- 监控管理 -->
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-actuator</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
			<exclusions>
				<exclusion>
					<groupId>org.junit.vintage</groupId>
					<artifactId>junit-vintage-engine</artifactId>
				</exclusion>
			</exclusions>
		</dependency>
	</dependencies>

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

</project>

package com.example.demo;

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

@EnableEurekaServer
@SpringBootApplication
public class Eureka1Application {

	public static void main(String[] args) {
		SpringApplication.run(Eureka1Application.class, args);
	}

}

然后在代码文件中添加@EnableEurekaServer注解

修改application.yml文件

server:
 port: 3000 # 端口
eureka:
 instance:
 hostname: eureka-center
 appname: 注册中心
 client:
 registerWithEureka: false # 单点的时候设置为 false 禁止注册自身
 fetchRegistry: false
 serviceUrl:
 defaultZone: http://localhost:3000/eureka
 server:
 enableSelfPreservation: false
 evictionIntervalTimerInMs: 4000

启动服务

浏览器输入 http://127.0.0.1:3000

证明注册中心搭建成功了

二、服务提供者

前面的步骤一样

ProviderController是新建的一个服务代码

<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<!-- eureka 客户端 -->
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
		</dependency>

不同的地方有加了一个spring-boot-starter-web和spring-cloud-starter-netflix-eureka-client客户端
完整的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>2.1.3.RELEASE</version>
		<relativePath /> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.example</groupId>
	<artifactId>eurekaClient1</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>eurekaClient1</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
	</properties>
	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>Finchley.SR2</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<!-- eureka 客户端 -->
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
		</dependency>
	</dependencies>

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

</project>

EurekaClient1Application

package com.example.demo;

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

@EnableEurekaClient
@SpringBootApplication
public class EurekaClient1Application {

	public static void main(String[] args) {
		SpringApplication.run(EurekaClient1Application.class, args);
	}

}

ProviderController

package com.example.demo;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class ProviderController {

 @RequestMapping(value = "/hello")
 public String hello(){

 return "hello spring cloud!";
 }

 @RequestMapping(value = "/nice")
 public String nice(){

 return "nice to meet you!";
 }
}

application.yml

server:
 port: 3001

eureka:
 instance:
 preferIpAddress: true
 client:
 serviceUrl:
 defaultZone: http://localhost:3000/eureka ## 注册到 eureka
spring:
 application:
 name: single-provider ## 应用程序名称，后面会在消费者中用到

http://127.0.0.1:3001/hello

http://127.0.0.1:3000/

证明服务已经注册成功

三、服务消费者

前面还是同上

<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-openfeign</artifactId>
		</dependency>
		<!-- eureka 客户端 -->
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
		</dependency>

pom.xml新增以上内容

完整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>2.1.3.RELEASE</version>
		<relativePath /> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.example</groupId>
	<artifactId>eurekaClient1</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>eurekaClient1</name>
	<description>Demo project for Spring Boot</description>

	<properties>
		<java.version>1.8</java.version>
	</properties>
	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>Finchley.SR2</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-openfeign</artifactId>
		</dependency>
		<!-- eureka 客户端 -->
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
		</dependency>
	</dependencies>

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

</project>

EurekaClient2Application

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@EnableEurekaClient
@EnableFeignClients
@SpringBootApplication
public class EurekaClient2Application {

	/**
 * 注入 RestTemplate
 * 并用 @LoadBalanced 注解，用负载均衡策略请求服务提供者
 * 这是 Spring Ribbon 的提供的能力
 * @return
 */
 @LoadBalanced
 @Bean
 public RestTemplate restTemplate() {
 return new RestTemplate(); //用于调用服务对象
 }

	public static void main(String[] args) {
		SpringApplication.run(EurekaClient2Application.class, args);
	}

}

ConsumerController

package com.example.demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
public class ConsumerController {
	@Autowired
 private RestTemplate restTemplate;

 private static final String applicationName = "single-provider";//服务注册名

 @RequestMapping(value = "commonRequest")
 public Object commonRequest(){
 String url = "http://"+ applicationName +"/hello";
 String s = restTemplate.getForObject(url,String.class);//Ribbon方式调用服务
 return s;
 }
}

application.yml

server:
 port: 3002
eureka:
 client:
 serviceUrl:
 defaultZone: http://127.0.0.1:3000/eureka ## 注册到 eureka
 instance:
 preferIpAddress: true
spring:
 application:
 name: single-customer

启动服务
http://127.0.0.1:3002/commonRequest

返回服务提供者的 hello方法参数。

整个最简单的过程就完成了，需要更好的使用spring cloud 后续需要了解分布式、负载均衡、熔断等概念。在后续章节将一步步的拆分。

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