一、前言

1、什麼是Eureka？

Eureka是Netflix開源的服務註冊與發現框架，Eureka由兩個元件組成：Eureka伺服器和Eureka客戶端。

Eureka Server提供服務註冊服務，各個節點啟動後，會在Eureka Server中進行註冊，這樣EurekaServer中的服務登錄檔中將會儲存所有可用服務節點的資訊，服務節點的資訊可以在介面中直觀的看到。

Eureka客戶端是一個Java客戶端，用來簡化與伺服器的互動、作為輪詢負載均衡器，並提供服務的故障切換支援。

2、Eureka概覽

3、本篇環境資訊

二、搭建Eureka Server

1、建立Eureka Server專案

• 建立一個Spring Boot工程

使用maven-archtype-quickstart模板建立專案

• 在pom.xml加入相關依賴

<?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>io.ken.springcloud.eurekaserver</groupId>
    <artifactId>eurekaserver</artifactId>
    <version>1.0-SNAPSHOT</version>

    <name>eurekaserver</name>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.RELEASE</version>
    </parent>

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

    <dependencies>

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

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <repositories>
        <repository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/libs-snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
    </repositories>

    <build>
        <finalName>eurekaserver</finalName>
    </build>

</project>

2、配置EurekaServer啟動類

修改\src\main\java\io\ken\springcloud\eurekaserver\App.java
基於Spring Boot建立啟動類，新增上 @EnableEurekaServer 註解

package io.ken.springcloud.eurekaserver;

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


@EnableEurekaServer
@SpringBootApplication
public class App {

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

3、配置Eureka Server

在\src\main下建立資料夾resources資料夾並設定為Resources Root

在resources資料夾下建立application.yml檔案並配置Eureka Server

server:
  port: 8800

spring:
  application:
    name: EurekaServer

eureka:
  client:
    registerWithEureka: false
    fetchRegistry: false
    serviceUrl:
      defaultZone: http://localhost:${server.port}/eureka/

Eureka預設會以客戶端來註冊自己，所以registerWithEureka、fetchRegistry要配置為false。

4、Eureka Server資訊預覽

啟動Eureka Server專案後，訪問：http://localhost:8800/ ，可以看到下面的頁面，其中還沒有發現任何服務。

三、搭建服務並註冊（Eureka Client）

1、建立Eureka Client專案

• 建立一個Spring Boot工程

使用maven-archtype-quickstart模板建立專案

• 在pom.xml加入相關依賴

<?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>io.ken.springcloud.helloservice</groupId>
    <artifactId>helloservice</artifactId>
    <version>1.0-SNAPSHOT</version>

    <name>helloservice</name>
    <url>http://ken.io</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.RELEASE</version>
    </parent>

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

    <dependencies>

        <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-web</artifactId>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <repositories>
        <repository>
            <id>spring-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/libs-snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
    </repositories>

    <build>
        <finalName>helloservice</finalName>
    </build>

</project>

2、配置Eureka Client啟動類

修改\src\main\java\io\ken\springcloud\helloservice\App.java
基於Spring Boot建立啟動類，新增上 @EnableDiscoveryClient 註解

package io.ken.springcloud.helloservice;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

@EnableDiscoveryClient
@SpringBootApplication
public class App {

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

3、建立測試服務

在\src\main\java\io\ken\springcloud\helloservice建立package：controller
然後建立HelloController.java

package io.ken.springcloud.helloservice.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {

    @Autowired
    DiscoveryClient discoveryClient;

    @RequestMapping("/")
    public Object index() {
        return "hello service";
    }

    @RequestMapping("/info")
    public Object info() {
        return discoveryClient.getServices();
    }
}

4、配置Eureka Client

在\src\main下建立資料夾resources資料夾並設定為Resources Root

在resources資料夾下建立application.yml檔案並配置Eureka Client

server:
  port: 8601

spring:
  application:
    name: helloservice

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8800/eureka/

5、服務註冊&訪問測試

HelloService專案成功啟動後，訪問 http://localhost:8601 ,或者 http://localhost:8601/info
檢視是否正常啟動

訪問 http://localhost:8800 ，會發現服務已註冊

搞定！

四、備註

• 本篇示例程式碼

https://github.com/ken-io/springcloud-course/tree/master/chapter-01