Spring Cloud Netflix 之 Eureka

#Spring Cloud Netflix 之 Eureka

前言

Eureka 是 Netflix 公司开发的一款开源的服务注册与发现组件。 Spring Cloud 使用 Spring Boot 思想为 Eureka 增加了自动化配置，开发人员只需要引入相关依赖和注解，就能将 Spring Boot 构建的微服务轻松地与 Eureka 进行整合。

1、Eureka 两大组件

Eureka 采用 CS（Client/Server，客户端/服务器） 架构，它包括以下两大组件：Eureka Server、Eureka Client

|组件|介绍
|------
|Eureka Server|Eureka 服务注册中心，主要用于提供服务注册功能
|Eureka Client|Eureka 客户端，通常指的是微服务系统中各个微服务

2、Eureka 服务注册与发现

|功能|介绍
|------
|服务注册中心（Register Service）|它是一个 Eureka Server，用于提供服务注册和发现功能。
|服务提供者（Provider Service）|它是一个 Eureka Client，用于提供服务。它将自己提供的服务注册到服务注册中心，以供服务消费者发现。
|服务消费者（Consumer Service）|它是一个 Eureka Client，用于消费服务。它可以从服务注册中心获取服务列表，调用所需的服务。

3、案例

3.1、创建主工程

名称：SpringCloud

3.1.1、主工程pom.xml配置

<?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>
   <packaging>pom</packaging>
   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>2.6.13</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.hqyj</groupId>
   <artifactId>drp</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <name>drp-parent</name>
   <description>Demo project for Spring Boot</description>
   <properties>
      <maven.compiler.source>8</maven.compiler.source>
      <maven.compiler.target>8</maven.compiler.target>
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <maven.compiler.source>1.8</maven.compiler.source>
      <maven.compiler.target>1.8</maven.compiler.target>
      <junit.version>4.12</junit.version>
      <log4j.version>1.2.17</log4j.version>
      <lombok.version>1.16.18</lombok.version>
   </properties>
   <dependencyManagement>
      <dependencies>
         <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>2021.0.5</version>
            <type>pom</type>
            <scope>import</scope>
         </dependency>
      </dependencies>
   </dependencyManagement>

   <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.5.1</version>
                <configuration>
                    <source>${maven.compiler.source}</source>
                    <target>${maven.compiler.target}</target>
                </configuration>
            </plugin>
        </plugins>

    </build>

</project>

3.2、创建子公共模块common-api

3.2.1、添加module

3.2.2、pom.xml配置

<?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>com.hqyj</groupId>
        <artifactId>SpringCloud</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>

    <artifactId>common-api</artifactId>

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

    <dependencies>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
    </dependencies>

</project>

3.2.3、maven非springboot项目，增加main入口

添加Main.java，指定main入口，防止Maven package / install打包失败

public class Main {<!-- -->
    public static void main(String[] args) {<!-- -->
        System.out.println("common-api");
    }

}

3.3、创建Eureka注册中心模块eureka-server

3.3.1、配置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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>com.hqyj</groupId>
        <artifactId>SpringCloud</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>

    <artifactId>eureka-server</artifactId>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <skip-tests>true</skip-tests>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>com.github.enesusta</groupId>
            <artifactId>spring-devtools</artifactId>
            <version>1.0.1</version>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>

    </dependencies>
    
</project>

3.3.2、配置application.yml

在resource目录下，新建application.yml文件 编辑application.yml文件，添加eureka配置

server:
  port: 7001

eureka:
  instance:
    hostname: localhost #eureka服务端的实例名称，
  client:
    register-with-eureka: false #false表示不向注册中心注册自己。
    fetch-registry: false #false表示自己端就是注册中心，我的职责就是维护服务实例，并不需要去检索服务
    service-url:
      defaultZone: http://${<!-- -->eureka.instance.hostname}:${<!-- -->server.port}/eureka/ #单机版服务注册中心

3.3.3、启动eureka-server

创建EurekaServerApplication.java启动文件

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);
    }
}

3.3.3.1、编译eureka-server

3.3.3.2、运行EurekaServerApplication.java文件

启动：

3.4、创建用户服务模块user-service

3.4.1、配置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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>com.hqyj</groupId>
        <artifactId>SpringCloud</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>

    <artifactId>user-service</artifactId>

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

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!--devtools 开发工具-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <!--Spring Boot 测试-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!--junit 测试-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <!-- 修改后立即生效，热部署 -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>springloaded</artifactId>
            <version>1.2.8.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>com.hqyj</groupId>
            <artifactId>common-api</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>
    </dependencies>

</project>

3.4.2、配置application.yml

server:
  port: 8001
spring:
  application:
    name: user-service  #微服务名称
eureka:
  client: #将客户端注册到 eureka 服务列表内
    service-url:
      defaultZone: http://localhost:7001/eureka  #这个地址是 7001注册中心在 application.yml 中暴露出来额注册地址 （单机版）

3.4.3、启动user-service

创建UserApplication.java启动文件

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

@SpringBootApplication
@EnableDiscoveryClient
public class UserApplication {<!-- -->
    public static void main(String[] args) {<!-- -->
        SpringApplication.run(UserApplication.class,args);
    }
}

3.4.3.1、编译user-service

3.4.3.2、运行UserApplication.java文件

3.4.3.3、测试

3.5、查看编译后的包