前言

從本篇部落格開始將正式進入Spring Cloud的實戰部分，因為博主用了很長時間的Dubbo，並且Spring Cloud和Dubbo都是微服務框架，它們有很多相似之處，所以可能在部落格中提及進行類比，如果沒有接觸過Dubbo的朋友直接略過該部分內容即可，大可不必糾結

在微服務架構中服務治理可以說是最核心和基礎的模組，它主要用來實現各個微服務例項的自動註冊和發現，在Dubbo中主要使用Zookeeper來進行服務間的協調，在Spring Cloud中Eureka則扮演著服務治理的角色(Sping Cloud也支援Zookeeper作為註冊中心方式，但不是最佳實踐，建議感興趣的朋友自行搜尋Zookeeper與Eureka的對比)

搭建服務註冊中心

新建一個基礎Spring Boot工程，在pom.xml匯入如下依賴

<?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>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.6.RELEASE</version>
        <relativePath/>
    </parent>

    <groupId>
 
com.roberto.springcloud</groupId>
    <artifactId>eureka-server</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <packaging>jar</packaging>

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

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Dalston.SR2</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>

啟動類新增@EnableEurekaServer註解

package com.roberto.springboot;

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

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

在application.yml下新增Eureka的配置

server:
  port: 8761
eureka:
  instance:
    hostname: localhost
  client:
    fetch-registry: false
    register-with-eureka: false
    serviceUrl:
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/

eureka.client.register-with-eureka 表示是否將自己註冊到Eureka Server，預設值為true，由於此處為單機版Eureka Server所以設定為false，表示不向註冊中心註冊自己

eureka.client.fetch-registry 表示是否從Eureka Server獲取註冊資訊，預設為true，因為這是一個單點的Eureka Server，不需要同步其他的Eureka Server節點的資料，故而設為false

eureka.client.serviceUrl.defaultZone 表示與Eureka Server互動的地址，查詢服務和註冊服務都需要依賴這個地址。預設是http://localhost:8761/eureka，多個地址可使用 , 分隔

建立父工程用於繼承

由於後續很多DEMO都要引入Spring Boot和Spring Cloud依賴，為了避免重複依賴並且為了統一管理版本號，此處新增父工程用於子模組繼承，父工程的pom.xml檔案如下

<?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.roberto.springcloud</groupId>
    <artifactId>spring-cloud-parent</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <packaging>pom</packaging>

    <modules>
        <module>spring-cloud-user-service</module>
        <module>spring-cloud-movie-service</module>
    </modules>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.6.RELEASE</version>
    </parent>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Dalston.SR2</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>

註冊服務提供者

新建子模組，pom.xml檔案定義如下

<?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>
        <artifactId>spring-cloud-parent</artifactId>
        <groupId>com.roberto.springcloud</groupId>
        <version>1.0.0-SNAPSHOT</version>
    </parent>

    <artifactId>spring-cloud-user-service</artifactId>

    <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>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>
    </dependencies>
</project>

新增啟動類新增@EnableEurekaClient註解

package com.roberto.springcloud;

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

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

Controller層

package com.roberto.springcloud.controller;

import com.roberto.springcloud.repository.UserRepository;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;

@RestController
public class UserController {
    private static final Logger LOGGER = LoggerFactory.getLogger(UserController.class);

    @Resource(name = "discoveryClient")
    private DiscoveryClient discoveryClient;

    @RequestMapping(value = "/hello", method = RequestMethod.GET)
    public String index() {
        ServiceInstance serviceInstance = discoveryClient.getLocalServiceInstance();
        LOGGER.info("/hello,host:" + serviceInstance.getHost() + ",service_id:" + serviceInstance.getServiceId());
        return "Hello World";
    }
}

修改配置檔案application.yml

spring:
  application:
    name: user-service
eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

spring.application.name 為服務命名
eureka.client.serviceUrl.defaultZone 指定註冊中心地址

啟動專案訪問Eureka資訊面板 發現user-service已經註冊成功

至此服務提供者已經建立成功

註冊服務消費者

新建子模組，pom.xml檔案定義如下

<?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>
        <artifactId>spring-cloud-parent</artifactId>
        <groupId>com.roberto.springcloud</groupId>
        <version>1.0.0-SNAPSHOT</version>
    </parent>

    <artifactId>spring-cloud-movie-service</artifactId>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

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

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-ribbon</artifactId>
        </dependency>
    </dependencies>
</project>

啟動類新增@EnableEurekaClient註解 並注入RestTemplate

package com.roberto.springcloud;

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.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@EnableEurekaClient
@SpringBootApplication
public class SpringCloudMovieService {
    @Bean
    @LoadBalanced
    RestTemplate restTemplate(){
        return new RestTemplate();
    }

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

Controller層

package com.roberto.springcloud.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import javax.annotation.Resource;

@RestController
public class MovieController {
    @Resource(name = "restTemplate")
    private RestTemplate restTemplate;

    @RequestMapping(value = "/index", method = RequestMethod.GET)
    public String index() {
        return restTemplate.getForEntity("http://user-service/hello", String.class).getBody();
    }
}

修改配置檔案application.yml

server:
  port: 9090
spring:
  application:
    name: movie-service
eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

至此服務消費者已經建立成功

Eureka高可用

在分散式環境中為了避免系統故障引發一系列問題，我們必須對各個元件進行高可用部署。Eureka的高可用實際就是將自己作為服務向其他註冊中心註冊自己，這樣就可以形成一組相互註冊的服務註冊中心，以實現服務清單的同步，達到高可用效果。由於機器數量限制本次搭建為Eureka的偽叢集

修改host檔案 新增如下配置

127.0.0.1       peer1 peer2 peer3

修改Eureka的application.yml檔案如下

spring:
  application:
    name: EUREKA-HA

---
server:
  port: 8761
spring:
  profiles: peer1
eureka:
  instance:
    hostname: peer1
  client:
    serviceUrl:
      defaultZone: http://peer2:8762/eureka/,http://peer3:8763/eureka/

---
server:
  port: 8762
spring:
  profiles: peer2
eureka:
  instance:
    hostname: peer2
  client:
    serviceUrl:
      defaultZone: http://peer1:8761/eureka/,http://peer3:8763/eureka/
---
server:
  port: 8763
spring:
  profiles: peer3
eureka:
  instance:
    hostname: peer3
  client:
    serviceUrl:
      defaultZone: http://peer1:8761/eureka/,http://peer2:8762/eureka/

新增啟動引數 分別啟動三個Eureka例項

-Dspring.profiles.active=peer

訪問Eureka資訊面板如下圖所示表明HA環境搭建成功

注:在HA環境下無需配置eureka.client.register-with-eureka與eureka.client.fetch-registry屬性 預設為true

Eureka的安全配置

為了服務註冊中心的安全考慮，很多時候我們都會為服務註冊中心加入安全校驗，過程如下

在pom.xml新增Security依賴

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-security</artifactId>
</dependency>

修改application.yml檔案 新增security配置

spring:
  application:
    name: EUREKA-HA

---
spring:
  profiles: peer1
server:
  port: 8761
security:
  basic:
    enabled: true
  user:
    name: roberto
    password: roberto123
eureka:
  instance:
    hostname: peer1
  client:
    serviceUrl:
      defaultZone: http://roberto:[email protected]:8762/eureka/,http://roberto:[email protected]:8763/eureka/

---
spring:
  profiles: peer2
server:
  port: 8762
security:
  basic:
    enabled: true
  user:
    name: roberto
    password: roberto123
eureka:
  instance:
    hostname: peer2
  client:
    serviceUrl:
      defaultZone: http://roberto:[email protected]:8761/eureka/,http://roberto:[email protected]:8763/eureka/

---
spring:
  profiles: peer3
server:
  port: 8763
security:
  basic:
    enabled: true
  user:
    name: roberto
    password: roberto123
eureka:
  instance:
    hostname: peer3
  client:
    serviceUrl:
      defaultZone: http://roberto:[email protected]:8761/eureka/,http://roberto:[email protected]:8762/eureka/

注:在配置serviceUrl時，需要在value值的URL中加入相應的安全校驗資訊，格式為http://<username>:<password>@hostname:port/eureka，其中username為使用者名稱，password為密碼，hostname為主機名或IP地址，port為埠號

其他服務例項連線到Eureka時可以通過如下配置進行授權

@Bean
public BasicAuthRequestInterceptor basicAuthRequestInterceptor() {
    return new BasicAuthRequestInterceptor("roberto", "roberto123");
}

自定義Eureka的Instance ID

在Spring Cloud中，服務的Instance ID的預設值是${spring.cloud.client.hostname}:${spring.application.name}:${spring.application.instance_id:${server.port}}，也就是機器主機名:應用名稱:應用埠 。因此在Eureka Server首頁中看到的服務的資訊類似如下:localhost:EUREKA-HA:8763，如需自定義該部分資訊只需在application.yml中新增如下配置

eureka:
  instance:
    preferIpAddress: true
    instance-id: ${spring.cloud.client.ipAddress}:${server.port}

Eureka配置屬性

Eureka涉及到的引數配置項數量眾多，詳細可參見Eureka配置屬性

Eureka配置所在類

org.springframework.cloud.netflix.eureka.EurekaInstanceConfigBean
org.springframework.cloud.netflix.eureka.EurekaClientConfigBean
org.springframework.cloud.netflix.eureka.server.EurekaServerConfigBean