第十四章：（3）Spring Boot 与 分布式 之 SpringCloud

一、Eureka 注册中心

　　1、pom.xml 配置文件

<?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 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>2.6.2</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.njf</groupId>
    <artifactId>spring-boot-14-springcloud-eureka-server</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>spring-boot-14-springcloud-eureka-server</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>2021.0.0</spring-cloud.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</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>

　　2、配置 Eureka 信息

　　　　在application.yml 中配置 Eureka 的信息

server:
  port: 8761

eureka:
  instance:
    hostname: eureka-server #eureka 实例的主机名

  client:
    register-with-eureka: false  #不把eureka自己注册到eureka中
    fetch-registry: false        #不从eureka上获取服务的注册信息
    service-url:   #注册中心地址，服务注册地址
      defaultZone: http://localhost:8761/eureka

　　3、使用 @EnableEurekaServer 启动 EurekaServer 注册中心

/**
 * 注册中心
 * 1、配置 Eureka 信息
 * 2、@EnableEurekaServer 启动 EurekaServer 注册中心
 */
@EnableEurekaServer
@SpringBootApplication
public class SpringBoot14SpringcloudEurekaServerApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringBoot14SpringcloudEurekaServerApplication.class, args);
    }

}

　　4、启动注册中心

　　可以看到，现在还没有任何可用的应用服务。 

二、创建服务提供者，并注册

　　1、pom.xml 配置文件

<?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 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>2.6.2</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.njf</groupId>
    <artifactId>spring-boot-14-springcloud-provider</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>spring-boot-14-springcloud-provider</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>2021.0.0</spring-cloud.version>
    </properties>
    <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>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</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>

　　2、配置 Eureka 信息

server:
  port: 8002

spring:
  application:
    name: provider-ticket

eureka:
  instance:
    prefer-ip-address: true   #注册服务的时候使用服务的 ip 地址进行注册

  client:
    service-url: #注册中心地址，服务注册地址
      defaultZone: http://localhost:8761/eureka

　　3、提供服务

　　　　TicketService：

@Service
public class TicketService {

    public String getTicket() {
        System.out.println("8002");
        return "《厉害了，我的国！》";
    }
}

　　　　TicketController：

@RestController
public class TicketController {


    @Autowired
    TicketService ticketService;

    @GetMapping(value = "/ticket")
    public String getTicket() {
        return ticketService.getTicket();
    }
}

　　4、将服务提供者分别打成两个jar包，端口分别为：8001与8002

　　　　

　　5、启动这两个服务，会注册到注册中心中

三、创建服务消费者，并注册

　　1、pom.xml 配置文件

<?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 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>2.6.2</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.njf</groupId>
    <artifactId>spring-boot-14-springcloud-consumer</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>spring-boot-14-springcloud-consumer</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>2021.0.0</spring-cloud.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <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-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</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>

　　2、配置 Eureka 信息

server:
  port: 8200

spring:
  application:
    name: consomer-user

eureka:
  instance:
    prefer-ip-address: true   #注册服务的时候使用服务的 ip 地址进行注册

  client:
    service-url: #注册中心地址，服务注册地址
      defaultZone: http://localhost:8761/eureka

　　

　　3、开启服务发现

@EnableDiscoveryClient  //开启发现服务功能
@SpringBootApplication
public class SpringBoot14SpringcloudConsumerApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringBoot14SpringcloudConsumerApplication.class, args);
    }

    @LoadBalanced  //使用负载均衡机制
    @Bean          // RestTemplate 发送 Http 请求
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

　　4、使用提供者的服务，使用 RestTemplate 来调用

@RestController
public class UserController {


    @Autowired
    RestTemplate restTemplate;

    @GetMapping(value = "/buy")
    public String buyTicket(String name) {
        String s = restTemplate.getForObject("http://provider-ticket/ticket", String.class);
        return name + "购买了" + s;
    }
}

　　5、测试

　　服务提供者与使用者都注册在注册中心里

　　

　　发送请求：

　　　　

　　使用了负载均衡机制：