# 服务消费者(rest+ribbon)

## 建立一个ribbon消费者

### 准备工作

这一篇文章基于上一篇文章的工程，启动eureka-server 工程；启动service-hi工程，它的端口为8762；将service-hi的配置文件的端口改为8763,并启动，这时你会发现：service-hi在eureka-server注册了2个实例，这就相当于一个小的集群。访问localhost:8761如图所示：

![](/files/-Lys2rBADhth_a1szVkJ)

### 创建一个工程为service-ribbon

重新新建一个spring-boot工程，取名为：service-ribbon;

在它的pom.xml文件分别引入起步依赖spring-cloud-starter-eureka、spring-cloud-starter-ribbon、spring-boot-starter-web，代码如下：

```markup
<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.itmayiedu</groupId>
	<artifactId>springcloud-2.0-order</artifactId>
	<version>0.0.1-SNAPSHOT</version>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.0.1.RELEASE</version>
	</parent>
	<!-- 管理依赖 -->
	<dependencyManagement>
		<dependencies>
			<dependency>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-dependencies</artifactId>
				<version>Finchley.M7</version>
				<type>pom</type>
				<scope>import</scope>
			</dependency>
		</dependencies>
	</dependencyManagement>
	<dependencies>
		<!-- SpringBoot整合Web组件 -->
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<!-- SpringBoot整合eureka客户端 -->
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
		</dependency>
		<!-- SpringCloud整合ribbon客户端 -->
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
		</dependency>

	</dependencies>
	<!-- 注意： 这里必须要添加， 否者各种依赖有问题 -->
	<repositories>
		<repository>
			<id>spring-milestones</id>
			<name>Spring Milestones</name>
			<url>https://repo.spring.io/libs-milestone</url>
			<snapshots>
				<enabled>false</enabled>
			</snapshots>
		</repository>
	</repositories>
</project>
```

## application.yml配置

在工程的配置文件指定服务的注册中心地址为<http://localhost:8761/eureka/，程序名称为> service-ribbon，程序端口为8764。配置文件application.yml如下：

```
eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
server:
  port: 8764
spring:
  application:
    name: service-ribbon
```

## 启动类@EnableDiscoveryClient

在工程的启动类中,通过@EnableDiscoveryClient向服务中心注册；并且向程序的ioc注入一个bean: restTemplate;并通过@LoadBalanced注解表明这个restRemplate开启负载均衡的功能。

```java
@SpringBootApplication
@EnableDiscoveryClient
public class ServiceRibbonApplication {

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

	@Bean
	@LoadBalanced
	RestTemplate restTemplate() {
		return new RestTemplate();
	}

}
```

## 编写一个service

```java
@Service
public class HelloService {

    @Autowired
    RestTemplate restTemplate;

    public String hiService(String name) {
        return restTemplate.getForObject("http://SERVICE-HI/hi?name="+name,String.class);
    }

}
```

## 编写一个控制器层

```java
@RestController
public class HelloControler {
    @Autowired
    HelloService helloService;
    @RequestMapping(value = "/hi")
    public String hi(@RequestParam String name){
        return helloService.hiService(name);
    }
}
```

## 演示效果

在浏览器上多次访问<http://localhost:8764/hi?name=forezp，浏览器交替显示：>

hi forezp,i am from port:8762

hi forezp,i am from port:8763

这说明当我们通过调用restTemplate.getForObject(“<http://SERVICE-HI/hi?name=“+name,String.class)方法时，已经做了负载均衡，访问了不同的端口的服务实例。>

## 此时架构

![](/files/-Lys2ymzAShYB5YNcZ6x)

* 一个服务注册中心，eureka server,端口为8761
* service-hi工程跑了两个实例，端口分别为8762,8763，分别向服务注册中心注册
* sercvice-ribbon端口为8764,向服务注册中心注册
* 当sercvice-ribbon通过restTemplate调用service-hi的hi接口时，因为用ribbon进行了负载均衡，会轮流的调用service-hi：8762和8763 两个端口的hi接口；
* @LoadBalanced注解表明这个restRemplate开启负载均衡的功能。

## 资料

[SpringCloud笔记（三）使用DiscoveryClient手动实现客户端负载均衡](https://blog.csdn.net/zhoujian_Liu/article/details/85201967)


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