SpringCloud distributed micro-cloud infrastructure services The second: the service consumer rest + ribbon (Finchley

In the last article, about the service registration and discovery. In the micro-service architecture, the business will be split into a separate service, communication services and services based on the http restful. Spring cloud service calls in two ways, one is a ribbon + restTemplate, the other is feign. In this article first explains the basis ribbon + rest.

A, ribbon Profile

IS A Client Side Load the Ribbon Balancer Which Gives you A Lot of Control
over The Behavior of the HTTP and the TCP Clients. Feign already uses the Ribbon,
SO IF you are the using the then the this @FeignClient sectionTop Also Applies.
----- taken from the official website
ribbon is a client load balancing, can be well controlled some of the behavior of htt and tcp. Feign default integrated ribbon.

ribbon has achieved these default configuration bean:
ribbon is a client load balancing, you can be well controlled some of the behavior of htt and tcp. Feign default integrated ribbon.

ribbon has achieved these default configuration bean:

• IClientConfig ribbonClientConfig: DefaultClientConfigImpl
• IRule ribbonRule: ZoneAvoidanceRule
• IPing ribbonPing: NoOpPing
• ServerList ribbonServerList: ConfigurationBasedServerList
• ServerListFilter ribbonServerListFilter: ZonePreferenceServerListFilter

• ILoadBalancer ribbonLoadBalancer: ZoneAwareLoadBalancer
  Second, the preparation of
  this article based on an article of the project, starting eureka-server project; project start service-hi, the port is 8762; the port service-hi's profile is changed to 8763 and start to understand springcloud architecture can be added to beg: 3536247259, then you will find: service-hi registered two instances eureka-server, which is equivalent to a small cluster .
  
  Third, build a service consumer
  to re-create a spring-boot project, named: service-ribbon;
  it's pom.xml inherits the parent pom file, and introduces the following dependence:

  
  <?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.forezp</groupId>
  <artifactId>service-ribbon</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>
  
  <name>service-ribbon</name>
  <description>Demo project for Spring Boot</description>
  
  <parent>
      <groupId>com.forezp</groupId>
      <artifactId>sc-f-chapter2</artifactId>
      <version>0.0.1-SNAPSHOT</version>
  </parent>
  
  <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.cloud</groupId>
          <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
      </dependency>
  </dependencies>

</project>

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

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。

@SpringBootApplicationbr/>@EnableEurekaClient
@EnableDiscoveryClient
public class ServiceRibbonApplication {

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

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

}

写一个测试类HelloService，通过之前注入ioc容器的restTemplate来消费service-hi服务的“/hi”接口，在这里我们直接用的程序名替代了具体的url地址，在ribbon中它会根据服务名来选择具体的服务实例，根据服务实例在请求的时候会用具体的url替换掉服务名，代码如下：

@Service
public class HelloService {

@Autowired
RestTemplate restTemplate;

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

}

写一个controller，在controller中用调用HelloService 的方法，代码如下：

@RestController
public class HelloControler {

@Autowired
HelloService helloService;

@GetMapping(value = "/hi")
public String hi(@RequestParam String name) {
    return helloService.hiService( name );
}

}

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。

四、此时的架构

![](https://s1.51cto.com/images/blog/201912/12/d45cc4c70776a03f99f0daec76cd9ead.png?x-oss-process=image/watermark,size_16,text_QDUxQ1RP5Y2a5a6i,color_FFFFFF,t_100,g_se,x_10,y_10,shadow_90,type_ZmFuZ3poZW5naGVpdGk=)
* 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．