4 SpringCloud中服务消费者Ribbon

上面的Eurefa高可用依葫芦画瓢就弄，不是太明白怎么回事。但是有一点但是怎么去用呢，也就是怎么用负载均衡去调用。

注册中心server
添加依赖

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.9.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>

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

<dependencies>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-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>Dalston.RC1</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>

<repositories>
    <repository>
        <id>spring-milestones</id>
        <name>Spring Milestones</name>
        <url>https://repo.spring.io/milestone</url>
        <snapshots>
            <enabled>false</enabled>
        </snapshots>
    </repository>
</repositories>

配置文件

server:
  port: 8761

eureka:
  instance:
    hostname: localhost
  client:
    registerWithEureka: false
    fetchRegistry: false
    serviceUrl:
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/

上面的eureka.client.registerWithEureka= false表示为注册中心，自己不向自己注册
而eureka.client.fetchRegistry: false表示注册中心的职责就是维护服务实例，并不需要去检索服务。

启动类

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

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

完成了注册中心server。
服务提供者client
依赖在service的pom文件中将

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

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

替换 替换 替换 替换 替换 替换

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

配置文件

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
server:
  port: 8762
spring:
  application:
    name: service-hi

启动类

import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@EnableEurekaClient
@RestController
public class AppClient2 {

    public static void main(String[] args) {
        SpringApplication.run(AppClient2.class, args);
    }

    @Value("${server.port}")
    String port;
    @RequestMapping("/hi")
    public String home(@RequestParam String name) {
        return "hi "+name+",i am from port:" +port;
    }

}

client2和client一模一样，就是配置文件中server.port=8763

然后依次启动server，client，client2。
访问 http://localhost:8761/ 进入eurefa控制台，看到两个服务

Ribbon
依赖jar包在client的pom文件基础上加上

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

然后配置文件

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

Controller

@RestController
public class HelloControler {
    @Autowired
    HelloService helloService;

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

server

@Service
public class HelloService {

    @Autowired
    RestTemplate restTemplate;

    public String hiService(String name) {
        //通过启动类注入ioc容器的restTemplate来消费service-hi服务的“/hi”接口
        //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
        return restTemplate.getForObject("http://SERVICE-HI/hi?name="+name,String.class);
    }
}

启动类

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableDiscoveryClient
public class AppRibbon {

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

    //启动时自动注入ioc
    @Bean
    @LoadBalanced
    RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

然后启动这个ribbon。在eruefa控制台也会多一个服务。

然后不断刷新 http://localhost:8764/hi?name=lijia 来查看负载均衡
在浏览器中 出现两个不同的端口号8762和8763，这里面负载均衡已经完成。
此时的架构图

• 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；

代码放在 https://github.com/lijiaccy/springcloud-study/tree/master/eurefa-Ribbon 上

参考：http://blog.csdn.net/forezp/article/details/70148833