springcloud（四）服务消费者（rest+ribbon）负载均衡

1.准备工作（设置idea开启多个springboot实例）

https://blog.csdn.net/qq_42014192/article/details/89245306

2.新建一个spring-boot工程，取名为：service-ribbon;

https://blog.csdn.net/qq_42014192/article/details/88742559

3.pom.xml依赖

<?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>2.1.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>springcloud_service-ribbon_demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springcloud_service-ribbon_demo</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Greenwich.SR1</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.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</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>

4.配置文件application.yml如下：

server:
  port: 8764 #服务端口

spring:
  application:
    name: service-ribbon

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

5.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。

@SpringBootApplication
//通过注解@EnableEurekaClient 表明自己是一个eurekaclient
@EnableEurekaClient
//通过@EnableDiscoveryClient向服务中心注册
@EnableDiscoveryClient
public class SpringcloudServiceRibbonDemoApplication {

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

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

}

6.写一个测试类HelloService

@Service
public class HelloService {
    @Autowired
    RestTemplate restTemplate;

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

7.写一个controller

@RestController
public class HelloController {

    @Autowired
    private HelloService helloService;

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

8.在浏览器上多次访问http://localhost:8764/client?name=forezp，浏览器交替显示：

client forezp,i am from port:8762
client forezp,i am from port:8763

9.架构

一个服务注册中心，Eureka-server,端口为8761

service-client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-client的client接口时，因为用ribbon进行了负载均衡，会轮流的调用service-client：8762和8763 两个端口的client接口；

注意：5步骤如何少been就不会出现下错误，解决办法将RestTemplate添加到spring容器中

***************************
APPLICATION FAILED TO START
***************************
Description:
Field restTemplate in com.example.springcloud_serviceribbon_demo.service.HelloService required a bean of type 'org.springframework.web.client.RestTemplate' that could not be found.

The injection point has the following annotations:
	- @org.springframework.beans.factory.annotation.Autowired(required=true)
Action:
Consider defining a bean of type 'org.springframework.web.client.RestTemplate' in your configuration.

springcloud（四）服务消费者（rest+ribbon）负载均衡

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