SpringCloud (Finchley Version) Tutorial (2): Service Consumers (REST + RIBBON)

By System Architecture

In the previous article, I talked about service registration and discovery. In the microservice architecture, the business will be split into an independent service, and the communication between the service and the service is based on http restful. Spring cloud has two service invocation methods, one is ribbon+restTemplate, and the other is feign. In this article, first explain the ribbon+rest based.

I. Introduction to ribbon

Ribbon is a load balancing client, which can well control some behaviors of htt and tcp. Feign integrates ribbon by default.

ribbon has implemented these configuration beans by default:

IClientConfig ribbonClientConfig: DefaultClientConfigImpl

IRule ribbonRule: ZoneAvoidanceRule

IPing ribbonPing: NoOpPing< /p>

ServerList ribbonServerList: ConfigurationBasedServerList

ServerListFilter ribbonServerListFilter: ZonePreferenceServerListFilter

ILoadBalancer ribbonLoadBalancer: ZoneAwareLoadBalancer

Second, preparations
this article Based on the project in the previous article, start the eureka-server project; start the service-hi project, its port is 8762; change the port of the service-hi configuration file to 8763, and start it, then you will find: service- hi has registered 2 instances on eureka-server, which is equivalent to a small cluster.

Visit localhost:8761 as shown in the figure: there are two clients.

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3. Build a service consumer
Create a new spring-boot project and name it: service-ribbon;
in its pom .xml inherits the parent pom file and introduces the following dependencies:





 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

 4.0.0

 

 com.liu

 SpringCloudLearn01

 1.0-SNAPSHOT

 



 com.liu.example

 service-ribbon

 0.0.1-SNAPSHOT

 service-ribbon

 Demo project for Spring Boot



 

 1.8

 



 

 

 org.springframework.cloud

 spring-cloud-starter-netflix-eureka-client

 



 

 org.springframework.cloud

 spring-cloud-starter-netflix-ribbon

 



 

 org.springframework.boot

 spring-boot-starter-web

 



 

 org.springframework.boot

 spring-boot-starter-test

 test

 



 



 

 

 

 org.springframework.boot

 spring-boot-maven-plugin

In the configuration file of the project, specify the service registration center address as http://localhost:8761/eureka/, the program name is service-ribbon, and the program The port is 8764. The configuration file application.yml is as follows:

server:

 port: 8764



spring:

 application:

 name: service-ribbon



eureka:

 client:

 service-url:

 defaultZone: http://localhost:8761/eureka/

In the startup class of the project, register with the service center through @EnableDiscoveryClient; and inject a bean: restTemplate into the program’s ioc; and use the @LoadBalanced annotation to indicate that this restRemplate opens load balancing Function. 

package com.liu.example. serviceribbon;



import org.springframework.beans.factory.annotation.Autowired;

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.cloud.netflix.eureka.EnableEurekaClient;

import org.springframework.cloud.netflix.hystrix.EnableHystrix;

import org.springframework.context.annotation.Bean;

import org.springframework.web.client.RestTemplate;



@SpringBootApplication

@EnableEurekaClient

@EnableDiscoveryClient

public class ServiceRibbonApplication {



 public static void main(String[] args) {

 SpringApplication.run(ServiceRibbonApplication.class, args);

}



 @Bean

 @LoadBalanced

 RestTemplate restTemplate(){

 return new RestTemplate();

}



}

Write a test class HelloService, and consume the “/hi” interface of the service-hi service through the restTemplate injected into the ioc container. Here we directly The program name is used instead of the specific URL address. In ribbon, it will select the specific service instance according to the service name. According to the service instance, it will replace the service name with the specific URL when requesting. The code is as follows:

package com.liu.example.serviceribbon.service;



import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand ;

import com.netflix.ribbon.proxy.annotation.Hystrix;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Service;

import org.springframework.web.client.RestTemplate;



@Service

public class HelloService {



 @Autowired

 RestTemplate restTemplate;

public String hiService(String name) {

 return restTemplate.getForObject("http://service-client/hi", String.class);

 }

}

Write a controller, use the method of calling HelloService in the controller, the code is as follows:

package com.liu.example.serviceribbon.controller;



import com.liu.example.serviceribbon.service.HelloService;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RequestParam;

import org.springframework.web.bind.annotation.RestController;



@RestController

public class HelloController {



 @Autowired

 HelloService helloService;



 @GetMapping(value = "/hi")

 public String hi(@RequestParam String name) {

 return helloService.hiService( name );

}

}

Visit http://localhost:8764/hi?name=forezp multiple times on the browser, the browser alternately displays:

hello! My port number is: 8762

hello! My port number is: 8763

This shows that when we call restTemplate.getForObject(“http:// In the SERVICE-HI/hi?name=”+name,String.class) method, load balancing has been done and service instances of different ports have been accessed.

Four. Architecture at this time

A service registry, eureka server, port 8761
The service-hi project ran two instances, the ports are 8762,8763 respectively , Respectively register with the service registry
sercvice-ribbon port is 8764, and register with the service registry
When sercvice-ribbon calls the hi interface of service-hi through restTemplate, because the ribbon is used for load balancing, it will take turns Call service-hi: hi interface of two ports 8762 and 8763;
Source code download: https://github.com/MrLiu1227/MySpringCloud.git

< ?xml version="1.0" encoding="UTF-8"?>



 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

 4.0.0

 

 com.liu

 SpringCloudLearn01

 1.0-SNAPSHOT

 



 com.liu.example

 service-ribbon

 0.0.1-SNAPSHOT

 service-ribbon

 Demo project for Spring Boot



 

 1.8

 



 

 

 org.springframework.cloud

 spring-cloud-starter-netflix-eureka-client

 



 

 org.springframework.cloud

 spring-cloud-starter-netflix-ribbon

 



 

 org.springframework.boot

 spring-boot-starter-web

 



 

 org.springframework.boot

 spring-boot-starter-test

 test

 



 



 

 

 

 org.springframework.boot

 spring-boot-maven-plugin

 

 

 




server:

 port: 8764



spring:

 application:

 name: service-ribbon



eureka:

 client:

 service-url:

 defaultZone: http://localhost:8761/eureka/

package com.liu.example .serviceribbon;



import org.springframework.beans.factory.annotation.Autowired;

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.cloud.netflix.eureka.EnableEurekaClient;

import org.springframework.cloud.netflix.hystrix.EnableHystrix;

import org.springframework.context.annotation.Bean;

import org.springframework.web.client.RestTemplate;



@SpringBootApplication

@EnableEurekaClient

@EnableDiscoveryClient

public class ServiceRibbonApplication {



 public static void main(String[] args) {

 SpringApplication.run(ServiceRibbonApplication.class, args);

}



 @Bean

 @LoadBalanced

 RestTemplate restTemplate(){

 return new RestTemplate();

}



}

package com.liu.example.serviceribbon.service;



import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand ;

import com.netflix.ribbon.proxy.annotation.Hystrix;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Service;

import org.springframework.web.client.RestTemplate;



@Service

public class HelloService {



 @Autowired

 RestTemplate restTemplate;

public String hiService(String name) {

 return restTemplate.getForObject("http://service-client/hi", String.class);

 }

}

package com.liu.example.serviceribbon.controller;



import com.liu.example.serviceribbon.service.HelloService;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RequestParam;

import org.springframework.web.bind.annotation.RestController;



@RestController

public class HelloController {



 @Autowired

 HelloService helloService;



 @GetMapping(value = "/hi")

 public String hi(@RequestParam String name) {

 return helloService.hiService( name );

}

}

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