spring cloud ribbon with eureka

introduction

在上一篇中阐述了ribbon的基本用法，但是可以发现服务列表是通过配置得来的，实际 情况通常是由负载均衡+服务发现来实现的，通过服务发现获取服务列表，负载均衡通过rule选择要调用的服务。服务发现可以通过eureka来实现，后期会讲解利用consul做服务发现。

eureka discovery service

eureka服务发现在前面的文章中已经提供到，这里直接给出代码

首先是 eureka server

package com.lkl.springcloud.ribbon;

import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
import org.springframework.context.annotation.Configuration;

@Configuration
@EnableAutoConfiguration
@EnableEurekaServer
public class EurekaServerApplication {

    public static void main(String[] args) {
        new SpringApplicationBuilder(EurekaServerApplication.class).properties(
                "spring.config.name:eureka", "logging.level.com.netflix.discovery:OFF")
                .run(args);
    }

}

对应配置文件：

server.port=8761
spring.application.name= eureka
eureka.client.registerWithEureka=false
eureka.client.fetchRegistry=false

在eureka上进行服务注册SimpleApplication.java

package com.lkl.springcloud.ribbon;

import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@Configuration
@EnableAutoConfiguration
@EnableDiscoveryClient
@RestController
public class SimpleApplication {

    @RequestMapping("/")
    public String hello() {
        return "Hello";
    }

    public static void main(String[] args) {
        new SpringApplicationBuilder(SimpleApplication.class).properties(
                "spring.config.name:simple").run(args);
    }    
}

对应client配置

server.port= 8081
spring.application.name= simple
eureka.instance.leaseRenewalIntervalInSeconds= 10
eureka.client.registryFetchIntervalSeconds= 5
eureka.client.serviceUrl.defaultZone= http://localhost:${eureka.port:8761}/eureka/

ribbon + eureka

Application.java

package com.lkl.springcloud.ribbon;

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.context.annotation.Bean;
import org.springframework.http.client.SimpleClientHttpRequestFactory;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

/**
 * Created by liaokailin on 16/5/9.
 */
@SpringBootApplication
@EnableDiscoveryClient
@RestController
public class Application {

    @Autowired
    RestTemplate client;

    /**
     * LoadBalanced 注解表明restTemplate使用LoadBalancerClient执行请求
     *
     * @return
     */
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        RestTemplate template = new RestTemplate();
        SimpleClientHttpRequestFactory factory = (SimpleClientHttpRequestFactory) template.getRequestFactory();
        factory.setConnectTimeout(3000);
        factory.setReadTimeout(3000);
        return template;
    }

    @RequestMapping("/")
    public String helloWorld() {
        return client.getForObject("http://simple/", String.class);
    }


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


}

EnableDiscoveryClient 表明为eureka client 通过可以进行服务发现

RestTemplate 构建RestTemplate对应的bean，在method上使用注解LoadBalanced表示restTemplate使用LoadBalancerClient执行请求

对应配置文件

spring.application.name=RibbionClient
eureka.instance.leaseRenewalIntervalInSeconds= 10
eureka.client.registryFetchIntervalSeconds= 5
eureka.client.serviceUrl.defaultZone= http://localhost:${eureka.port:8761}/eureka/

run Application.java后访问http://localhost:8080/调用`helloWorld()`方法，该方法访问`http://simple/` 其中的simple为SimpleApplication.java 在eureka上注册的service id，即实际调用

@RequestMapping("/")
    public String hello() {
        return "Hello";
    }

因此得到返回结果Hello.