eureka注册中心上的服务消费者访问服务提供者（重要！！！！！）

原理：

其中涉及到3中角色：

服务注册中心：作为eureka的一个server，提供服务注册和发现的功能。在启动类中加注解@EnableEurekaServer

服务提供者：作为eureka的一个客户端组件，可以对外提供服务。在启动类中加注解@EnableEurekaClient

服务消费者：作为eureka的一个客户端组件，用来消费服务。在启动类中加注解@EnableEurekaClient

过程：

1.服务注册中心eureka server先启动

2.eureka client的服务提供者向服务注册中心eureka server进行注册。

3.eureka client的服务消费者向服务注册中心eureka server注册，同时从注册中心获取一份服务注册列表的信息，该列表包含了所有向服务注册中心eureka server注册的服务信息。获取服务注册列表信息之后，服务消费者就知道服务提供者的IP地址，可以通过HTTP远程调度来访问提供者提供的服务。

4.服务消费者和服务提供者对于服务注册中心来讲，都是客户端。

consumer:

controller:

package com.ljf.weifuwu.springcloud.eureka.consumer.controller;

import com.ljf.weifuwu.springcloud.eureka.consumer.model.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
public class ConsumerUserController
{   @Autowired
private RestTemplate restTemplate;
    @GetMapping("/consumer-eureka/{id}")
    public User findById(@PathVariable Long id) {
       return this.restTemplate.getForObject("http://localhost:7900/eureka-provider/" + id, User.class);
        //为何不能用下面这种方式？？？？？？？？？？
        //return this.restTemplate.getForObject("http://ms-eureka-provider/eureka-provider/" + id, User.class);
    }
}
           

启动类：

package com.ljf.weifuwu.springcloud.eureka.consumer;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

/**
 * Hello world!
 *
 */
@SpringBootApplication
@EnableEurekaClient
public class ConsumerEurekaApp
{   @Bean
public RestTemplate restTemplate() {
    return new RestTemplate();
}
    public static void main( String[] args )
    {
        SpringApplication.run(ConsumerEurekaApp.class, args);
        System.out.println( "eureka-consumer启动起来了！！！" );
    }
}
           

provider：

controller：

package com.ljf.weifuwu.springcloud.eureka.provider.controller;

import com.ljf.weifuwu.springcloud.eureka.provider.model.EurekaUser;

import com.ljf.weifuwu.springcloud.eureka.provider.respository.EurekaUserRespository;
import com.netflix.appinfo.InstanceInfo;
import com.netflix.discovery.EurekaClient;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {
    @Autowired
    @Qualifier("eurekaClient")
    private EurekaClient eurekaClient;
    @Autowired
    private DiscoveryClient discoveryClient;
    @Autowired
    private EurekaUserRespository userRepository;
    @GetMapping("/eureka-instance")
    public String serviceUrl() {
        //和配置文件配置的application.name=ms-eureka-provider保持一致
        //获取配置文件的ip和端口号：http://localhost:7900/eureka-instance
        InstanceInfo instance = this.eurekaClient.getNextServerFromEureka("ms-eureka-provider", false);
        return instance.getHomePageUrl();
    }
    @GetMapping("/instance-info")
    public ServiceInstance showInfo() {
        //http://localhost:7900/instance-info
        //"host":"192.168.1.225","port":7900,"serviceId":"ms-eureka-provider","metadata":{},"secure":false,"uri":"http://192.168.1.225:7900"}
        ServiceInstance localServiceInstance = this.discoveryClient.getLocalServiceInstance();
        return localServiceInstance;
    }
    @GetMapping("/eureka-provider/{id}")
    public EurekaUser getSingleUser(@PathVariable Long id){
        return this.userRepository.findOne(id);

    }
}
           

respository：

package com.ljf.weifuwu.springcloud.eureka.provider.respository;

import com.ljf.weifuwu.springcloud.eureka.provider.model.EurekaUser;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
@Repository
public interface EurekaUserRespository extends JpaRepository<EurekaUser, Long> {
    }

data.sql:
           

insert into eurekauser(id,username, name, age, balance) values(1,'user1', 'liu', 20, 100.00);
insert into eurekauser(id,username, name, age, balance) values(2,'user2', 'jian', 20, 100.00);
insert into eurekauser(id,username, name, age, balance) values(3,'user3', 'fu', 20, 100.00);
insert into eurekauser(id,username, name, age, balance) values(4,'user4', 'jurf', 20, 100.00);
           

schema.sql:

drop table eurekauser if exists;
create table eurekauser(
   id bigint generated by default as identity,
   username varchar(40),
   name varchar(20),
   age int(3),
   balance decimal(10,2), 
   primary key(id)
);
           

启动类：

package com.ljf.weifuwu.springcloud.eureka.provider;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

/**
 * Hello world!
 *
 */
@SpringBootApplication
@EnableEurekaClient
public class EurekaProviderApp
{
    public static void main( String[] args )
    {
        SpringApplication.run(EurekaProviderApp.class,args);
        System.out.println( "eurka中的提供者启动成功!" );
    }
}
           

页面访问：http://localhost:7901/consumer-eureka/1