详解spring cloud中使用Ribbon实现客户端的软负载均衡

package com.chhliu.springboot.restful; 
import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.boot.SpringApplication; 
import org.springframework.boot.autoconfigure.SpringBootApplication; 
import org.springframework.boot.web.client.RestTemplateBuilder; 
import org.springframework.cloud.client.loadbalancer.LoadBalanced; 
import org.springframework.cloud.netflix.eureka.EnableEurekaClient; 
import org.springframework.context.annotation.Bean; 
import org.springframework.web.client.RestTemplate; 
@SpringBootApplication 
@EnableEurekaClient 
public class SpringbootRestTemplateApplication { 
   
  @Autowired 
  private RestTemplateBuilder builder; 
 
  @Bean 
  @LoadBalanced // 添加负载均衡支持，很简单，只需要在RestTemplate上添加@LoadBalanced注解，那么RestTemplate即具有负载均衡的功能,如果不加@LoadBalanced注解的话，会报java.net.UnknownHostException:springboot-h2异常，此时无法通过注册到Eureka Server上的服务名来调用服务，因为RestTemplate是无法从服务名映射到ip:port的，映射的功能是由LoadBalancerClient来实现的。 
  public RestTemplate restTemplate() { 
    return builder.build(); 
  } 
 
  public static void main(String[] args) { 
    SpringApplication.run(SpringbootRestTemplateApplication.class, args); 
  } 
} 

package com.chhliu.springboot.restful.controller; 
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;  
import com.chhliu.springboot.restful.vo.User; 
 
@RestController 
public class RestTemplateController { 
  @Autowired 
  private RestTemplate restTemplate; 
   
  @GetMapping("/template/{id}") 
  public User findById(@PathVariable Long id) {// 将原来的ip:port的形式，改成注册到Eureka Server上的应用名即可 
    User u = this.restTemplate.getForObject("http://springboot-h2/user/" + id, User.class); 
    System.out.println(u); 
    return u; 
  } 
} 

Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 
Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 
Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 
Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 

Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 
Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 
Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 
Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 
Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 

User [id=2, username=user2, name=李四, age=20, balance=100.00] 
2017-01-23 09:58:05.682 INFO 7436 --- [erListUpdater-0] c.netflix.config.ChainedDynamicProperty : Flipping property: springboot-h2.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647 
User [id=2, username=user2, name=李四, age=20, balance=100.00] 
User [id=2, username=user2, name=李四, age=20, balance=100.00] 
User [id=2, username=user2, name=李四, age=20, balance=100.00] 
User [id=2, username=user2, name=李四, age=20, balance=100.00] 
User [id=2, username=user2, name=李四, age=20, balance=100.00] 
User [id=2, username=user2, name=李四, age=20, balance=100.00] 
User [id=2, username=user2, name=李四, age=20, balance=100.00] 
User [id=2, username=user2, name=李四, age=20, balance=100.00]