springcloud中Ribbon和RestTemplate实现服务调用与负载均衡

文件目录结构

文件目录结构很重要，特别注意的是rule文件要放在主启动类上一级位置，才能够扫描。

写pom

<dependencies>
       <!--springboot 2.2.2-->
       <dependency>
           <groupId>org.springframework.boot</groupId>
           <artifactId>spring-boot-starter-web</artifactId>
       </dependency>
       <!--Spring cloud Hoxton.SR1-->
       <dependency>
           <groupId>org.springframework.boot</groupId>
           <artifactId>spring-boot-starter-actuator</artifactId>
       </dependency>
       <!--Spring cloud alibaba 2.1.0.RELEASE-->
       <dependency>
           <groupId>org.projectlombok</groupId>
           <artifactId>lombok</artifactId>
           <optional>true</optional>
       </dependency>
       <dependency>
           <groupId>org.springframework.boot</groupId>
           <artifactId>spring-boot-starter-test</artifactId>
           <scope>test</scope>
       </dependency>
       <!--Eureka-Client-->
       <dependency>
           <groupId>org.springframework.cloud</groupId>
           <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
       </dependency>

因为eureka的依赖已经整合了ribbon的依赖，所以不用额外引入新的东西。

改yml

server:
 port: 80
spring:
 application:
   name: cloud-book-consumer
eureka:
 client:
   register-with-eureka: false
   fetch-registry: true
   service-url:
     defaultZone: http://eureka7001.com:7001/eureka,http://eureka7002.com:7002/eureka

主启动

@SpringBootApplication
@EnableEurekaClient
@RibbonClient(name = "CLOUD-BOOK-SERVICE", configuration = LoadBalanceRule.class)   //更换轮询算法
public class RestTemplateMain80 {
   public static void main(String[] args) {
       SpringApplication.run(RestTemplateMain80.class,args);
   }
}

业务逻辑

rules层

在图示文件目录下新建LoadBalanceRule.class，用于更换负载均衡算法。

@Configuration
public class LoadBalanceRule {
   @Bean
   public IRule iRule() {
       // 定义为随机
       return new RandomRule();
   }
}

config层

开启restTemplate负载均衡
在config文件夹下创建LoadBalanceConfig.class

@Configuration
public class LoadBalanceConfig {
   @Bean
   @LoadBalanced            //开启负载均衡
   public RestTemplate getReatTemplate(){
       return new RestTemplate();
   }
}

controller层

新建BookController.class
写业务代码

@RestController
@Slf4j
public class BookController {
   @Resource
   private RestTemplate restTemplate;

public static final String PAYMENT_URL = "http://CLOUD-BOOK-SERVICE";

@GetMapping(value = "restTemplate/book/getAllBooks")//只要json数据时
   public CommonResult getAllBooks(){
       return restTemplate.getForObject(PAYMENT_URL+"/book/getAllBooks",CommonResult.class);
   }

@GetMapping("restTemplate/book/getAllBooks2")    //需要知道更多数据时，使用getForEntity方法
   public CommonResult getAllBooks2(){
       ResponseEntity<CommonResult> resultResponseEntit = restTemplate.getForEntity(PAYMENT_URL+"/book/getAllBooks",CommonResult.class);
       if (resultResponseEntit.getStatusCode().is2xxSuccessful()){
           log.info(resultResponseEntit.getStatusCode()+"\t"+resultResponseEntit.getHeaders());
           return resultResponseEntit.getBody();
       }else {
           return new CommonResult<>(444,"操作失败");
       }
   }
   @GetMapping(value = "restTemplate/book/index")
   public String index() {
       return restTemplate.getForObject(PAYMENT_URL+"/book/index",String.class);
   }
}

使用restTemplate+Ribboin实现服务调用和负载均衡完成。

手写Ribbon负载均衡算法 lb层

1.新建LoadBalancer接口，添加代码

public interface LoadBalancer {
   ServiceInstance instances(List<ServiceInstance> serviceInstances);
}

2.新建实现类MyLB

@Component
public class MyLB implements LoadBalancer {

private AtomicInteger atomicInteger = new AtomicInteger(0);
   //求第几次访问  自旋锁思想
   public final int getAndIncrement(){
       int current;
       int next;
       do {
           current = this.atomicInteger.get();
           next = current >=2147483647 ? 0 : current+1;
       }while(!this.atomicInteger.compareAndSet(current,next));
       System.out.println("***第几次访问next->"+next);
       return next;
   }

//负载均衡算法,实现roundRobin算法
   @Override
   public ServiceInstance instances(List<ServiceInstance> serviceInstances) {

int index = getAndIncrement() ％ serviceInstances.size();

return serviceInstances.get(index);
   }
}

修改BookController

@RestController
@Slf4j
public class BookController {
   @Resource
   private RestTemplate restTemplate;

@Resource
   private LoadBalancer loadBalancer;

@Resource
   private DiscoveryClient discoveryClient;

public static final String PAYMENT_URL = "http://CLOUD-BOOK-SERVICE";

@GetMapping(value = "restTemplate/book/getAllBooks")//只要json数据时
   public CommonResult getAllBooks(){
       List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-BOOK-SERVICE");
       if (instances == null || instances.size() <= 0){
           return null;
       }
       ServiceInstance serviceInstance = loadBalancer.instances(instances);
       URI uri = serviceInstance.getUri();
       return restTemplate.getForObject(uri+"/book/getAllBooks",CommonResult.class);
   }

@GetMapping(value = "restTemplate/book/index")
   public String index() {
       List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-BOOK-SERVICE");
       if (instances == null || instances.size() <= 0){
           return null;
       }
       ServiceInstance serviceInstance = loadBalancer.instances(instances);
       URI uri = serviceInstance.getUri();
       return restTemplate.getForObject(uri+"/book/index",String.class);
   }
}

修改文件注解

• 删去主启动类的更换负载均衡算法注解

@RibbonClient(name = “CLOUD-BOOK-SERVICE”, configuration = LoadBalanceRule.class)

• 删去LoadBalanceConfig中开启负载均衡算法注解

@LoadBalanced

手写Ribbon算法并使用完成

来源：https://blog.csdn.net/super1223/article/details/115384982