Ribbon(三)

简介：

1. 负载均衡框架，支持可插拔式的负载均衡规则
2. 支持多种协议，如Http,UDP等
3. 提供负载均衡的客户端(用在服务调用者client)

Ribbon子模块

ribbon-core

    包括负载均衡，以及负载均衡规则都在这个包里

ribbon-eureka

    为erurka客户端提供的负载均衡类 

ribbon-httpclient

    含有负载均衡功能的rest客户端

负载均衡器组件

1、一个负载均衡器，至少提供以下功能

    要维护各个服务器的ip等信息

   根据特定逻辑选取服务器

2、为了实现基本的负载均衡功能，Ribbon的负载均衡器有三大子模块

   Rule：规则

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   Ping

   ServerList

模拟@LoadBalanced原理

@LoadBalanced注解通过拦截器来实现负载均衡

1、新建一个注解

package spring.cloud.spring_member.controller.locdbalaned;

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

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * 自定义负载均衡的注解
 *
 * @param
 * @return
 * @date 2019-06-16 13:57
 */
@Target({ElementType.FIELD,ElementType.PARAMETER,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Qualifier
public @interface MyLoadBalanced {


}

2、注册RestTemplate实例到容器中，并加上自定义的注解

package spring.cloud.spring_member.controller.locdbalaned;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import java.awt.*;

/**
 * 类的描述 TODO
 *
 * @author wangwei
 * @Date 2019-06-16 14:04
 */
@RestController
@Configuration
public class MyController {

    @Bean
    @MyLoadBalanced
    RestTemplate tplA() {
        return new RestTemplate();
    }

    @Bean
    @MyLoadBalanced
    RestTemplate tplB() {
        return new RestTemplate();
    }

    @RequestMapping(value = "/call", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
    public String call() {

        RestTemplate tpl = tplA();
        //被拦截器拦截，拦截器内部实现负载均衡
        String json = tpl.getForObject("http://app-member-server/call", String.class);
        return json;
    }

}

3、自定义拦截器，可以可以写负载均衡逻辑，todo

package spring.cloud.spring_member.controller.locdbalaned;

import org.springframework.http.HttpRequest;
import org.springframework.http.client.ClientHttpRequestExecution;
import org.springframework.http.client.ClientHttpRequestInterceptor;
import org.springframework.http.client.ClientHttpResponse;

import java.io.IOException;

/**
 * 自定义拦截器
 *
 * @author wangwei
 * @Date 2019-06-16 14:08
 */
public class MyInterceptor implements ClientHttpRequestInterceptor {

    @Override
    public ClientHttpResponse intercept(HttpRequest httpRequest, byte[] bytes, ClientHttpRequestExecution clientHttpRequestExecution) throws IOException {
        System.out.println("=========自定义拦截器");
        System.out.println("=========" + httpRequest.getURI());
        //可以在这里写负载均衡逻辑代码
        return null;
    }
}

4、定义配置类，给tpls自动装配restTemplate，并且给restTemplate的拦截器增加自定义的拦截器

package spring.cloud.spring_member.controller.locdbalaned;

import org.springframework.beans.factory.SmartInitializingSingleton;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.ClientHttpRequestInterceptor;
import org.springframework.web.client.RestTemplate;

import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;

/**
 * 定义配置类，给restTemplate的拦截器增加自定义的拦截器
 * @Date 2019-06-16 14:01
 */
@Configuration
public class MyConfig {

    @Autowired(required = false)
    @MyLoadBalanced
    private List<RestTemplate> tpls = Collections.emptyList();

    @Bean
    public SmartInitializingSingleton Ibinitalizing() {
        return new SmartInitializingSingleton() {
            @Override
            public void afterSingletonsInstantiated() {
                System.out.println(tpls.size());
                for(RestTemplate restTemplate : tpls){
                    List<ClientHttpRequestInterceptor> interceptors = restTemplate.getInterceptors();
                    interceptors.add(new MyInterceptor());
                    restTemplate.setInterceptors(interceptors);
                }
            }
        };
    }
}

4、