Ribbon (three)

Summary:

1. Load balancing framework that supports pluggable load balancing rules
2. Support for multiple protocols, such as Http, UDP, etc.
3. Provide load balancing client (the caller using the service client)

Ribbon sub-module

ribbon-core

    Including load balancing, and load balancing rules in this package

ribbon-eureka

    Load balancing class provided to clients erurka 

ribbon-httpclient

    rest contain client load balancing feature

Load Balancer components

1, a load balancer, at least the following functions

    To maintain the server ip and other information

   According to a particular logical server selection

2, in order to achieve the basic load balancing, load balancing the Ribbon has three sub-module

   Rule: Rule

   Ping

   ServerList

Analog @LoadBalanced principle

@LoadBalanced annotations to achieve load balancing by interceptor

1, a new comment

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, register RestTemplate instances into the container, and add custom annotations

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, custom interceptors, load balancing logic can be written, 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, the class definition configuration, automatic assembly RestTemplate to tpls, and add custom interceptor to RestTemplate interceptor

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、