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public class CustomLoadBalancerConfiguration {
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    /*
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          environment：包含了一些配置信息
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          loadBalancerClientFactory：创建LoadBalancerClient对象的工厂
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     */
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    @Bean
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    ReactorLoadBalancer<ServiceInstance> randomLoadBalancer(Environment environment, LoadBalancerClientFactory loadBalancerClientFactory) {
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        // 获取目标服务名称
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        String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
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        // 创建用于获取目标服务实例列表的工厂对象
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        ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSuppliers
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                = loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class);
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        // 创建随机负载均衡器
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        return new RandomLoadBalancer(serviceInstanceListSuppliers, name);
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    }
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}

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public class MyLoadBalancer implements ReactorServiceInstanceLoadBalancer {
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    // 服务名称
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    final String serviceId;
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    // 获取ServiceInstanceListSupplier对象的工厂
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    ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider;
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    public MyLoadBalancer(String serviceId, ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider) {
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        this.serviceId = serviceId;
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        this.serviceInstanceListSupplierProvider = serviceInstanceListSupplierProvider;
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    }
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    /*
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        我们需要实现该方法，实现自己的自定义负载均衡策略
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    */
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    @Override
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    public Mono<Response<ServiceInstance>> choose(Request request) {
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    }
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}

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public class MyLoadBalancer implements ReactorServiceInstanceLoadBalancer {
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    // 服务名称
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    final String serviceId;
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    // 获取ServiceInstanceListSupplier对象的工厂
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    ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider;
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    public MyLoadBalancer(String serviceId, ObjectProvider<ServiceInstanceListSupplier> serviceInstanceListSupplierProvider) {
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        this.serviceId = serviceId;
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        this.serviceInstanceListSupplierProvider = serviceInstanceListSupplierProvider;
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    }
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    @Override
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    public Mono<Response<ServiceInstance>> choose(Request request) {
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        // 得到获取服务实例列表的supplier对象
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        ServiceInstanceListSupplier serviceInstanceListSupplier = serviceInstanceListSupplierProvider.getIfAvailable(NoopServiceInstanceListSupplier::new);
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        //
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        return serviceInstanceListSupplier
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                // 获取目标服务实例列表
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                .get(request)
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                // 取出第一个列表(实际上)
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                .next()
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                // 将服务列表转化为一个服务实例(其实就是选择一个服务实例)
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                .map(serviceInstances -> doChooseSingleServer(serviceInstances));
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    }
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    /*
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         通过这个方法时实际完成服务实例的选择
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     */
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    private Response<ServiceInstance> doChooseSingleServer(List<ServiceInstance> serviceInstances) {
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        // 选择策略简单粗暴，选择列表中的第一个服务实例
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        ServiceInstance serviceInstance = serviceInstances.get(0);
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        // 将选择结果封装到DefaultResponse中返回
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        return new DefaultResponse(serviceInstance);
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    }
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}

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spring:
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  cloud:
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    gateway:
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     #定义多个路由
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      routes:
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      # 一个路由route的id
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      - id:  test_route
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        # 该路由转发的目标URI
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        uri: https://example.org
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        # 路由条件集合
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        predicates:
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        - Path=/red/**
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        # 过滤器集合
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        filters:
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        - AddRequestParameter=color, red

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<dependencies>
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        <!--gateway-->
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        <dependency>
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            <groupId>org.springframework.cloud</groupId>
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            <artifactId>spring-cloud-starter-gateway</artifactId>
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        <!--loadbalancer依赖-->
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        </dependency>
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                <dependency>
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            <groupId>org.springframework.cloud</groupId>
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            <artifactId>spring-cloud-loadbalancer</artifactId>
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        </dependency>
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        <!--单元测试依赖-->
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        <dependency>
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            <groupId>org.springframework.boot</groupId>
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            <artifactId>spring-boot-starter-test</artifactId>
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        </dependency>
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    </dependencies>

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spring:
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  application:
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    name: cloud-gateway
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  cloud:
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    nacos:
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      discovery:
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        server-addr: localhost:8848
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    gateway:
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      routes:
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         #路由的ID，没有固定规则但要求唯一，建议配合服务名
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        - id: config_route
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          #匹配后提供服务的路由地址, 这里lb之后，跟的是要调用的服务名称
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          uri: lb://nacos-provider-8002
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           # 断言，路径相匹配的条件
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          predicates:
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            - Path=/routeconfig/rest/**

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@Component
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public class MyGatewayFilter implements GlobalFilter, Ordered {
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    @Override
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    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
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        ServerHttpRequest request = exchange.getRequest();
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        MultiValueMap<String, HttpCookie> cookies = request.getCookies();
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        List<HttpCookie> tokens = cookies.get("access_token");
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        if (tokens == null || tokens.size() == 0) {
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            throw new RuntimeException("少了cookie！");
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        }
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        return chain.filter(exchange);
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    }
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    @Override
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    public int getOrder() {
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       return 0;
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    }
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}