Spring Cloud 框架

约 686 字大约 2 分钟

2026-04-29

一、Spring Cloud 简介

Spring Cloud 是基于 Spring Boot 的微服务开发工具集，提供了一整套分布式系统解决方案。

1.1 版本关系

Spring Cloud	Spring Boot	说明
2023.x（Leyton）	3.2.x	当前最新稳定版
2022.x（Kilburn）	3.0.x / 3.1.x	上一代
2021.x（Jubilee）	2.7.x	维护中

1.2 核心组件

Spring Cloud
├── 注册中心：Eureka / Nacos / Consul
├── 配置中心：Spring Cloud Config / Nacos Config
├── 网关：Spring Cloud Gateway / Zuul
├── 负载均衡：Spring Cloud LoadBalancer
├── 远程调用：OpenFeign
├── 熔断降级：Resilience4j / Sentinel
├── 链路追踪：Sleuth + Zipkin / Micrometer Tracing
└── 消息驱动：Spring Cloud Stream

二、服务注册与发现

2.1 Eureka（Netflix）

// 服务端启动类
@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {
    public static void main(String[] args) {
        SpringApplication.run(EurekaServerApplication.class, args);
    }
}

# eureka-server application.yml
server:
  port: 8761
eureka:
  client:
    register-with-eureka: false   # 不注册自己
    fetch-registry: false

# 客户端 application.yml
spring:
  application:
    name: user-service
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/
  instance:
    prefer-ip-address: true

2.2 Nacos（Alibaba，推荐）

spring:
  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848
        namespace: dev

2.3 对比

	Eureka	Nacos	Consul
CAP	AP	AP/CP	CP
配置中心	不支持	支持	支持
健康检查	客户端心跳	TCP/HTTP/MySQL	TCP/HTTP/gRPC
社区维护	停更（2.x）	活跃	活跃

三、负载均衡

3.1 Spring Cloud LoadBalancer

@Configuration
public class RestTemplateConfig {
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

// 使用（通过服务名调用）
User user = restTemplate.getForObject(
    "http://user-service/api/users/" + id, User.class);

3.2 负载均衡策略

@Bean
public ReactorLoadBalancer<ServiceInstance> randomLoadBalancer(
        Environment environment,
        LoadBalancerClientFactory factory) {
    String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
    return new RandomLoadBalancer(
        factory.getLazyProvider(name, ServiceInstanceListSupplier.class), name);
}

策略	说明
RoundRobin（默认）	轮询
Random	随机
WeightedResponseTime	响应时间加权

四、声明式调用 — OpenFeign

@FeignClient(name = "order-service",
             fallbackFactory = OrderClientFallback.class)
public interface OrderClient {

    @GetMapping("/api/orders/user/{userId}")
    List<Order> getOrdersByUser(@PathVariable("userId") Long userId);

    @PostMapping("/api/orders")
    Order createOrder(@RequestBody Order order);
}

@Component
public class OrderClientFallback implements FallbackFactory<OrderClient> {
    @Override
    public OrderClient create(Throwable cause) {
        return new OrderClient() {
            public List<Order> getOrdersByUser(Long userId) {
                return Collections.emptyList();
            }
            public Order createOrder(Order order) {
                throw new RuntimeException("服务降级：" + cause.getMessage());
            }
        };
    }
}

五、API 网关 — Spring Cloud Gateway

5.1 路由配置

spring:
  cloud:
    gateway:
      routes:
        - id: user-service
          uri: lb://user-service
          predicates:
            - Path=/api/users/**
          filters:
            - StripPrefix=0

        - id: order-service
          uri: lb://order-service
          predicates:
            - Path=/api/orders/**
            - Method=GET,POST

5.2 全局过滤器

@Component
public class AuthFilter implements GlobalFilter, Ordered {
    @Override
    public Mono<Void> filter(ServerWebExchange exchange,
                             GatewayFilterChain chain) {
        String token = exchange.getRequest().getHeaders()
                          .getFirst("Authorization");
        if (!StringUtils.hasText(token)) {
            exchange.getResponse().setStatusCode(HttpStatus.UNAUTHORIZED);
            return exchange.getResponse().setComplete();
        }
        return chain.filter(exchange);
    }

    @Override
    public int getOrder() { return 0; }
}

5.3 限流

spring:
  cloud:
    gateway:
      routes:
        - id: user-service
          uri: lb://user-service
          predicates:
            - Path=/api/users/**
          filters:
            - name: RequestRateLimiter
              args:
                redis-rate-limiter.replenishRate: 10
                redis-rate-limiter.burstCapacity: 20
                key-resolver: "#{@ipKeyResolver}"

@Bean
public KeyResolver ipKeyResolver() {
    return exchange -> Mono.just(
        exchange.getRequest().getRemoteAddress().getAddress().getHostAddress());
}

六、配置中心 — Spring Cloud Config

# 客户端
spring:
  cloud:
    config:
      uri: http://localhost:8888
      profile: dev
      label: main

@RestController
@RefreshScope
public class ConfigController {
    @Value("${custom.config:default}")
    private String config;

    @GetMapping("/config")
    public String getConfig() { return config; }
}

七、常见问题

问题	解决
服务找不到	检查注册中心配置、服务名拼写
调用超时	调整 Feign/Gateway 超时配置
配置不刷新	添加 @RefreshScope + 调用 /actuator/refresh
跨域问题	网关统一配置 CORS