SpringCloud之Gateway原理解析（一）--准备

一 准备阶段

　　这部分比较琐碎，基本上我想到了什么就会写什么

　　1 gateway的web实现是webFlux，所以Gateway的工程不能引入SpringMvc

　　2 GatewayLoadBalancerClientAutoConfiguration这个是gateway负载均衡的过滤器实现的加载，他将LoadBalancerClientFilter 注入到了容器中　

@Configuration

@ConditionalOnClass({LoadBalancerClient.class, RibbonAutoConfiguration.class, DispatcherHandler.class})

@AutoConfigureAfter(RibbonAutoConfiguration.class)

public class GatewayLoadBalancerClientAutoConfiguration {

 // GlobalFilter beans

 @Bean

 @ConditionalOnBean(LoadBalancerClient.class)

 public LoadBalancerClientFilter loadBalancerClientFilter(LoadBalancerClient client) {

  return new LoadBalancerClientFilter(client);

 }

}

public class LoadBalancerClientFilter implements GlobalFilter, Ordered {

    /**
     * Filter order for {@link LoadBalancerClientFilter}.
     */
    public static final int LOAD_BALANCER_CLIENT_FILTER_ORDER = 10100;

    private static final Log log = LogFactory.getLog(LoadBalancerClientFilter.class);

    protected final LoadBalancerClient loadBalancer;

    private LoadBalancerProperties properties;

LoadBalancerClient的实现类就是RibbonLoadBalancerClient，做负载均衡都离不开ribbon3 
3 最重要的 GatewayAutoConfiguration
　　这个类实在是太大了，内容也很多，比如各种断言过滤拦截的工厂类都在这里，我这里只列出部分源码看一下PropertiesRouteDefinitionLocator，它是负责把配置文件里的路由规则
　　转成对象的类。

public class GatewayAutoConfiguration {

    @Bean
    public StringToZonedDateTimeConverter stringToZonedDateTimeConverter() {
        return new StringToZonedDateTimeConverter();
    }

    @Bean
    public RouteLocatorBuilder routeLocatorBuilder(
            ConfigurableApplicationContext context) {
        return new RouteLocatorBuilder(context);
    }

    @Bean
    @ConditionalOnMissingBean
    public PropertiesRouteDefinitionLocator propertiesRouteDefinitionLocator(
            GatewayProperties properties) {
        return new PropertiesRouteDefinitionLocator(properties);
    }

首先对比下我们的配置文件

spring:
  application:
    name: sc-gateway-server
  cloud:
    gateway:
      discovery:
        locator:
          enabled: false
          lowerCaseServiceId: true
      routes:
      - id: service-hi
        uri: lb://SERVICE-HI
        predicates:
          - Path=/demo/**, /api-gateway/**, /hi/**
        filters:
#          - StripPrefix=1
#          - RequestTime=true
          #- RewritePath=/api-gateway/(?<segment>/?.*), /${segment}
#http://localhost:8081/api-gateway/demo/hi?name=mxz123 按照这个url请求就可以，之前我一直不成功，因为cloud Finchley版本有bug
#          - RewritePath=/api-gateway/demo, /demo
#          - StripPrefix=1
          - name: RequestRateLimiter
            args:
              redis-rate-limiter.replenishRate: 1
              redis-rate-limiter.burstCapacity: 2
              key-resolver: "#{@pathKeyResolver}"

RouteDefinitionRouteLocator

能够看出gateway中的路由信息正是我们的配置文件里配的