1.为什么需要网关

2.操作

（1）创建项目引入依赖服务发现和gateway网关依赖

pom
    <dependencies>
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-gateway</artifactId>
        </dependency>
    </dependencies>

(2)实现请求路由功能

config
spring:
  application:
    name: gateway
  cloud:
    nacos:
      server-addr: localhost:80
    gateway:
      routes:
        - id: user-service
          uri: lb://userservice # 路由的目标地址
          predicates:
            - Path=/user/** # 判断路径是否是user开头
        - id: order-service
          uri: lb://orderservice
          predicates:
            - Path=/order/**
server:
  port: 10010

(3)总结

（4）路由断言工厂

（5）过滤器工厂

代码示例

config
    gateway:
      routes:
        - id: user-service
          uri: lb://userservice # 路由的目标地址
          predicates:
            - Path=/user/** # 判断路径是否是user开头
        - id: order-service
          uri: lb://orderservice
          predicates:
            - Path=/order/**
          filters:
            - AddRequestHeader=Truth,Hello world # 添加的过滤器

向所有微服务添加过滤器 默认过滤器 全局过滤器 编写代码自定义过滤逻辑 实现golabalFilter接口 案例：

java
package cn.itcast.gateway;

import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.GlobalFilter;
import org.springframework.core.annotation.Order;
import org.springframework.http.HttpStatus;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.stereotype.Component;
import org.springframework.util.MultiValueMap;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Mono;



@Order(-1) // 定义过滤器的顺序 默认最低 数字越小最先执行
@Component
public class AuthorizeFilter implements GlobalFilter {
    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {

//        1.获取请求参数
        ServerHttpRequest request =exchange.getRequest();
        MultiValueMap<String,String> params= request.getQueryParams();
//        2获取参数中的authorization
        String auth = params.getFirst("authorization");
        if ("admin".equals(auth)){
            return chain.filter(exchange); // 放行
        }
        // 否 拦截

        // 设置状态码
        exchange.getResponse().setStatusCode(HttpStatus.UNAUTHORIZED);
        // 拦截请求
        return exchange.getResponse().setComplete();
        //
    }
}

过滤器执行顺序 1.当前路由过滤器 2.DefaultFilter 3.GlobalFilter

（6）跨域问题