为什么使用网关？

因为多个微服务的端口不同，前端调用不方便，使用网关可以统一接收处理前端的请求，同时方便接口的集中处理，比如鉴权、聚合接口文档、限流等等..

这里使用Knife4j文档工具来实现接口文档：Knife4j框架相关的blog | Knife4j

使用

1. pom.xml引入依赖:

<dependency>
	<groupId>org.springframework.cloud</groupId>
	<artifactId>spring-cloud-starter-gateway</artifactId>
</dependency>
<!-- Nacos服务发现 -->
<dependency>
	<groupId>com.alibaba.cloud</groupId>
	<artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
</dependency>

1. 配置application.yml配置文件：

spring:
  cloud:
    gateway:
      routes:
        - id: backend-user-service
          uri: lb://backend-user-service
          predicates:
            - Path=/api/user/**
        - id: stuoj-backend-question-service
          uri: lb://backend-question-service
          predicates:
            - Path=/api/question/**
        - id: backend-comment-service
          uri: lb://backend-comment-service
          predicates:
            - Path=/api/comment/**
        - id: backend-xxx-service
          uri: lb://backend-xxx-service
          predicates:
            - Path=/api/xxx/**
    nacos:
      discovery:
        server-addr: localhost:8848
  application:
    name: backend-gateway
  main:
    web-application-type: reactive
server:
  port: 9090

聚合接口文档

目的：以一个全局的视角去集中管理里接口文档（Knife4j）

1. 先给所有的服务引入依赖。同时开启接口文档配置

<dependency>
  <groupId>com.github.xiaoymin</groupId>
  <artifactId>knife4j-openapi2-spring-boot-starter</artifactId>
  <version>4.3.0</version>
</dependency>

knife4j:
  enable: true

1. 给网关服务配置集中管理文档

<dependency>
  <groupId>com.github.xiaoymin</groupId>
  <artifactId>knife4j-gateway-spring-boot-starter</artifactId>
  <version>4.3.0</version>
</dependency>

knife4j:
  gateway:
    # ① 第一个配置，开启gateway聚合组件
    enabled: true
    # ② 第二行配置，设置聚合模式采用discover服务发现的模式
    strategy: discover
    discover:
      # ③ 第三行配置，开启discover模式
      enabled: true
      # ④ 第四行配置，聚合子服务全部为Swagger2规范的文档
      version: swagger2

 之后就可以获得所有服务的文档了：

 网关集中解决跨域

在gateway的模块下创建一个confg配置代码：

package com.stukk.stuojbackendgateway.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.cors.CorsConfiguration;
import org.springframework.web.cors.reactive.CorsWebFilter;
import org.springframework.web.cors.reactive.UrlBasedCorsConfigurationSource;
import org.springframework.web.util.pattern.PathPatternParser;

import java.util.Arrays;

/**
 * @Author: stukk
 * @Description: 跨域处理
 * @DateTime: 2023-12-07 19:04
 **/
@Configuration
public class CrosConfig {

    @Bean
    public CorsWebFilter corsWebFilter(){
        CorsConfiguration corsConfiguration = new CorsConfiguration();
        corsConfiguration.addAllowedMethod("*");
        corsConfiguration.setAllowCredentials(true);
        corsConfiguration.setAllowedOriginPatterns(Arrays.asList("*"));
        corsConfiguration.addAllowedHeader("*");
        UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource(new PathPatternParser());
        source.registerCorsConfiguration("/**",corsConfiguration);
        return new CorsWebFilter(source);
    }

}

网关实现权限校验

使用拦截器Filter，拦截路径并判断权限

package com.stukk.stuojbackendgateway.filter;

import cn.hutool.core.text.AntPathMatcher;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.GlobalFilter;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferFactory;
import org.springframework.http.HttpStatus;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Mono;

import java.nio.charset.StandardCharsets;

/**
 * @Author: stukk
 * @Description: 网关拦截器
 * @DateTime: 2023-12-07 19:16
 **/
@Component
public class GlobalAuthFilter implements GlobalFilter {

    private AntPathMatcher antPathMatcher = new AntPathMatcher();

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        ServerHttpRequest request = exchange.getRequest();
        String path = request.getURI().getPath();
//        判断是不是内部调用，拦截内部调用
        if(antPathMatcher.match("**/inner/**",path)){
            ServerHttpResponse response = exchange.getResponse();
            response.setStatusCode(HttpStatus.FORBIDDEN);
            DataBufferFactory dataBufferFactory = response.bufferFactory();
            DataBuffer dataBuffer = dataBufferFactory.wrap("无权限".getBytes(StandardCharsets.UTF_8));
            return response.writeWith(Mono.just(dataBuffer));
        }
        return chain.filter(exchange);
    }
}