环境 SpringCloud:Finchley.RELEASE SpringBoot：2.0.0.RELEASE JDK：1.8

1. 核心概念

1. 路由（route) 路由是网关中最基础的部分，路由信息包括一个ID、一个目的URI、一组断言工厂、一组Filter组成。如果断言为真，则说明请求的URL和配置的路由匹配。
2. 断言(predicates) Java8中的断言函数，SpringCloud Gateway中的断言函数类型是Spring5.0框架中的ServerWebExchange。断言函数允许开发者去定义匹配Http request中的任何信息，比如请求头和参数等。
3. 过滤器（Filter) SpringCloud Gateway中的filter分为Gateway FilIer和Global Filter。Filter可以对请求和响应进行处理。

2. 入门案例

2.1 搭建环境

1. 创建工程导入坐标

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

2. 配置启动类

@SpringBootApplication
public class GatewayServerApplication {

    public static void main(String[] args) {
        SpringApplication.run(GatewayServerApplication.class, args);
    }
}

3. 编写配置文件

spring:
  application:
    name: microservice-gateway
  cloud:
    gateway:
      routes: #设置路由：路由id、路由打微服务的uri、断言
      - id: microservice-provider #路由ID，全局唯一
        uri: http://127.0.0.1:8001 #目标微服务的请求地址和端口
        predicates:
        - Path=/provider/**  #路由条件，采用path路由规则

2.2 路由规则

内置断言：

2.2.1 The after route predicate

spring:
  cloud:
    gateway:
      routes:
      - id: after_route
        uri: https://example.org
        predicates:
        - After=2017-01-20T17:42:47.789-07:00[America/Denver]

2.2.2 the before route predicate

spring:
  cloud:
    gateway:
      routes:
      - id: before_route
        uri: https://example.org
        predicates:
        - Before=2017-01-20T17:42:47.789-07:00[America/Denver]

2.2.3 the between route predicate

spring:
  cloud:
    gateway:
      routes:
      - id: between_route
        uri: https://example.org
        predicates:
        - Between=2017-01-20T17:42:47.789-07:00[America/Denver], 2017-01-21T17:42:47.789-07:00[America/Denver]

2.2.4 the cookie route predicate

spring:
  cloud:
    gateway:
      routes:
      - id: cookie_route
        uri: https://example.org
        predicates:
        - Cookie=chocolate, ch.p

2.2.5 the header route predicate

spring:
  cloud:
    gateway:
      routes:
      - id: header_route
        uri: https://example.org
        predicates:
        - Header=X-Request-Id, \d+

2.2.6 the host route predicate

spring:
  cloud:
    gateway:
      routes:
      - id: host_route
        uri: https://example.org
        predicates:
        - Host=**.somehost.org,**.anotherhost.org

2.2.7 the method route predicate

spring:
  cloud:
    gateway:
      routes:
      - id: method_route
        uri: https://example.org
        predicates:
        - Method=GET,POST

2.2.8 the path route predicate

Http请求路径匹配

spring:
  cloud:
    gateway:
      routes:
      - id: path_route
        uri: https://example.org
        predicates:
        - Path=/red/{segment},/blue/{segment}

2.2.9 the query route predicate

http请求参数匹配

1. 请求参数包含green

spring:
  cloud:
    gateway:
      routes:
      - id: query_route
        uri: https://example.org
        predicates:
        - Query=green

2. 请求参数reg正则匹配gree.

spring:
  cloud:
    gateway:
      routes:
      - id: query_route
        uri: https://example.org
        predicates:
        - Query=red, gree.

2.2.10 the remoteaddress route predicate

spring:
  cloud:
    gateway:
      routes:
      - id: remoteaddr_route
        uri: https://example.org
        predicates:
        - RemoteAddr=192.168.1.1/24

2.2.11 the weight route predicate

根据权重负载

spring:
  cloud:
    gateway:
      routes:
      - id: weight_high
        uri: https://weighthigh.org
        predicates:
        - Weight=group1, 8
      - id: weight_low
        uri: https://weightlow.org
        predicates:
        - Weight=group1, 2

2.3 动态路由

1. 导入坐标

        <!--eureka client-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>

2. 修改启动类（可以不修改，eureka client配置application.yml的注册中心地址默认会开启服务发现）

@SpringBootApplication
@EnableDiscoveryClient
public class GatewayServerApplication {

    public static void main(String[] args) {
        SpringApplication.run(GatewayServerApplication.class, args);
    }
}

3. 修改配置文件

spring:
  application:
    name: microservice-gateway
  cloud:
    gateway:
      routes: #设置路由：路由id、路由打微服务的uri、断言
      - id: microservice-provider #路由ID，全局唯一
#        uri: http://127.0.0.1:8001 #目标微服务的请求地址和端口
        uri: lb://microservice-provider  # lb://微服务名 根据微服务名称从注册中心获取地址
        predicates:
        - Path=/provider/**  #路由条件，采用path路由规则


##eureka配置信息
eureka:
  client:
    service-url:  #注册中心地址列表
      defaultZone: http://server7001:7001/eureka/,http://server7002:7002/eureka/,http://server7003:7003/eureka/
  instance:
    instance-id: microservice-gateway6101  # 自定义控制台中微服务名称
    prefer-ip-address: true  #eureka控制访问路径显示ip

#解决eureka控制台中的Info页面错误问题
info:
  app.name: com.xyz.microservice
  build.artifactId: $project.artifactId$ #使用maven内置变量project.artifactId和project.version完成对变量的赋值
  build.version: $project.version$

2.4 重写转发路径

通过RewritePath的过滤器，实现把请求路径重写成实际后端微服务的地址

spring:
  application:
    name: microservice-gateway
  cloud:
    gateway:
      routes: #设置路由：路由id、路由打微服务的uri、断言
      - id: microservice-provider #路由ID，全局唯一
#        uri: http://127.0.0.1:8001 #目标微服务的请求地址和端口
        uri: lb://microservice-provider  # lb://微服务名 根据微服务名称从注册中心获取地址
        predicates:
        - Path=/product/**  #路由条件，采用path路由规则
        filters:  # 实现重写转发路径： http://localhost:6101/product/provider/list --> http://localhost:6101/provider/list
        - RewritePath=/product/(?<segment>.*), /$\{segment}

2.5 设置通过微服务名称转发

spring.cloud.gateway.discovery.locator.enabled=true开启后默认通过微服务名称进行匹配

spring:
  application:
    name: microservice-gateway
  cloud:
    gateway:
      discovery:
        locator:
          enabled: true  #开启通过微服务名称默认进行转发规则：如http://localhost:6101/microservice-provider/provider/list 
          lower-case-service-id: true  #微服务名称通过小写的方式请求

todo 开启spring.cloud.gateway.discovery.locator.enabled=true，启动服务报错

代码示例