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rikako-note/spring/Spring Cloud/Spring Cloud gateway.md

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# spring cloud gateway
## 项目引入spring cloud gateway
如果要在项目中引入spring cloud gateway可以在项目pom文件中添加如下依赖
```xml
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-gateway</artifactId>
```
> 如果已经在项目中引入了spring-cloud-starter-gateway的依赖但是不想启用gateway可以在配置文件中指定`spring.cloud.gateway.enabled=false`
> Spring Cloud gateway在运行时需要netty作为运行时环境并且采用Spring Webflux构建gateway在传统的基于servlet的环境中无法运行。
## Spring Cloud gateway核心概念
- Routegateway的基本构建单元Route由一个id、一个目标uripredicate集合、filter集合组成。如果聚合predicate为true那么route被匹配到
- PredicatePredicate的输入是` Spring Framework ServerWebExchange`通过该输入可以匹配http请求中的任何内容如header或请求参数等
- Filter其是GatewayFilter的实例通过特定的factory构造。在filter中可以在发送到下游请求之前或者之后对request和response进行修改。
## Spring Cloud Gateway如何工作
1. 客户端向spring cloud gateway发送请求如果Gateway Handler Mapping将请求匹配到route那么会向gateway web handler发送请求
2. gateway web handler通过filter chain对请求进行处理
## 配置route predicate factories和gateway filter factories
有两种方式来配置predicate和filtershortcuts和全展开参数
### shortcut配置方式
```yml
spring:
cloud:
gateway:
routes:
- id: after_route
uri: https://example.org
predicates:
- Cookie=mycookie,mycookievalue
```
## Route Predicate Factories
Spring Cloud Gateway包含了许多内置的route predicate factories所有的这些predicate都匹配到http请求的不同属性。可以通过逻辑运算符`and`将多个route predicate factory组合起来。
### After Route Predicate Factory
After Route Predicate Factory接收一个参数`datetime`该参数为ZonedDateTime类型该Predicate匹配发生在指定时间之后的请求。
```yml
spring:
cloud:
gateway:
routes:
- id: after_route
uri: https://example.org
predicates:
- After=2017-01-20T17:42:47.789-07:00[America/Denver]
```
该route匹配2017-01-20T17:42:47.789-07:00[America/Denver]该时间之后的任意请求
###