spring cloud gateway之filter篇

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本文出自方志朋的博客

在上一篇文章详细的介绍了Gateway的Predict，Predict决定了请求由哪一个路由处理，在路由处理之前，需要经过“pre”类型的过滤器处理，处理返回响应之后，可以由“post”类型的过滤器处理。

filter的作用和生命周期

由filter工作流程点，可以知道filter有着非常重要的作用，在“pre”类型的过滤器可以做参数校验、权限校验、流量监控、日志输出、协议转换等，在“post”类型的过滤器中可以做响应内容、响应头的修改，日志的输出，流量监控等。首先需要弄清一点为什么需要网关这一层，这就不得不说下filter的作用了。

作用

当我们有很多个服务时，比如下图中的user-service、goods-service、sales-service等服务，客户端请求各个服务的Api时，每个服务都需要做相同的事情，比如鉴权、限流、日志输出等。

在这里插入图片描述

对于这样重复的工作，有没有办法做的更好，答案是肯定的。在微服务的上一层加一个全局的权限控制、限流、日志输出的Api Gatewat服务，然后再将请求转发到具体的业务服务层。这个Api Gateway服务就是起到一个服务边界的作用，外接的请求访问系统，必须先通过网关层。

在这里插入图片描述

生命周期

Spring Cloud Gateway同zuul类似，有“pre”和“post”两种方式的filter。客户端的请求先经过“pre”类型的filter，然后将请求转发到具体的业务服务，比如上图中的user-service，收到业务服务的响应之后，再经过“post”类型的filter处理，最后返回响应到客户端。

在这里插入图片描述

与zuul不同的是，filter除了分为“pre”和“post”两种方式的filter外，在Spring Cloud Gateway中，filter从作用范围可分为另外两种，一种是针对于单个路由的gateway filter，它在配置文件中的写法同predict类似；另外一种是针对于所有路由的global gateway filer。现在从作用范围划分的维度来讲解这两种filter。

gateway filter

过滤器允许以某种方式修改传入的HTTP请求或传出的HTTP响应。过滤器可以限定作用在某些特定请求路径上。 Spring Cloud Gateway包含许多内置的GatewayFilter工厂。

GatewayFilter工厂同上一篇介绍的Predicate工厂类似，都是在配置文件application.yml中配置，遵循了约定大于配置的思想，只需要在配置文件配置GatewayFilter Factory的名称，而不需要写全部的类名，比如AddRequestHeaderGatewayFilterFactory只需要在配置文件中写AddRequestHeader，而不是全部类名。在配置文件中配置的GatewayFilter Factory最终都会相应的过滤器工厂类处理。

Spring Cloud Gateway 内置的过滤器工厂一览表如下：

在这里插入图片描述

现在挑几个常见的过滤器工厂来讲解，每一个过滤器工厂在官方文档都给出了详细的使用案例，如果不清楚的还可以在org.springframework.cloud.gateway.filter.factory看每一个过滤器工厂的源码。

AddRequestHeader GatewayFilter Factory

创建工程，引入相关的依赖,包括spring boot 版本2.0.5，spring Cloud版本Finchley，gateway依赖如下：

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

在工程的配置文件中，加入以下的配置：

server:   port: 8081 spring:   profiles:     active: add_request_header_route

spring:
cloud:
gateway:
routes:
- id: add_request_header_route
uri: http://httpbin.org:80/get
filters:
- AddRequestHeader=X-Request-Foo, Bar
predicates:
- After=2017-01-20T17:42:47.789-07:00[America/Denver]
profiles: add_request_header_route

在上述的配置中，工程的启动端口为8081，配置文件为add_request_header_route，在add_request_header_route配置中，配置了roter的id为add_request_header_route，路由地址为http://httpbin.org:80/get，该router有AfterPredictFactory，有一个filter为AddRequestHeaderGatewayFilterFactory(约定写成AddRequestHeader)，AddRequestHeader过滤器工厂会在请求头加上一对请求头，名称为X-Request-Foo，值为Bar。为了验证AddRequestHeaderGatewayFilterFactory是怎么样工作的，查看它的源码，AddRequestHeaderGatewayFilterFactory的源码如下：

 public class AddRequestHeaderGatewayFilterFactory extends AbstractNameValueGatewayFilterFactory { <span class="token annotation punctuation">@Override</span> <span class="token keyword">public</span> GatewayFilter <span class="token function">apply</span><span class="token punctuation">(</span>NameValueConfig config<span class="token punctuation">)</span> <span class="token punctuation">{</span> 	<span class="token keyword">return</span> <span class="token punctuation">(</span>exchange<span class="token punctuation">,</span> chain<span class="token punctuation">)</span> <span class="token operator">-</span><span class="token operator">&gt;</span> <span class="token punctuation">{</span> 		ServerHttpRequest request <span class="token operator">=</span> exchange<span class="token punctuation">.</span><span class="token function">getRequest</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">mutate</span><span class="token punctuation">(</span><span class="token punctuation">)</span> 				<span class="token punctuation">.</span><span class="token function">header</span><span class="token punctuation">(</span>config<span class="token punctuation">.</span><span class="token function">getName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">,</span> config<span class="token punctuation">.</span><span class="token function">getValue</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> 				<span class="token punctuation">.</span><span class="token function">build</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>  		<span class="token keyword">return</span> chain<span class="token punctuation">.</span><span class="token function">filter</span><span class="token punctuation">(</span>exchange<span class="token punctuation">.</span><span class="token function">mutate</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">request</span><span class="token punctuation">(</span>request<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">build</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> 	<span class="token punctuation">}</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>

}

由上面的代码可知，根据旧的ServerHttpRequest创建新的 ServerHttpRequest ，在新的ServerHttpRequest加了一个请求头，然后创建新的 ServerWebExchange ，提交过滤器链继续过滤。

启动工程，通过curl命令来模拟请求：

 curl localhost:8081

最终显示了从 http://httpbin.org:80/get得到了请求，响应如下：

{   "args": {},   "headers": {     "Accept": "*/*",     "Connection": "close",     "Forwarded": "proto=http;host=\"localhost:8081\";for=\"0:0:0:0:0:0:0:1:56248\"",     "Host": "httpbin.org",     "User-Agent": "curl/7.58.0",     "X-Forwarded-Host": "localhost:8081",     "X-Request-Foo": "Bar"   },   "origin": "0:0:0:0:0:0:0:1, 210.22.21.66",   "url": "http://localhost:8081/get" }

可以上面的响应可知，确实在请求头中加入了X-Request-Foo这样的一个请求头，在配置文件中配置的AddRequestHeader过滤器工厂生效。

跟AddRequestHeader过滤器工厂类似的还有AddResponseHeader过滤器工厂，在此就不再重复。

RewritePath GatewayFilter Factory

在Nginx服务启中有一个非常强大的功能就是重写路径，Spring Cloud Gateway默认也提供了这样的功能，这个功能是Zuul没有的。在配置文件中加上以下的配置：

 spring:   profiles:     active: rewritepath_route --- spring:   cloud:     gateway:       routes:       - id: rewritepath_route         uri: https://blog.csdn.net         predicates:         - Path=/foo/**         filters:         - RewritePath=/foo/(?<segment>.*), /$\{segment}   profiles: rewritepath_route

上面的配置中，所有的/foo/**开始的路径都会命中配置的router，并执行过滤器的逻辑，在本案例中配置了RewritePath过滤器工厂，此工厂将/foo/(?.*)重写为{segment}，然后转发到https://blog.csdn.net。比如在网页上请求localhost:8081/foo/forezp，此时会将请求转发到https://blog.csdn.net/forezp的页面，比如在网页上请求localhost:8081/foo/forezp/1，页面显示404，就是因为不存在https://blog.csdn.net/forezp/1这个页面。

自定义过滤器

Spring Cloud Gateway内置了19种强大的过滤器工厂，能够满足很多场景的需求，那么能不能自定义自己的过滤器呢，当然是可以的。在spring Cloud Gateway中，过滤器需要实现GatewayFilter和Ordered2个接口。写一个RequestTimeFilter，代码如下：

 public class RequestTimeFilter implements GatewayFilter, Ordered { <span class="token keyword">private</span> <span class="token keyword">static</span> <span class="token keyword">final</span> Log log <span class="token operator">=</span> LogFactory<span class="token punctuation">.</span><span class="token function">getLog</span><span class="token punctuation">(</span>GatewayFilter<span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">private</span> <span class="token keyword">static</span> <span class="token keyword">final</span> String REQUEST_TIME_BEGIN <span class="token operator">=</span> <span class="token string">"requestTimeBegin"</span><span class="token punctuation">;</span>  <span class="token annotation punctuation">@Override</span> <span class="token keyword">public</span> Mono<span class="token generics function"><span class="token punctuation">&lt;</span>Void<span class="token punctuation">&gt;</span></span> <span class="token function">filter</span><span class="token punctuation">(</span>ServerWebExchange exchange<span class="token punctuation">,</span> GatewayFilterChain chain<span class="token punctuation">)</span> <span class="token punctuation">{</span>      exchange<span class="token punctuation">.</span><span class="token function">getAttributes</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">put</span><span class="token punctuation">(</span>REQUEST_TIME_BEGIN<span class="token punctuation">,</span> System<span class="token punctuation">.</span><span class="token function">currentTimeMillis</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>     <span class="token keyword">return</span> chain<span class="token punctuation">.</span><span class="token function">filter</span><span class="token punctuation">(</span>exchange<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">then</span><span class="token punctuation">(</span>             Mono<span class="token punctuation">.</span><span class="token function">fromRunnable</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">-</span><span class="token operator">&gt;</span> <span class="token punctuation">{</span>                 Long startTime <span class="token operator">=</span> exchange<span class="token punctuation">.</span><span class="token function">getAttribute</span><span class="token punctuation">(</span>REQUEST_TIME_BEGIN<span class="token punctuation">)</span><span class="token punctuation">;</span>                 <span class="token keyword">if</span> <span class="token punctuation">(</span>startTime <span class="token operator">!=</span> null<span class="token punctuation">)</span> <span class="token punctuation">{</span>                     log<span class="token punctuation">.</span><span class="token function">info</span><span class="token punctuation">(</span>exchange<span class="token punctuation">.</span><span class="token function">getRequest</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">getURI</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">getRawPath</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">": "</span> <span class="token operator">+</span> <span class="token punctuation">(</span>System<span class="token punctuation">.</span><span class="token function">currentTimeMillis</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">-</span> startTime<span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">"ms"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>                 <span class="token punctuation">}</span>             <span class="token punctuation">}</span><span class="token punctuation">)</span>     <span class="token punctuation">)</span><span class="token punctuation">;</span>  <span class="token punctuation">}</span>  <span class="token annotation punctuation">@Override</span> <span class="token keyword">public</span> <span class="token keyword">int</span> <span class="token function">getOrder</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>     <span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>

}

在上面的代码中，Ordered中的int getOrder()方法是来给过滤器设定优先级别的，值越大则优先级越低。还有有一个filterI(exchange,chain)方法，在该方法中，先记录了请求的开始时间，并保存在ServerWebExchange中，此处是一个“pre”类型的过滤器，然后再chain.filter的内部类中的run()方法中相当于"post"过滤器，在此处打印了请求所消耗的时间。然后将该过滤器注册到router中，代码如下：

    @Bean     public RouteLocator customerRouteLocator(RouteLocatorBuilder builder) {         // @formatter:off         return builder.routes()                 .route(r -> r.path("/customer/**")                         .filters(f -> f.filter(new RequestTimeFilter())                                 .addResponseHeader("X-Response-Default-Foo", "Default-Bar"))                         .uri("http://httpbin.org:80/get")                         .order(0)                         .id("customer_filter_router")                 )                 .build();         // @formatter:on     }

重启程序，通过curl命令模拟请求：

 curl localhost:8081/customer/123

在程序的控制台输出一下的请求信息的日志：

 2018-11-16 15:02:20.177  INFO 20488 --- [ctor-http-nio-3] o.s.cloud.gateway.filter.GatewayFilter   : /customer/123: 152ms

自定义过滤器工厂

在上面的自定义过滤器中，有没有办法自定义过滤器工厂类呢?这样就可以在配置文件中配置过滤器了。现在需要实现一个过滤器工厂，在打印时间的时候，可以设置参数来决定是否打印请参数。查看GatewayFilterFactory的源码，可以发现GatewayFilterfactory的层级如下：

过滤器工厂的顶级接口是GatewayFilterFactory，我们可以直接继承它的两个抽象类来简化开发AbstractGatewayFilterFactory和AbstractNameValueGatewayFilterFactory，这两个抽象类的区别就是前者接收一个参数（像StripPrefix和我们创建的这种），后者接收两个参数（像AddResponseHeader）。

过滤器工厂的顶级接口是GatewayFilterFactory，有2个两个较接近具体实现的抽象类，分别为AbstractGatewayFilterFactory和AbstractNameValueGatewayFilterFactory，这2个类前者接收一个参数，比如它的实现类RedirectToGatewayFilterFactory；后者接收2个参数，比如它的实现类AddRequestHeaderGatewayFilterFactory类。现在需要将请求的日志打印出来，需要使用一个参数，这时可以参照RedirectToGatewayFilterFactory的写法。

 public class RequestTimeGatewayFilterFactory extends AbstractGatewayFilterFactory<RequestTimeGatewayFilterFactory.Config> { <span class="token keyword">private</span> <span class="token keyword">static</span> <span class="token keyword">final</span> Log log <span class="token operator">=</span> LogFactory<span class="token punctuation">.</span><span class="token function">getLog</span><span class="token punctuation">(</span>GatewayFilter<span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">private</span> <span class="token keyword">static</span> <span class="token keyword">final</span> String REQUEST_TIME_BEGIN <span class="token operator">=</span> <span class="token string">"requestTimeBegin"</span><span class="token punctuation">;</span> <span class="token keyword">private</span> <span class="token keyword">static</span> <span class="token keyword">final</span> String KEY <span class="token operator">=</span> <span class="token string">"withParams"</span><span class="token punctuation">;</span>  <span class="token annotation punctuation">@Override</span> <span class="token keyword">public</span> List<span class="token generics function"><span class="token punctuation">&lt;</span>String<span class="token punctuation">&gt;</span></span> <span class="token function">shortcutFieldOrder</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>     <span class="token keyword">return</span> Arrays<span class="token punctuation">.</span><span class="token function">asList</span><span class="token punctuation">(</span>KEY<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>  <span class="token keyword">public</span> <span class="token function">RequestTimeGatewayFilterFactory</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>     <span class="token keyword">super</span><span class="token punctuation">(</span>Config<span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>  <span class="token annotation punctuation">@Override</span> <span class="token keyword">public</span> GatewayFilter <span class="token function">apply</span><span class="token punctuation">(</span>Config config<span class="token punctuation">)</span> <span class="token punctuation">{</span>     <span class="token keyword">return</span> <span class="token punctuation">(</span>exchange<span class="token punctuation">,</span> chain<span class="token punctuation">)</span> <span class="token operator">-</span><span class="token operator">&gt;</span> <span class="token punctuation">{</span>         exchange<span class="token punctuation">.</span><span class="token function">getAttributes</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">put</span><span class="token punctuation">(</span>REQUEST_TIME_BEGIN<span class="token punctuation">,</span> System<span class="token punctuation">.</span><span class="token function">currentTimeMillis</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>         <span class="token keyword">return</span> chain<span class="token punctuation">.</span><span class="token function">filter</span><span class="token punctuation">(</span>exchange<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">then</span><span class="token punctuation">(</span>                 Mono<span class="token punctuation">.</span><span class="token function">fromRunnable</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">-</span><span class="token operator">&gt;</span> <span class="token punctuation">{</span>                     Long startTime <span class="token operator">=</span> exchange<span class="token punctuation">.</span><span class="token function">getAttribute</span><span class="token punctuation">(</span>REQUEST_TIME_BEGIN<span class="token punctuation">)</span><span class="token punctuation">;</span>                     <span class="token keyword">if</span> <span class="token punctuation">(</span>startTime <span class="token operator">!=</span> null<span class="token punctuation">)</span> <span class="token punctuation">{</span>                         StringBuilder sb <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">StringBuilder</span><span class="token punctuation">(</span>exchange<span class="token punctuation">.</span><span class="token function">getRequest</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">getURI</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">getRawPath</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span>                                 <span class="token punctuation">.</span><span class="token function">append</span><span class="token punctuation">(</span><span class="token string">": "</span><span class="token punctuation">)</span>                                 <span class="token punctuation">.</span><span class="token function">append</span><span class="token punctuation">(</span>System<span class="token punctuation">.</span><span class="token function">currentTimeMillis</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">-</span> startTime<span class="token punctuation">)</span>                                 <span class="token punctuation">.</span><span class="token function">append</span><span class="token punctuation">(</span><span class="token string">"ms"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>                         <span class="token keyword">if</span> <span class="token punctuation">(</span>config<span class="token punctuation">.</span><span class="token function">isWithParams</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>                             sb<span class="token punctuation">.</span><span class="token function">append</span><span class="token punctuation">(</span><span class="token string">" params:"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">append</span><span class="token punctuation">(</span>exchange<span class="token punctuation">.</span><span class="token function">getRequest</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">getQueryParams</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>                         <span class="token punctuation">}</span>                         log<span class="token punctuation">.</span><span class="token function">info</span><span class="token punctuation">(</span>sb<span class="token punctuation">.</span><span class="token function">toString</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>                     <span class="token punctuation">}</span>                 <span class="token punctuation">}</span><span class="token punctuation">)</span>         <span class="token punctuation">)</span><span class="token punctuation">;</span>     <span class="token punctuation">}</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>   <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">class</span> <span class="token class-name">Config</span> <span class="token punctuation">{</span>      <span class="token keyword">private</span> <span class="token keyword">boolean</span> withParams<span class="token punctuation">;</span>      <span class="token keyword">public</span> <span class="token keyword">boolean</span> <span class="token function">isWithParams</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>         <span class="token keyword">return</span> withParams<span class="token punctuation">;</span>     <span class="token punctuation">}</span>      <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">setWithParams</span><span class="token punctuation">(</span><span class="token keyword">boolean</span> withParams<span class="token punctuation">)</span> <span class="token punctuation">{</span>         <span class="token keyword">this</span><span class="token punctuation">.</span>withParams <span class="token operator">=</span> withParams<span class="token punctuation">;</span>     <span class="token punctuation">}</span>  <span class="token punctuation">}</span>

}

在上面的代码中 apply(Config config)方法内创建了一个GatewayFilter的匿名类，具体的实现逻辑跟之前一样，只不过加了是否打印请求参数的逻辑，而这个逻辑的开关是config.isWithParams()。静态内部类类Config就是为了接收那个boolean类型的参数服务的，里边的变量名可以随意写，但是要重写List shortcutFieldOrder()这个方法。
。

需要注意的是，在类的构造器中一定要调用下父类的构造器把Config类型传过去，否则会报ClassCastException

最后，需要在工程的启动文件Application类中，向Srping Ioc容器注册RequestTimeGatewayFilterFactory类的Bean。

     @Bean     public RequestTimeGatewayFilterFactory elapsedGatewayFilterFactory() {         return new RequestTimeGatewayFilterFactory();     }

然后可以在配置文件中配置如下：

spring:   profiles:     active: elapse_route

spring:
cloud:
gateway:
routes:
- id: elapse_route
uri: http://httpbin.org:80/get
filters:
- RequestTime=false
predicates:
- After=2017-01-20T17:42:47.789-07:00[America/Denver]
profiles: elapse_route

启动工程，在浏览器上访问localhost:8081?name=forezp，可以在控制台上看到，日志输出了请求消耗的时间和请求参数。

global filter

Spring Cloud Gateway根据作用范围划分为GatewayFilter和GlobalFilter，二者区别如下：

GatewayFilter : 需要通过spring.cloud.routes.filters 配置在具体路由下，只作用在当前路由上或通过spring.cloud.default-filters配置在全局，作用在所有路由上
GlobalFilter : 全局过滤器，不需要在配置文件中配置，作用在所有的路由上，最终通过GatewayFilterAdapter包装成GatewayFilterChain可识别的过滤器，它为请求业务以及路由的URI转换为真实业务服务的请求地址的核心过滤器，不需要配置，系统初始化时加载，并作用在每个路由上。

Spring Cloud Gateway框架内置的GlobalFilter如下：

在这里插入图片描述

上图中每一个GlobalFilter都作用在每一个router上，能够满足大多数的需求。但是如果遇到业务上的定制，可能需要编写满足自己需求的GlobalFilter。在下面的案例中将讲述如何编写自己GlobalFilter，该GlobalFilter会校验请求中是否包含了请求参数“token”，如何不包含请求参数“token”则不转发路由，否则执行正常的逻辑。代码如下：

 public class TokenFilter implements GlobalFilter, Ordered { Logger logger<span class="token operator">=</span>LoggerFactory<span class="token punctuation">.</span><span class="token function">getLogger</span><span class="token punctuation">(</span> TokenFilter<span class="token punctuation">.</span><span class="token keyword">class</span> <span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token annotation punctuation">@Override</span> <span class="token keyword">public</span> Mono<span class="token generics function"><span class="token punctuation">&lt;</span>Void<span class="token punctuation">&gt;</span></span> <span class="token function">filter</span><span class="token punctuation">(</span>ServerWebExchange exchange<span class="token punctuation">,</span> GatewayFilterChain chain<span class="token punctuation">)</span> <span class="token punctuation">{</span>     String token <span class="token operator">=</span> exchange<span class="token punctuation">.</span><span class="token function">getRequest</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">getQueryParams</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">getFirst</span><span class="token punctuation">(</span><span class="token string">"token"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>     <span class="token keyword">if</span> <span class="token punctuation">(</span>token <span class="token operator">==</span> null <span class="token operator">||</span> token<span class="token punctuation">.</span><span class="token function">isEmpty</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>         logger<span class="token punctuation">.</span><span class="token function">info</span><span class="token punctuation">(</span> <span class="token string">"token is empty..."</span> <span class="token punctuation">)</span><span class="token punctuation">;</span>         exchange<span class="token punctuation">.</span><span class="token function">getResponse</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">setStatusCode</span><span class="token punctuation">(</span>HttpStatus<span class="token punctuation">.</span>UNAUTHORIZED<span class="token punctuation">)</span><span class="token punctuation">;</span>         <span class="token keyword">return</span> exchange<span class="token punctuation">.</span><span class="token function">getResponse</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">setComplete</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>     <span class="token punctuation">}</span>     <span class="token keyword">return</span> chain<span class="token punctuation">.</span><span class="token function">filter</span><span class="token punctuation">(</span>exchange<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>  <span class="token annotation punctuation">@Override</span> <span class="token keyword">public</span> <span class="token keyword">int</span> <span class="token function">getOrder</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>     <span class="token keyword">return</span> <span class="token operator">-</span><span class="token number">100</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>

}

在上面的TokenFilter需要实现GlobalFilter和Ordered接口，这和实现GatewayFilter很类似。然后根据ServerWebExchange获取ServerHttpRequest，然后根据ServerHttpRequest中是否含有参数token，如果没有则完成请求，终止转发，否则执行正常的逻辑。

然后需要将TokenFilter在工程的启动类中注入到Spring Ioc容器中，代码如下：

 @Bean public TokenFilter tokenFilter(){         return new TokenFilter(); }

启动工程，使用curl命令请求：

 curl localhost:8081/customer/123

可以看到请没有被转发，请求被终止，并在控制台打印了如下日志：

2018-11-16 15:30:13.543  INFO 19372 --- [ctor-http-nio-2] gateway.TokenFilter                      : token is empty...

上面的日志显示了请求进入了没有传“token”的逻辑。

总结

本篇文章讲述了Spring Cloud Gateway中的过滤器，包括GatewayFilter和GlobalFilter。从官方文档的内置过滤器讲起，然后讲解自定义GatewayFilter、GatewayFilterFactory以及自定义的GlobalFilter。有很多内置的过滤器并没有讲述到，比如限流过滤器，这个我觉得是比较重要和大家关注的过滤器，将在之后的文章讲述。

参考资料

https://cloud.spring.io/spring-cloud-static/spring-cloud-gateway/2.1.0.M1/single/spring-cloud-gateway.html

https://www.jianshu.com/p/eb3a67291050

https://blog.csdn.net/qq_36236890/article/details/80822051

https://windmt.com/2018/05/08/spring-cloud-14-spring-cloud-gateway-filter

源码下载

https://github.com/forezp/SpringCloudLearning/tree/master/sc-f-gateway-predicate

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filter的作用和生命周期

作用

在这里插入图片描述

生命周期

在这里插入图片描述

gateway filter

Spring Cloud Gateway 内置的过滤器工厂一览表如下：

在这里插入图片描述

AddRequestHeader GatewayFilter Factory

创建工程，引入相关的依赖,包括spring boot 版本2.0.5，spring Cloud版本Finchley，gateway依赖如下：

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

来源：https://blog.csdn.net/djrm11/article/details/100535691

标签

gateway

Spring

spring cloud gateway之filter篇

filter的作用和生命周期

作用

生命周期

gateway filter

AddRequestHeader GatewayFilter Factory

RewritePath GatewayFilter Factory

自定义过滤器

自定义过滤器工厂

global filter

总结

更多阅读

参考资料

源码下载

filter的作用和生命周期

作用

生命周期

gateway filter

AddRequestHeader GatewayFilter Factory