SpringCloud：Spring Cloud Gateway中如何定制filter实现自定义路由

梦里梦外; 2022-11-14 10:24 225阅读 0赞

Spring Cloud Gateway中提供的默认filter有时不能满足实际的业务需求，因此很多时候需要使用定制的filter。

在Spring Cloud Gateway中，predicate用于定义请求需要满足什么条件才能对它继续进行处理，filter用于定义对请求进行怎样的处理，uri用于定义处理后的请求要转发到什么地址。

filter执行的顺序是有优先级的，优先级越高则在pre阶段执行顺序越靠前，而在post阶段执行顺序越靠后。在Spring Cloud Gateway中会为每个filter设置一个order值，order值越大则优先级越低，order值起小优先级越高。

Spring Cloud Gateway中有两个非常重要的GlobalFilter：

<table style="width:500px;"> 
 <tbody> 
  <tr> 
   <td style="width:172px;">filter名称</td> 
   <td style="width:166px;">作用</td> 
   <td style="width:161px;">优先级</td> 
  </tr> 
  <tr> 
   <td style="width:172px;">RouteToRequestUrlFilter</td> 
   <td style="width:166px;">生成最终转发到的uri</td> 
   <td style="width:161px;">10000</td> 
  </tr> 
  <tr> 
   <td style="width:172px;">NettyRoutingFilter</td> 
   <td style="width:166px;">转发报文</td> 
   <td style="width:161px;">Integer.MAX_VALUE</td> 
  </tr> 
 </tbody> 
</table>

例如要实现根据特定标识将请求转发到指定uri的功能，则定制的filter的优先级要在RouteToRequestUrlFilter和NettyRoutingFilter之间，下面提供一个例子：

pom.xml

<properties>
    	<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    	<maven.compiler.source>1.8</maven.compiler.source>
    	<maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    
    <dependencies>
    	<dependency>
    		<groupId>org.springframework.boot</groupId>
    		<artifactId>spring-boot-starter-webflux</artifactId>
    		<version>2.4.4</version>
    	</dependency>
    	<dependency>
    		<groupId>org.springframework.cloud</groupId>
    		<artifactId>spring-cloud-starter-gateway</artifactId>
    		<version>3.0.2</version>
    	</dependency>
    </dependencies>

application.properties

server.port=8070
    spring.application.name=gateway_server
    
    # unit: ms
    spring.cloud.gateway.httpclient.connect-timeout=10000
    spring.cloud.gateway.httpclient.response-timeout=5s

java代码

import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration;
    import org.springframework.cloud.gateway.route.RouteLocator;
    import org.springframework.cloud.gateway.route.builder.RouteLocatorBuilder;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    
    @Configuration
    @SpringBootApplication
    @EnableAutoConfiguration(exclude = { ErrorMvcAutoConfiguration.class })
    public class SpringCloudGatewayApplication {
    	@Autowired
    	private CustomerFilter filter;
    
    	public static void main(String[] args) {
    		SpringApplication.run(SpringCloudGatewayApplication.class, args);
    	}
    
    	@Bean
    	public RouteLocator myRoutes(RouteLocatorBuilder builder) {
    		return builder.routes().route(p -> p.path("/**").filters(f -> f.filter(filter)).uri("no://op")).build();
    	}
    
    }

import reactor.core.publisher.Mono;
    
    @Component
    public class CustomerFilter implements GatewayFilter, Ordered {
    
    	@Override
    	public int getOrder() {
    		return RouteToRequestUrlFilter.ROUTE_TO_URL_FILTER_ORDER + 1;
    	}
    
    	@Override
    	public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
    		String newUrl = null;
    		String serviceName = "";
    
    		List<String> serviceHeaderList = exchange.getRequest().getHeaders().getValuesAsList("serviceName");
    
    		if (serviceHeaderList.contains("s1")) {
    			newUrl = "http://127.0.0.1:9090/TestWebApp/testServlet";
    			serviceName = "s1";
    		} else if (serviceHeaderList.contains("s2")) {
    			newUrl = "http://127.0.0.1:9090/TestWebApp/regionServlet?flag=list";
    			serviceName = "s2";
    		}
    
    		try {
    			exchange.getAttributes().put(ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR, new URI(newUrl));
    		} catch (URISyntaxException e) {
    			e.printStackTrace();
    		}
    
    		Mono<Void> ret = chain.filter(exchange);
    
    		exchange.getResponse().getHeaders().add("doWork", serviceName + " ok");
    
    		return ret;
    	}
    }

以上代码中可以看到，会根据请求头中serviceName对应的值转到不同的uri，同时把order的值设置成比RouteToRequestUrlFilter的order的值大1，这样CustomerFilter在pre阶段就会在RouteToRequestUrlFilter之后执行。