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本文主要研究一下spring cloud的RequestHeaderToRequestUriGatewayFilter

GatewayAutoConfiguration

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java

@Configuration@ConditionalOnProperty(name = "spring.cloud.gateway.enabled", matchIfMissing = true)@EnableConfigurationProperties@AutoConfigureBefore(HttpHandlerAutoConfiguration.class)@AutoConfigureAfter({GatewayLoadBalancerClientAutoConfiguration.class, GatewayClassPathWarningAutoConfiguration.class})@ConditionalOnClass(DispatcherHandler.class)public class GatewayAutoConfiguration {    //......    @Bean    public RequestHeaderToRequestUriGatewayFilterFactory requestHeaderToRequestUriGatewayFilterFactory() {        return new RequestHeaderToRequestUriGatewayFilterFactory();    }    //......}

RequestHeaderToRequestUriGatewayFilterFactory

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/filter/factory/RequestHeaderToRequestUriGatewayFilterFactory.java

/** * This filter changes the request uri by a request header * * @author Toshiaki Maki */public class RequestHeaderToRequestUriGatewayFilterFactory extends        AbstractChangeRequestUriGatewayFilterFactory
    
      {    private final Logger log = LoggerFactory            .getLogger(RequestHeaderToRequestUriGatewayFilterFactory.class);    public RequestHeaderToRequestUriGatewayFilterFactory() {        super(NameConfig.class);    }    @Override    public List
     
       shortcutFieldOrder() {        return Arrays.asList(NAME_KEY);    }    @Override    protected Optional
      
        determineRequestUri(ServerWebExchange exchange,            NameConfig config) {        String requestUrl = exchange.getRequest().getHeaders().getFirst(config.getName());        return Optional.ofNullable(requestUrl).map(url -> {            try {                return new URL(url).toURI();            }            catch (MalformedURLException | URISyntaxException e) {                log.info("Request url is invalid : url={}, error={}", requestUrl,                        e.getMessage());                return null;            }        });    }}
      
     
    

• 主要是继承了AbstractChangeRequestUriGatewayFilterFactory
• 这里重写了determineRequestUri方法，根据配置的header取出url

AbstractChangeRequestUriGatewayFilterFactory

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/filter/factory/AbstractChangeRequestUriGatewayFilterFactory.java

/** * This filter changes the request uri by * {@link #determineRequestUri(ServerWebExchange, T)} logic. * * @author Toshiaki Maki */public abstract class AbstractChangeRequestUriGatewayFilterFactory
    
             extends AbstractGatewayFilterFactory
     
       {    private final int order;    public AbstractChangeRequestUriGatewayFilterFactory(Class
      
        clazz, int order) {        super(clazz);        this.order = order;    }    public AbstractChangeRequestUriGatewayFilterFactory(Class
       
         clazz) {        this(clazz, RouteToRequestUrlFilter.ROUTE_TO_URL_FILTER_ORDER + 1);    }    protected abstract Optional
        
          determineRequestUri(ServerWebExchange exchange,            T config);    public GatewayFilter apply(T config) {        return new OrderedGatewayFilter((exchange, chain) -> {            Optional
         
           uri = this.determineRequestUri(exchange, config); uri.ifPresent(u -> { Map
          
            attributes = exchange.getAttributes(); attributes.put(GATEWAY_REQUEST_URL_ATTR, u); }); return chain.filter(exchange); }, this.order); }}
          
         
        
       
      
     
    

这里就是取出url，设置GATEWAY_REQUEST_URL_ATTR，然后GlobalFilter里头会根据这个属性取出url出来使用

实例

spring:  cloud:    gateway:      enabled: true      discovery:        locator:          enabled: true      routes:      - id: demo        uri: http://wwww.baidu.com        predicates:        - Path=/baidu/**        filters:        - RequestHeaderToRequestUri=X-New-Url

比如这里设置了根据X-New-Url来进行新的url路由，那么执行下面这段代码，则请求/baidu的则会转向请求163的

curl -i -H "X-New-Url: http://news.163.com" localhost:10000/baidu

小结

RequestHeaderToRequestUriGatewayFilter实现的功能就是根据配置文件指定的header来读取新的路由的url。比较强大，可以用在灰度、生产定位问题等场景上。

doc