聊聊spring cloud gateway的PrefixPath及StripPrefix功能

序

本文主要研究一下spring cloud gateway的PrefixPath及StripPrefix功能

PrefixPathGatewayFilterFactory

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

public class PrefixPathGatewayFilterFactory extends AbstractGatewayFilterFactory<PrefixPathGatewayFilterFactory.Config> {

    private static final Log log = LogFactory.getLog(PrefixPathGatewayFilterFactory.class);

    public static final String PREFIX_KEY = "prefix";

    public PrefixPathGatewayFilterFactory() {
        super(Config.class);
    }

    @Override
    public List<String> shortcutFieldOrder() {
        return Arrays.asList(PREFIX_KEY);
    }

    @Override
    public GatewayFilter apply(Config config) {
        return (exchange, chain) -> {

            boolean alreadyPrefixed = exchange.getAttributeOrDefault(GATEWAY_ALREADY_PREFIXED_ATTR, false);
            if (alreadyPrefixed) {
                return chain.filter(exchange);
            }
            exchange.getAttributes().put(GATEWAY_ALREADY_PREFIXED_ATTR, true);

            ServerHttpRequest req = exchange.getRequest();
            addOriginalRequestUrl(exchange, req.getURI());
            String newPath = config.prefix + req.getURI().getRawPath();

            ServerHttpRequest request = req.mutate()
                    .path(newPath)
                    .build();

            exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, request.getURI());

            if (log.isTraceEnabled()) {
                log.trace("Prefixed URI with: "+config.prefix+" -> "+request.getURI());
            }

            return chain.filter(exchange.mutate().request(request).build());
        };
    }

    public static class Config {
        private String prefix;

        public String getPrefix() {
            return prefix;
        }

        public void setPrefix(String prefix) {
            this.prefix = prefix;
        }
    }
}

可以看到这里使用config的prefix构造newPath，然后构造新的ServerHttpRequest

实例

spring:
  cloud:
    gateway:
      routes:
      - id: prefixpath_route
        uri: http://example.org
        filters:
        - PrefixPath=/mypath

比如：请求/hello，最后转发到目标服务的路径变为/mypath/hello

StripPrefixGatewayFilterFactory

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

/**
 * This filter removes the first part of the path, known as the prefix, from the request
 * before sending it downstream
 * @author Ryan Baxter
 */
public class StripPrefixGatewayFilterFactory extends AbstractGatewayFilterFactory<StripPrefixGatewayFilterFactory.Config> {

    public static final String PARTS_KEY = "parts";

    public StripPrefixGatewayFilterFactory() {
        super(Config.class);
    }

    @Override
    public List<String> shortcutFieldOrder() {
        return Arrays.asList(PARTS_KEY);
    }

    @Override
    public GatewayFilter apply(Config config) {
        return (exchange, chain) ->  {
            ServerHttpRequest request = exchange.getRequest();
            addOriginalRequestUrl(exchange, request.getURI());
            String path = request.getURI().getRawPath();
            String newPath = "/" + Arrays.stream(StringUtils.tokenizeToStringArray(path, "/"))
                    .skip(config.parts).collect(Collectors.joining("/"));
            ServerHttpRequest newRequest = request.mutate()
                    .path(newPath)
                    .build();

            exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, newRequest.getURI());

            return chain.filter(exchange.mutate().request(newRequest).build());
        };
    }

    public static class Config {
        private int parts;

        public int getParts() {
            return parts;
        }

        public void setParts(int parts) {
            this.parts = parts;
        }
    }
}

可以看到这里的parts指定要去除的前缀的个数，然后使用stream的skip来去除掉相应前缀，然后得到newPath，构造newRequest

实例

spring:
  cloud:
    gateway:
      routes:
      - id: nameRoot
        uri: http://nameservice
        predicates:
        - Path=/name/**
        filters:
        - StripPrefix=2

比如，请求/name/bar/foo，去除掉前面两个前缀之后，最后转发到目标服务的路径为/foo

小结

PrefixPathGatewayFilterFactory及StripPrefixGatewayFilterFactory是一对针对请求url前缀进行处理的filter工厂，前者添加prefix，后者去除prefix。

doc

• 112.5 PrefixPath GatewayFilter Factory
• 112.18 StripPrefix GatewayFilter Factory