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聊聊spring cloud gateway的PrefixPath及StripPrefix功能

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;
		}
	}
}
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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
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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;
		}
	}
}
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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
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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。

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