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本文主要研究一下spring cloud gateway的ForwardedHeadersFilter

GatewayAutoConfiguration

spring-cloud-gateway-core-2.0.0.RC1-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	@ConditionalOnProperty(name = "spring.cloud.gateway.forwarded.enabled", matchIfMissing = true)	public ForwardedHeadersFilter forwardedHeadersFilter() {		return new ForwardedHeadersFilter();	}	//......}复制代码

ForwardedHeadersFilter

spring-cloud-gateway-core-2.0.0.RC1-sources.jar!/org/springframework/cloud/gateway/filter/headers/ForwardedHeadersFilter.java

public class ForwardedHeadersFilter implements HttpHeadersFilter, Ordered {	public static final String FORWARDED_HEADER = "Forwarded";	@Override	public int getOrder() {		return 0;	}	@Override	public HttpHeaders filter(HttpHeaders input, ServerWebExchange exchange) {		ServerHttpRequest request = exchange.getRequest();		HttpHeaders original = input;		HttpHeaders updated = new HttpHeaders();		// copy all headers except Forwarded		original.entrySet().stream()				.filter(entry -> !entry.getKey().toLowerCase().equalsIgnoreCase(FORWARDED_HEADER))				.forEach(entry -> updated.addAll(entry.getKey(), entry.getValue()));		List
    
      forwardeds = parse(original.get(FORWARDED_HEADER));		for (Forwarded f : forwardeds) {			updated.add(FORWARDED_HEADER, f.toString());		}		//TODO: add new forwarded		URI uri = request.getURI();		String host = original.getFirst(HttpHeaders.HOST);		Forwarded forwarded = new Forwarded()				.put("host", host)				.put("proto", uri.getScheme());		InetSocketAddress remoteAddress = request.getRemoteAddress();		if (remoteAddress != null) {			String forValue = remoteAddress.getAddress().getHostAddress();			int port = remoteAddress.getPort();			if (port >= 0) {				forValue = forValue + ":" + port;			}			forwarded.put("for", forValue);		}		// TODO: support by?		updated.add(FORWARDED_HEADER, forwarded.toHeaderValue());		return updated;	}	/* for testing */ static List
     
       parse(List
      
        values) {		ArrayList
       
         forwardeds = new ArrayList<>();		if (CollectionUtils.isEmpty(values)) {			return forwardeds;		}    	for (String value : values) {			Forwarded forwarded = parse(value);			forwardeds.add(forwarded);		}		return forwardeds;	}	/* for testing */ static Forwarded parse(String value) {		String[] pairs = StringUtils.tokenizeToStringArray(value, ";");		LinkedCaseInsensitiveMap
        
          result = splitIntoCaseInsensitiveMap(pairs);		if (result == null) return null;		Forwarded forwarded = new Forwarded(result);		return forwarded;	}	@Nullable	/* for testing */ static LinkedCaseInsensitiveMap
         
           splitIntoCaseInsensitiveMap(String[] pairs) { if (ObjectUtils.isEmpty(pairs)) { return null; } LinkedCaseInsensitiveMap
          
            result = new LinkedCaseInsensitiveMap<>(); for (String element : pairs) { String[] splittedElement = StringUtils.split(element, "="); if (splittedElement == null) { continue; } result.put(splittedElement[0].trim(), splittedElement[1].trim()); } return result; }}复制代码
          
         
        
       
      
     
    

这个filter首先拷贝了请求的header，然后将请求中的Forwarded提取出来，解析成一个个Forwarded对象，添加到新的HttpHeaders中。除此之外，还补充了一个转发信息的Forwarded(host,proto,for)

Forwarded

语法

Forwarded: by=
    
     ; for=
     
      ; host=
      
       ; proto=
       
        复制代码
       
      
     
    

• by= 该请求进入到代理服务器的接口。
• for= 发起请求的客户端以及代理链中的一系列的代理服务器。
• host= 代理接收到的 Host首部的信息。
• proto=<http|https> 表示发起请求时采用的何种协议（通常是 "http" 或者 "https"）。

实例

Forwarded: for=192.0.2.60; proto=http; by=203.0.113.43Forwarded: proto=http;host="localhost:10000";for="0:0:0:0:0:0:0:1:56443"复制代码

对象

static class Forwarded {		private static final char EQUALS = '=';		private static final char SEMICOLON = ';';		private final Map
    
      values;		public Forwarded() {			this.values = new HashMap<>();		}		public Forwarded(Map
     
       values) {			this.values = values;		}		public Forwarded put(String key, String value) {			this.values.put(key, quoteIfNeeded(value));			return this;		}		private String quoteIfNeeded(String s) {			if (s.contains(":")) { //TODO: broaded quote				return "\""+s+"\"";			}			return s;		}		public String get(String key) {			return this.values.get(key);		}		/* for testing */ Map
      
        getValues() {			return this.values;		}		@Override		public String toString() {			return "Forwarded{" +					"values=" + this.values +					'}';		}		public String toHeaderValue() {			StringBuilder builder = new StringBuilder();			for (Map.Entry
       
         entry : this.values.entrySet()) {				if (builder.length() > 0) {					builder.append(SEMICOLON);				}				builder.append(entry.getKey())						.append(EQUALS)						.append(entry.getValue());			}			return builder.toString();		}	}复制代码
       
      
     
    

小结

RFC 7239(June 2014)提出了一个标准化的Forwarded头部，来携带反向代理的基本信息，用于替代X-Forwarded系列及X-Real-IP等非标准化的头部。而ForwardedHeadersFilter便是提供了Forwarded头部的转发支持，目前经过gateway的请求会带上一个转发信息的Forwarded(host,proto,for)。

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