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本文主要研究下spring cloud gateway的PreserveHostHeaderGatewayFilter
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 PreserveHostHeaderGatewayFilterFactory preserveHostHeaderGatewayFilterFactory() {
return new PreserveHostHeaderGatewayFilterFactory();
}
//......
}
PreserveHostHeaderGatewayFilterFactory
spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java
public class PreserveHostHeaderGatewayFilterFactory extends AbstractGatewayFilterFactory {
public GatewayFilter apply() {
return apply(o -> {});
}
public GatewayFilter apply(Object config) {
return (exchange, chain) -> {
exchange.getAttributes().put(PRESERVE_HOST_HEADER_ATTRIBUTE, true);
return chain.filter(exchange);
};
}
}
这个filter超级简单,就往exchange添加PRESERVE_HOST_HEADER_ATTRIBUTE,设置为true
NettyRoutingFilter
spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/filter/NettyRoutingFilter.java
public class NettyRoutingFilter implements GlobalFilter, Ordered {
private final HttpClient httpClient;
private final ObjectProvider<List<HttpHeadersFilter>> headersFilters;
public NettyRoutingFilter(HttpClient httpClient,
ObjectProvider<List<HttpHeadersFilter>> headersFilters) {
this.httpClient = httpClient;
this.headersFilters = headersFilters;
}
@Override
public int getOrder() {
return Ordered.LOWEST_PRECEDENCE;
}
@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
URI requestUrl = exchange.getRequiredAttribute(GATEWAY_REQUEST_URL_ATTR);
String scheme = requestUrl.getScheme();
if (isAlreadyRouted(exchange) || (!"http".equals(scheme) && !"https".equals(scheme))) {
return chain.filter(exchange);
}
setAlreadyRouted(exchange);
ServerHttpRequest request = exchange.getRequest();
final HttpMethod method = HttpMethod.valueOf(request.getMethod().toString());
final String url = requestUrl.toString();
HttpHeaders filtered = filterRequest(this.headersFilters.getIfAvailable(),
exchange);
final DefaultHttpHeaders httpHeaders = new DefaultHttpHeaders();
filtered.forEach(httpHeaders::set);
String transferEncoding = request.getHeaders().getFirst(HttpHeaders.TRANSFER_ENCODING);
boolean chunkedTransfer = "chunked".equalsIgnoreCase(transferEncoding);
boolean preserveHost = exchange.getAttributeOrDefault(PRESERVE_HOST_HEADER_ATTRIBUTE, false);
return this.httpClient.request(method, url, req -> {
final HttpClientRequest proxyRequest = req.options(NettyPipeline.SendOptions::flushOnEach)
.headers(httpHeaders)
.chunkedTransfer(chunkedTransfer)
.failOnServerError(false)
.failOnClientError(false);
if (preserveHost) {
String host = request.getHeaders().getFirst(HttpHeaders.HOST);
proxyRequest.header(HttpHeaders.HOST, host);
}
return proxyRequest.sendHeaders() //I shouldn't need this
.send(request.getBody().map(dataBuffer ->
((NettyDataBuffer)dataBuffer).getNativeBuffer()));
}).doOnNext(res -> {
ServerHttpResponse response = exchange.getResponse();
// put headers and status so filters can modify the response
HttpHeaders headers = new HttpHeaders();
res.responseHeaders().forEach(entry -> headers.add(entry.getKey(), entry.getValue()));
HttpHeaders filteredResponseHeaders = HttpHeadersFilter.filter(
this.headersFilters.getIfAvailable(), headers, exchange, Type.RESPONSE);
response.getHeaders().putAll(filteredResponseHeaders);
HttpStatus status = HttpStatus.resolve(res.status().code());
if (status != null) {
response.setStatusCode(status);
} else if (response instanceof AbstractServerHttpResponse) {
// https://jira.spring.io/browse/SPR-16748
((AbstractServerHttpResponse) response).setStatusCodeValue(res.status().code());
} else {
throw new IllegalStateException("Unable to set status code on response: " +res.status().code()+", "+response.getClass());
}
// Defer committing the response until all route filters have run
// Put client response as ServerWebExchange attribute and write response later NettyWriteResponseFilter
exchange.getAttributes().put(CLIENT_RESPONSE_ATTR, res);
}).then(chain.filter(exchange));
}
}
这里从读取PRESERVE_HOST_HEADER_ATTRIBUTE属性,没有则默认false。如果为true,则proxyRequest.header(HttpHeaders.HOST, host),传递host头部。
小结
PreserveHostHeaderGatewayFilter就是在gateway转发请求的时候把原始请求的host头部带上,转发给目标服务。默认该filter是启用的。
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