Fix potential memory leak when using ReadBodyRoutePredicateFactory

Fixes gh-3465

Author: qnnn

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/filter/RemoveCachedBodyFilter.java

@@ -16,37 +16,17 @@
 
 package org.springframework.cloud.gateway.filter;
 
-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
 import reactor.core.publisher.Mono;
 
+import org.springframework.cloud.gateway.support.ServerWebExchangeUtils;
 import org.springframework.core.Ordered;
-import org.springframework.core.io.buffer.PooledDataBuffer;
 import org.springframework.web.server.ServerWebExchange;
 
-import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.CACHED_REQUEST_BODY_ATTR;
-
 public class RemoveCachedBodyFilter implements GlobalFilter, Ordered {
 
-	private static final Log log = LogFactory.getLog(RemoveCachedBodyFilter.class);
-
 	@Override
 	public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
-		return chain.filter(exchange).doFinally(s -> {
-			Object attribute = exchange.getAttributes().remove(CACHED_REQUEST_BODY_ATTR);
-			if (attribute != null && attribute instanceof PooledDataBuffer) {
-				PooledDataBuffer dataBuffer = (PooledDataBuffer) attribute;
-				if (dataBuffer.isAllocated()) {
-					if (log.isTraceEnabled()) {
-						log.trace("releasing cached body in exchange attribute");
-					}
-					// ensure proper release
-					while (!dataBuffer.release()) {
-						// release() counts down until zero, will never be infinite loop
-					}
-				}
-			}
-		});
+		return chain.filter(exchange).doFinally(s -> ServerWebExchangeUtils.clearCachedRequestBody(exchange));
 	}
 
 	@Override

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/handler/RoutePredicateHandlerMapping.java

@@ -24,6 +24,7 @@
 import org.springframework.cloud.gateway.config.GlobalCorsProperties;
 import org.springframework.cloud.gateway.route.Route;
 import org.springframework.cloud.gateway.route.RouteLocator;
+import org.springframework.cloud.gateway.support.ServerWebExchangeUtils;
 import org.springframework.core.env.Environment;
 import org.springframework.web.cors.CorsConfiguration;
 import org.springframework.web.reactive.handler.AbstractHandlerMapping;
@@ -99,6 +100,7 @@ protected Mono<?> getHandlerInternal(ServerWebExchange exchange) {
 				})
 				.switchIfEmpty(Mono.empty().then(Mono.fromRunnable(() -> {
 					exchange.getAttributes().remove(GATEWAY_PREDICATE_ROUTE_ATTR);
+					ServerWebExchangeUtils.clearCachedRequestBody(exchange);
 					if (logger.isTraceEnabled()) {
 						logger.trace("No RouteDefinition found for [" + getExchangeDesc(exchange) + "]");
 					}

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/support/ServerWebExchangeUtils.java

@@ -40,6 +40,7 @@
 import org.springframework.core.io.buffer.DataBufferUtils;
 import org.springframework.core.io.buffer.DefaultDataBuffer;
 import org.springframework.core.io.buffer.NettyDataBuffer;
+import org.springframework.core.io.buffer.PooledDataBuffer;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.server.reactive.AbstractServerHttpResponse;
 import org.springframework.http.server.reactive.ServerHttpRequest;
@@ -379,6 +380,27 @@ private static <T> Mono<T> cacheRequestBody(ServerWebExchange exchange, boolean
 			.flatMap(function);
 	}
 
+	/**
+	 * clear the request body in a ServerWebExchange attribute. The attribute is
+	 * {@link #CACHED_REQUEST_BODY_ATTR}.
+	 * @param exchange the available ServerWebExchange.
+	 */
+	public static void clearCachedRequestBody(ServerWebExchange exchange) {
+		Object attribute = exchange.getAttributes().remove(CACHED_REQUEST_BODY_ATTR);
+		if (attribute != null && attribute instanceof PooledDataBuffer) {
+			PooledDataBuffer dataBuffer = (PooledDataBuffer) attribute;
+			if (dataBuffer.isAllocated()) {
+				if (log.isTraceEnabled()) {
+					log.trace("releasing cached body in exchange attribute");
+				}
+				// ensure proper release
+				while (!dataBuffer.release()) {
+					// release() counts down until zero, will never be infinite loop
+				}
+			}
+		}
+	}
+
 	private static ServerHttpRequest decorate(ServerWebExchange exchange, DataBuffer dataBuffer,
 			boolean cacheDecoratedRequest) {
 		if (dataBuffer.readableByteCount() > 0) {