Adds support for hints in reading/modifying request/response bodies.

fixes gh-298

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/factory/rewrite/ModifyRequestBodyGatewayFilterFactory.java

@@ -17,6 +17,7 @@
 
 package org.springframework.cloud.gateway.filter.factory.rewrite;
 
+import java.util.Map;
 import java.util.Optional;
 
 import org.reactivestreams.Publisher;
@@ -58,7 +59,7 @@ public class ModifyRequestBodyGatewayFilterFactory
 
 			if (reader.isPresent()) {
 				Mono<Object> readMono = reader.get()
-						.readMono(inElementType, exchange.getRequest(), null)
+						.readMono(inElementType, exchange.getRequest(), config.getInHints())
 						.cast(Object.class);
 
 				return process(readMono, peek -> {
@@ -74,7 +75,7 @@ public class ModifyRequestBodyGatewayFilterFactory
 
 						HttpMessageWriterResponse fakeResponse = new HttpMessageWriterResponse(exchange.getResponse().bufferFactory());
 						writer.get().write(publisher, inElementType, mediaType,
-								fakeResponse, null);
+								fakeResponse, config.getOutHints());
 						ServerHttpRequestDecorator decorator = new ServerHttpRequestDecorator(
 								exchange.getRequest()) {
 							@Override
@@ -109,6 +110,8 @@ public class ModifyRequestBodyGatewayFilterFactory
 	public static class Config {
 		private Class inClass;
 		private Class outClass;
+		private Map<String, Object> inHints;
+		private Map<String, Object> outHints;
 
 		private RewriteFunction rewriteFunction;
 
@@ -130,6 +133,24 @@ public class ModifyRequestBodyGatewayFilterFactory
 			return this;
 		}
 
+		public Map<String, Object> getInHints() {
+			return inHints;
+		}
+
+		public Config setInHints(Map<String, Object> inHints) {
+			this.inHints = inHints;
+			return this;
+		}
+
+		public Map<String, Object> getOutHints() {
+			return outHints;
+		}
+
+		public Config setOutHints(Map<String, Object> outHints) {
+			this.outHints = outHints;
+			return this;
+		}
+
 		public RewriteFunction getRewriteFunction() {
 			return rewriteFunction;
 		}

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/factory/rewrite/ModifyResponseBodyGatewayFilterFactory.java

@@ -17,6 +17,7 @@
 
 package org.springframework.cloud.gateway.filter.factory.rewrite;
 
+import java.util.Map;
 import java.util.Optional;
 
 import org.reactivestreams.Publisher;
@@ -53,7 +54,6 @@ public class ModifyResponseBodyGatewayFilterFactory
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public GatewayFilter apply(Config config) {
 		return new ModifyResponseGatewayFilter(config);
 	}
@@ -66,6 +66,7 @@ public class ModifyResponseBodyGatewayFilterFactory
 		}
 
 		@Override
+		@SuppressWarnings("unchecked")
 		public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
 			ServerHttpResponseDecorator responseDecorator = new ServerHttpResponseDecorator(exchange.getResponse()) {
 				@Override
@@ -81,13 +82,14 @@ public class ModifyResponseBodyGatewayFilterFactory
 
 						ResponseAdapter responseAdapter = new ResponseAdapter(body, getDelegate().getHeaders());
 
-						Flux<?> modified = reader.get().read(inElementType, responseAdapter, null)
+						Flux<?> modified = reader.get().read(inElementType, responseAdapter, config.getInHints())
 								.cast(inElementType.resolve())
 								.flatMap(originalBody -> Flux.just(config.rewriteFunction.apply(exchange, originalBody)))
 								.cast(outElementType.resolve());
 
 						return getDelegate().writeWith(
-								writer.get().write((Publisher)modified, outElementType, null, getDelegate(), null)
+								writer.get().write((Publisher)modified, outElementType, null, getDelegate(),
+										config.getOutHints())
 						);
 
 					}
@@ -141,6 +143,8 @@ public class ModifyResponseBodyGatewayFilterFactory
 	public static class Config {
 		private Class inClass;
 		private Class outClass;
+		private Map<String, Object> inHints;
+		private Map<String, Object> outHints;
 
 		private RewriteFunction rewriteFunction;
 
@@ -162,6 +166,24 @@ public class ModifyResponseBodyGatewayFilterFactory
 			return this;
 		}
 
+		public Map<String, Object> getInHints() {
+			return inHints;
+		}
+
+		public Config setInHints(Map<String, Object> inHints) {
+			this.inHints = inHints;
+			return this;
+		}
+
+		public Map<String, Object> getOutHints() {
+			return outHints;
+		}
+
+		public Config setOutHints(Map<String, Object> outHints) {
+			this.outHints = outHints;
+			return this;
+		}
+
 		public RewriteFunction getRewriteFunction() {
 			return rewriteFunction;
 		}

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/handler/predicate/ReadBodyPredicateFactory.java

@@ -17,6 +17,7 @@
 
 package org.springframework.cloud.gateway.handler.predicate;
 
+import java.util.Map;
 import java.util.Optional;
 import java.util.function.Predicate;
 
@@ -53,9 +54,9 @@ public class ReadBodyPredicateFactory extends AbstractRoutePredicateFactory<Read
             ResolvableType elementType = ResolvableType.forClass(config.getInClass());
             Optional<HttpMessageReader<?>> reader = getHttpMessageReader(codecConfigurer, elementType, mediaType);
             boolean answer = false;
-if (reader.isPresent()) {
+            if (reader.isPresent()) {
                 Mono<Object> readMono = reader.get()
-                        .readMono(elementType, exchange.getRequest(), null)
+                        .readMono(elementType, exchange.getRequest(), config.getHints())
                         .cast(Object.class);
                 answer = process(readMono, peek -> {
                     Optional<HttpMessageWriter<?>> writer = getHttpMessageWriter(codecConfigurer, elementType, mediaType);
@@ -63,7 +64,7 @@ if (reader.isPresent()) {
                     if (writer.isPresent()) {
                         Publisher publisher = Mono.just(peek);
                         HttpMessageWriterResponse fakeResponse = new HttpMessageWriterResponse(exchange.getResponse().bufferFactory());
-                        writer.get().write(publisher, elementType, mediaType, fakeResponse, null);
+                        writer.get().write(publisher, elementType, mediaType, fakeResponse, config.getHints());
                         exchange.getAttributes().put(CACHED_REQUEST_BODY_KEY, fakeResponse.getBody());
                     }
                     return config.getPredicate().test(peek);
@@ -77,6 +78,7 @@ if (reader.isPresent()) {
     public static class Config {
         private Class inClass;
         private Predicate predicate;
+        private Map<String, Object> hints;
 
         public Class getInClass() {
             return inClass;
@@ -101,5 +103,14 @@ if (reader.isPresent()) {
             this.predicate = predicate;
             return this;
         }
-    }
+
+		public Map<String, Object> getHints() {
+			return hints;
+		}
+
+		public Config setHints(Map<String, Object> hints) {
+			this.hints = hints;
+			return this;
+		}
+	}
 }