Introduce RouterFunction attributes

This commit introduces support for router function attributes, a
way to associate meta-data with a route.

Closes: gh-25938

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/AttributesTestVisitor.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2002-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.reactive.function.server;
+
+import java.util.Map;
+import java.util.function.Function;
+
+import reactor.core.publisher.Mono;
+
+import org.springframework.core.io.Resource;
+import org.springframework.lang.Nullable;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.entry;
+
+/**
+ * @author Arjen Poutsma
+ */
+class AttributesTestVisitor implements RouterFunctions.Visitor {
+
+	@Nullable
+	private Map<String, Object> attributes;
+
+	private int visitCount;
+
+	public int visitCount() {
+		return this.visitCount;
+	}
+
+	@Override
+	public void startNested(RequestPredicate predicate) {
+	}
+
+	@Override
+	public void endNested(RequestPredicate predicate) {
+	}
+
+	@Override
+	public void route(RequestPredicate predicate, HandlerFunction<?> handlerFunction) {
+		assertThat(this.attributes).isNotNull();
+		this.attributes = null;
+	}
+
+	@Override
+	public void resources(Function<ServerRequest, Mono<Resource>> lookupFunction) {
+	}
+
+	@Override
+	public void attributes(Map<String, Object> attributes) {
+		assertThat(attributes).containsExactly(entry("foo", "bar"), entry("baz", "qux"));
+		this.attributes = attributes;
+		this.visitCount++;
+	}
+
+	@Override
+	public void unknown(RouterFunction<?> routerFunction) {
+
+	}
+}

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/CustomRouteBuilder.java

@@ -0,0 +1,157 @@
+/*
+ * Copyright 2002-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.reactive.function.server;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+import reactor.core.publisher.Mono;
+
+import org.springframework.core.io.Resource;
+import org.springframework.lang.Nullable;
+
+/**
+ * @author Arjen Poutsma
+ */
+public class CustomRouteBuilder {
+
+	public static final String OPERATION_ATTRIBUTE = CustomRouteBuilder.class.getName() + ".operation";
+
+	private final RouterFunctions.Builder delegate = RouterFunctions.route();
+
+
+	private CustomRouteBuilder() {
+	}
+
+	public static CustomRouteBuilder route() {
+		return new CustomRouteBuilder();
+	}
+
+	public CustomRouteBuilder GET(String pattern, HandlerFunction<ServerResponse> handlerFunction,
+			Consumer<OperationBuilder> operationsConsumer) {
+
+		OperationBuilder builder = new OperationBuilder();
+		operationsConsumer.accept(builder);
+
+		this.delegate.GET(pattern, handlerFunction)
+				.withAttribute(OPERATION_ATTRIBUTE, builder.operation);
+
+		return this;
+	}
+
+	public RouterFunction<ServerResponse> build() {
+		return this.delegate.build();
+	}
+
+	public static void main(String[] args) {
+		RouterFunction<ServerResponse> routerFunction =
+				route()
+						.GET("/foo", request -> ServerResponse.ok().build(), ops -> ops
+								.parameter("key1", "My key1 description")
+								.parameter("key1", "My key1 description")
+								.response(200, "This is normal response description")
+								.response(404, "This is response description")
+						)
+						.build();
+
+		AttributesVisitor visitor = new AttributesVisitor();
+		routerFunction.accept(visitor);
+	}
+
+
+	public static class OperationBuilder {
+
+		private final Operation operation = new Operation();
+
+		public OperationBuilder parameter(String name, String description) {
+			this.operation.parameter(name, description);
+			return this;
+		}
+
+		public OperationBuilder response(int statusCode, String description) {
+			this.operation.response(statusCode, description);
+			return this;
+		}
+
+	}
+
+
+	static class Operation {
+
+		private final Map<String, String> parameters = new LinkedHashMap<>();
+
+		private final Map<Integer, String > responses = new LinkedHashMap<>();
+
+		public void parameter(String name, String description) {
+			this.parameters.put(name, description);
+		}
+
+		public void response(int status, String description) {
+			this.responses.put(status, description);
+		}
+
+		@Override
+		public String toString() {
+			return "parameters=" + parameters +
+					", responses=" + responses;
+		}
+	}
+
+	static class AttributesVisitor implements RouterFunctions.Visitor {
+
+		@Nullable
+		private Map<String, Object> attributes;
+
+		@Override
+		public void attributes(Map<String, Object> attributes) {
+			this.attributes = attributes;
+		}
+
+		@Override
+		public void route(RequestPredicate predicate, HandlerFunction<?> handlerFunction) {
+			System.out.printf("Route predicate %s->%s%nhas attributes %s", predicate, handlerFunction, this.attributes);
+			this.attributes = null;
+		}
+
+		@Override
+		public void startNested(RequestPredicate predicate) {
+			// TODO
+		}
+
+		@Override
+		public void endNested(RequestPredicate predicate) {
+			// TODO
+
+		}
+
+		@Override
+		public void resources(Function<ServerRequest, Mono<Resource>> lookupFunction) {
+			// TODO
+
+		}
+
+		@Override
+		public void unknown(RouterFunction<?> routerFunction) {
+			// TODO
+
+		}
+	}
+
+
+}

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/RouterFunctionBuilderTests.java

@@ -232,5 +232,23 @@ public class RouterFunctionBuilderTests {
 
 	}
 
+	@Test
+	public void attributes() {
+		RouterFunction<ServerResponse> route = RouterFunctions.route()
+				.GET("/atts/1", request -> ServerResponse.ok().build())
+				.withAttribute("foo", "bar")
+				.withAttribute("baz", "qux")
+				.GET("/atts/2", request -> ServerResponse.ok().build())
+				.withAttributes(atts -> {
+					atts.put("foo", "bar");
+					atts.put("baz", "qux");
+				})
+				.build();
+
+		AttributesTestVisitor visitor = new AttributesTestVisitor();
+		route.accept(visitor);
+		assertThat(visitor.visitCount()).isEqualTo(2);
+	}
+
 
 }

spring-webflux/src/test/java/org/springframework/web/reactive/function/server/RouterFunctionTests.java

@@ -26,6 +26,7 @@ import org.springframework.web.testfixture.http.server.reactive.MockServerHttpRe
 import org.springframework.web.testfixture.server.MockServerWebExchange;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.web.reactive.function.server.RequestPredicates.GET;
 
 /**
  * @author Arjen Poutsma
@@ -126,9 +127,29 @@ public class RouterFunctionTests {
 				.verify();
 	}
 
+	@Test
+	public void attributes() {
+		RouterFunction<ServerResponse> route = RouterFunctions.route(
+				GET("/atts/1"), request -> ServerResponse.ok().build())
+				.withAttribute("foo", "bar")
+				.withAttribute("baz", "qux")
+				.and(RouterFunctions.route(GET("/atts/2"), request -> ServerResponse.ok().build())
+				.withAttributes(atts -> {
+					atts.put("foo", "bar");
+					atts.put("baz", "qux");
+				}));
+
+		AttributesTestVisitor visitor = new AttributesTestVisitor();
+		route.accept(visitor);
+		assertThat(visitor.visitCount()).isEqualTo(2);
+	}
+
+
 
 	private Mono<ServerResponse> handlerMethod(ServerRequest request) {
 		return ServerResponse.ok().bodyValue("42");
 	}
 
+
+
 }