Move interception code snippets to Java classes

This commit starts movint code snippets from the reference documentation
to actual Java classes so that they're compiled and checked at build
time.

spring-graphql-docs/src/main/java/org/springframework/graphql/docs/server/interception/web/Person.java

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2020-2022 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.graphql.docs.server.interception.web;
+
+public record Person(String firstName, String lastName) {
+}

spring-graphql-docs/src/main/java/org/springframework/graphql/docs/server/interception/web/RequestErrorInterceptor.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2020-2022 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.graphql.docs.server.interception.web;
+
+import java.util.List;
+
+import graphql.GraphQLError;
+import graphql.GraphqlErrorBuilder;
+import reactor.core.publisher.Mono;
+
+import org.springframework.graphql.server.WebGraphQlInterceptor;
+import org.springframework.graphql.server.WebGraphQlRequest;
+import org.springframework.graphql.server.WebGraphQlResponse;
+
+class RequestErrorInterceptor implements WebGraphQlInterceptor {
+
+	@Override
+	public Mono<WebGraphQlResponse> intercept(WebGraphQlRequest request, Chain chain) {
+		return chain.next(request).map(response -> {
+			if (response.isValid()) {
+				return response; // <1>
+			}
+
+			List<GraphQLError> errors = response.getErrors().stream() // <2>
+					.map(error -> {
+						GraphqlErrorBuilder<?> builder = GraphqlErrorBuilder.newError();
+						// ...
+						return builder.build();
+					})
+					.toList();
+
+			return response.transform(builder -> builder.errors(errors).build()); // <3>
+		});
+	}
+}

spring-graphql-docs/src/main/java/org/springframework/graphql/docs/server/interception/web/RequestHeaderInterceptor.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2020-2022 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.graphql.docs.server.interception.web;
+
+import java.util.Collections;
+
+import reactor.core.publisher.Mono;
+
+import org.springframework.graphql.data.method.annotation.ContextValue;
+import org.springframework.graphql.data.method.annotation.QueryMapping;
+import org.springframework.graphql.server.WebGraphQlInterceptor;
+import org.springframework.graphql.server.WebGraphQlRequest;
+import org.springframework.graphql.server.WebGraphQlResponse;
+import org.springframework.stereotype.Controller;
+
+class RequestHeaderInterceptor implements WebGraphQlInterceptor { // <1>
+
+	@Override
+	public Mono<WebGraphQlResponse> intercept(WebGraphQlRequest request, Chain chain) {
+		String value = request.getHeaders().getFirst("myHeader");
+		request.configureExecutionInput((executionInput, builder) ->
+				builder.graphQLContext(Collections.singletonMap("myHeader", value)).build());
+		return chain.next(request);
+	}
+}
+
+@Controller
+class MyContextValueController { // <2>
+
+	@QueryMapping
+	Person person(@ContextValue String myHeader) {
+		/**/ return new Person("spring", "graphql");
+	}
+}

spring-graphql-docs/src/main/java/org/springframework/graphql/docs/server/interception/web/ResponseHeaderInterceptor.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2020-2022 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.graphql.docs.server.interception.web;
+
+import graphql.GraphQLContext;
+import reactor.core.publisher.Mono;
+
+import org.springframework.graphql.data.method.annotation.QueryMapping;
+import org.springframework.graphql.server.WebGraphQlInterceptor;
+import org.springframework.graphql.server.WebGraphQlRequest;
+import org.springframework.graphql.server.WebGraphQlResponse;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.ResponseCookie;
+import org.springframework.stereotype.Controller;
+
+// Subsequent access from a WebGraphQlInterceptor
+
+class ResponseHeaderInterceptor implements WebGraphQlInterceptor {
+
+	@Override
+	public Mono<WebGraphQlResponse> intercept(WebGraphQlRequest request, Chain chain) { // <2>
+		return chain.next(request).doOnNext(response -> {
+			String value = response.getExecutionInput().getGraphQLContext().get("cookieName");
+			ResponseCookie cookie = ResponseCookie.from("cookieName", value).build();
+			response.getResponseHeaders().add(HttpHeaders.SET_COOKIE, cookie.toString());
+		});
+	}
+}
+
+@Controller
+class MyCookieController {
+
+	@QueryMapping
+	Person person(GraphQLContext context) { // <1>
+		context.put("cookieName", "123");
+		/**/ return new Person("spring", "graphql");
+	}
+}

spring-graphql-docs/src/main/java/org/springframework/graphql/docs/server/transports/rsocket/GraphQlRSocketController.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2020-2022 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.graphql.docs.server.transports.rsocket;
+
+import java.util.Map;
+
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import org.springframework.graphql.server.GraphQlRSocketHandler;
+import org.springframework.messaging.handler.annotation.MessageMapping;
+import org.springframework.stereotype.Controller;
+
+@Controller
+public class GraphQlRSocketController {
+
+	private final GraphQlRSocketHandler handler;
+
+	GraphQlRSocketController(GraphQlRSocketHandler handler) {
+		this.handler = handler;
+	}
+
+	@MessageMapping("graphql")
+	public Mono<Map<String, Object>> handle(Map<String, Object> payload) {
+		return this.handler.handle(payload);
+	}
+
+	@MessageMapping("graphql")
+	public Flux<Map<String, Object>> handleSubscription(Map<String, Object> payload) {
+		return this.handler.handleSubscription(payload);
+	}
+}