Add SyncGraphQlTransport and Interceptor

See gh-771

spring-graphql/src/main/java/org/springframework/graphql/client/SyncGraphQlClientInterceptor.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2020-2024 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.client;
+
+/**
+ * Interceptor of {@link GraphQlClient} requests.
+ *
+ * @author Rossen Stoyanchev
+ * @since 1.3
+ */
+public interface SyncGraphQlClientInterceptor {
+
+	/**
+	 * Intercept a single response request (query and mutation operations), and
+	 * delegate to the rest of the chain including other interceptors followed
+	 * by the {@link GraphQlTransport}.
+	 * @param request the request to perform
+	 * @param chain the rest of the chain to perform the request
+	 * @return the response
+	 * @see GraphQlClient.RequestSpec#execute()
+	 */
+	default ClientGraphQlResponse intercept(ClientGraphQlRequest request, Chain chain) {
+		return chain.next(request);
+	}
+
+	/**
+	 * Return a new {@link SyncGraphQlClientInterceptor} that invokes the current
+	 * interceptor first and then the one that is passed in.
+	 * @param interceptor the interceptor to delegate to after "this"
+	 * @return the new interceptor instance
+	 */
+	default SyncGraphQlClientInterceptor andThen(SyncGraphQlClientInterceptor interceptor) {
+		return new SyncGraphQlClientInterceptor() {
+
+			@Override
+			public ClientGraphQlResponse intercept(ClientGraphQlRequest request, Chain chain) {
+				return SyncGraphQlClientInterceptor.this.intercept(
+						request, nextRequest -> interceptor.intercept(nextRequest, chain));
+			}
+		};
+	}
+
+
+	/**
+	 * Contract to delegate to the rest of the chain.
+	 */
+	interface Chain {
+
+		/**
+		 * Delegate to the rest of the chain to perform the request.
+		 * @param request the request to perform
+		 * @return the GraphQL response
+		 * @throws GraphQlTransportException in case of errors due to transport or
+		 * other issues related to encoding and decoding the request and response.
+		 */
+		ClientGraphQlResponse next(ClientGraphQlRequest request);
+
+	}
+
+}

spring-graphql/src/main/java/org/springframework/graphql/client/SyncGraphQlTransport.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2002-2024 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.client;
+
+import org.springframework.graphql.GraphQlRequest;
+import org.springframework.graphql.GraphQlResponse;
+
+
+/**
+ * Contract for blocking execution of GraphQL requests over some transport.
+ *
+ * @author Rossen Stoyanchev
+ * @since 1.3
+ */
+public interface SyncGraphQlTransport {
+
+	/**
+	 * Execute a request with a single response such as a "query" or "mutation".
+	 * @param request the request to execute
+	 * @return the {@code GraphQlResponse} for the response.
+	 * @throws GraphQlTransportException in case of errors due to transport or
+	 * other issues related to encoding and decoding the request and response.
+	 */
+	GraphQlResponse execute(GraphQlRequest request);
+
+}