Add transport specific GraphQlClient extensions

Add HttpGraphQlClient and WebSocketGraphQlClient extensions along with
a builder hierarchy that combines GraphQlClient and transport specific
configuration.

See gh-10

Author: rstoyanchev

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

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2002-2022 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.client;
+
+
+import org.springframework.util.Assert;
+
+/**
+ * Base class for extensions of {@link GraphQlClient} that mainly assist with
+ * building the underlying transport, but otherwise delegate to the default
+ * {@link GraphQlClient} implementation for actual request execution.
+ *
+ * <p>Subclasses must implement {@link GraphQlClient#mutate()} to allow mutation
+ * of both {@code GraphQlClient} and {@code GraphQlTransport} configuration.
+ *
+ * @author Rossen Stoyanchev
+ * @since 1.0.0
+ */
+public abstract class AbstractDelegatingGraphQlClient implements GraphQlClient {
+
+	private final GraphQlClient graphQlClient;
+
+
+	protected AbstractDelegatingGraphQlClient(GraphQlClient graphQlClient) {
+		Assert.notNull(graphQlClient, "GraphQlClient is required");
+		this.graphQlClient = graphQlClient;
+	}
+
+
+	public GraphQlClient.RequestSpec document(String document) {
+		return this.graphQlClient.document(document);
+	}
+
+	public GraphQlClient.RequestSpec documentName(String name) {
+		return this.graphQlClient.documentName(name);
+	}
+
+}

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

@@ -18,6 +18,7 @@
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.function.Consumer;
 
 import com.jayway.jsonpath.Configuration;
 import com.jayway.jsonpath.DocumentContext;
@@ -35,7 +36,11 @@
 import org.springframework.util.StringUtils;
 
 /**
- * Default implementation of {@link GraphQlClient}.
+ * Default {@link GraphQlClient} implementation with the logic to initialize
+ * requests and handle responses, and delegates to a {@link GraphQlTransport}
+ * for actual request execution.
+ *
+ * <p>This class is final but works with any transport.
  *
  * @author Rossen Stoyanchev
  * @since 1.0.0
@@ -48,9 +53,12 @@ final class DefaultGraphQlClient implements GraphQlClient {
 
 	private final DocumentSource documentSource;
 
+	private final Consumer<Builder<?>> builderInitializer;
+
 
 	DefaultGraphQlClient(
-			GraphQlTransport transport, Configuration jsonPathConfig, DocumentSource documentSource) {
+			GraphQlTransport transport, Configuration jsonPathConfig, DocumentSource documentSource,
+			Consumer<Builder<?>> builderInitializer) {
 
 		Assert.notNull(transport, "GraphQlTransport is required");
 		Assert.notNull(jsonPathConfig, "Configuration is required");
@@ -59,15 +67,10 @@ final class DefaultGraphQlClient implements GraphQlClient {
 		this.transport = transport;
 		this.jsonPathConfig = jsonPathConfig;
 		this.documentSource = documentSource;
+		this.builderInitializer = builderInitializer;
 	}
 
 
-	@SuppressWarnings("unchecked")
-	@Override
-	public <T extends GraphQlTransport> T getTransport(Class<T> requiredType) {
-		return (requiredType.isInstance(this.transport) ? (T) this.transport : null);
-	}
-
 	@Override
 	public RequestSpec document(String document) {
 		return new DefaultRequestSpec(Mono.just(document), this.transport, this.jsonPathConfig);
@@ -79,6 +82,13 @@ public RequestSpec documentName(String name) {
 		return new DefaultRequestSpec(document, this.transport, this.jsonPathConfig);
 	}
 
+	@Override
+	public Builder<?> mutate() {
+		DefaultGraphQlClientBuilder<?> builder = new DefaultGraphQlClientBuilder<>(this.transport);
+		this.builderInitializer.accept(builder);
+		return builder;
+	}
+
 
 	private static final class DefaultRequestSpec implements RequestSpec {
 
@@ -112,6 +122,12 @@ public DefaultRequestSpec variable(String name, Object value) {
 			return this;
 		}
 
+		@Override
+		public RequestSpec variables(Map<String, Object> variables) {
+			this.variables.putAll(variables);
+			return this;
+		}
+
 		@Override
 		public Mono<ResponseSpec> execute() {
 			return getRequestMono()
@@ -136,11 +152,14 @@ private Mono<GraphQlRequest> getRequestMono() {
 
 	private static class DefaultResponseSpec implements ResponseSpec {
 
+		private final ExecutionResult result;
+
 		private final DocumentContext jsonPathDocument;
 
 		private final List<GraphQLError> errors;
 
 		private DefaultResponseSpec(ExecutionResult result, Configuration jsonPathConfig) {
+			this.result = result;
 			this.jsonPathDocument = JsonPath.parse(result.toSpecification(), jsonPathConfig);
 			this.errors = result.getErrors();
 		}
@@ -180,6 +199,11 @@ public List<GraphQLError> errors() {
 			return this.errors;
 		}
 
+		@Override
+		public ExecutionResult andReturn() {
+			return this.result;
+		}
+
 	}
 
 }

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

@@ -13,25 +13,34 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.graphql.client;
 
+import java.util.function.Consumer;
+
 import com.jayway.jsonpath.Configuration;
 import com.jayway.jsonpath.spi.json.JacksonJsonProvider;
 import com.jayway.jsonpath.spi.mapper.JacksonMappingProvider;
 
+import org.springframework.graphql.support.CachingDocumentSource;
 import org.springframework.graphql.support.DocumentSource;
 import org.springframework.graphql.support.ResourceDocumentSource;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 
+
 /**
- * Default implementation of {@link GraphQlClient.Builder}.
+ * Default {@link GraphQlClient.Builder} implementation that builds a
+ * {@link GraphQlClient} for use with any transport.
+ *
+ * <p>Intended for use as a base class for builders that do assist with building
+ * the underlying transport. Such extension
  *
  * @author Rossen Stoyanchev
  * @since 1.0.0
  */
-class DefaultGraphQlClientBuilder implements GraphQlClient.Builder {
+public class DefaultGraphQlClientBuilder<B extends DefaultGraphQlClientBuilder<B>> implements GraphQlClient.Builder<B> {
 
 	private static final boolean jackson2Present;
 
@@ -42,53 +51,70 @@ class DefaultGraphQlClientBuilder implements GraphQlClient.Builder {
 	}
 
 
-	private final GraphQlTransport transport;
-
 	@Nullable
-	private Configuration jsonPathConfig;
+	private GraphQlTransport transport;
 
 	@Nullable
 	private DocumentSource documentSource;
 
-
+	/**
+	 * Constructor with a given transport instance.
+	 */
 	DefaultGraphQlClientBuilder(GraphQlTransport transport) {
 		Assert.notNull(transport, "GraphQlTransport is required");
 		this.transport = transport;
 	}
 
+	/**
+	 * Constructor for subclass builders that will call
+	 * {@link #transport(GraphQlTransport)} to set the transport instance
+	 * before {@link #build()}.
+	 */
+	DefaultGraphQlClientBuilder() {
+	}
 
-	@Override
-	public GraphQlClient.Builder jsonPathConfig(@Nullable Configuration config) {
-		this.jsonPathConfig = config;
-		return this;
+	protected void transport(GraphQlTransport transport) {
+		this.transport = transport;
 	}
 
 	@Override
-	public GraphQlClient.Builder documentSource(@Nullable DocumentSource contentLoader) {
+	public B documentSource(@Nullable DocumentSource contentLoader) {
 		this.documentSource = contentLoader;
-		return this;
+		return self();
+	}
+
+	@SuppressWarnings("unchecked")
+	private <T extends B> T self() {
+		return (T) this;
 	}
 
 	@Override
 	public GraphQlClient build() {
-		return new DefaultGraphQlClient(this.transport, initJsonPathConfig(), initRequestNameResolver());
+		Assert.notNull(this.transport, "No GraphQlTransport. Has a subclass not initialized it?");
+		return new DefaultGraphQlClient(this.transport, initJsonPathConfig(), initDocumentSource(), getBuilderInitializer());
 	}
 
 	private Configuration initJsonPathConfig() {
-		if (this.jsonPathConfig != null) {
-			return this.jsonPathConfig;
-		}
-		else if (jackson2Present) {
-			return Jackson2Configuration.create();
-		}
-		else {
-			return Configuration.builder().build();
-		}
+		// Allow configuring JSONPath with codecs from transport subclasses
+		return (jackson2Present ? Jackson2Configuration.create() : Configuration.builder().build());
 	}
 
-	private DocumentSource initRequestNameResolver() {
+	private DocumentSource initDocumentSource() {
 		return (this.documentSource == null ?
-				new ResourceDocumentSource() : this.documentSource);
+				new CachingDocumentSource(new ResourceDocumentSource()) : this.documentSource);
+	}
+
+	/**
+	 * Exposes a {@code Consumer} to subclasses to initialize new builder instances
+	 * from the configuration of "this" builder.
+	 */
+	protected Consumer<GraphQlClient.Builder<?>> getBuilderInitializer() {
+		return builder -> {
+			if (this.documentSource != null) {
+				builder.documentSource(documentSource);
+			}
+		};
+
 	}