Add GraphQlClient support for WebSocket

See gh-10

Author: rstoyanchev

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

@@ -0,0 +1,44 @@
+/*
+ * 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 java.util.List;
+
+import graphql.GraphQLError;
+
+/**
+ *
+ * @author Rossen Stoyanchev
+ * @since 1.0.0
+ */
+@SuppressWarnings("serial")
+public class SubscriptionErrorException extends RuntimeException {
+
+	private final List<GraphQLError> errors;
+
+
+	public SubscriptionErrorException(List<GraphQLError> errors) {
+		super("GraphQL subscription error: " + errors);
+		this.errors = errors;
+	}
+
+
+	public List<GraphQLError> getErrors() {
+		return this.errors;
+	}
+
+}

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

@@ -0,0 +1,94 @@
+/*
+ * 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.core.ResolvableType;
+import org.springframework.core.codec.Decoder;
+import org.springframework.core.codec.Encoder;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.DataBufferUtils;
+import org.springframework.graphql.web.webflux.GraphQlWebSocketMessage;
+import org.springframework.http.MediaType;
+import org.springframework.http.codec.ClientCodecConfigurer;
+import org.springframework.http.codec.CodecConfigurer;
+import org.springframework.http.codec.DecoderHttpMessageReader;
+import org.springframework.http.codec.EncoderHttpMessageWriter;
+import org.springframework.util.Assert;
+import org.springframework.util.MimeTypeUtils;
+import org.springframework.web.reactive.socket.WebSocketMessage;
+import org.springframework.web.reactive.socket.WebSocketSession;
+
+/**
+ * Delegate that can be embedded in a class to help with encoding and decoding
+ * GraphQL over WebSocket messages.
+ *
+ * @author Rossen Stoyanchev
+ * @since 1.0.0
+ */
+final class WebSocketCodecDelegate {
+
+	private static final ResolvableType MESSAGE_TYPE = ResolvableType.forClass(GraphQlWebSocketMessage.class);
+
+
+	private final Decoder<?> decoder;
+
+	private final Encoder<?> encoder;
+
+
+	WebSocketCodecDelegate() {
+		this(ClientCodecConfigurer.create());
+	}
+
+	WebSocketCodecDelegate(CodecConfigurer codecConfigurer) {
+		Assert.notNull(codecConfigurer, "CodecConfigurer is required");
+		this.decoder = initDecoder(codecConfigurer);
+		this.encoder = initEncoder(codecConfigurer);
+	}
+
+	private static Decoder<?> initDecoder(CodecConfigurer configurer) {
+		return configurer.getReaders().stream()
+				.filter((reader) -> reader.canRead(MESSAGE_TYPE, MediaType.APPLICATION_JSON))
+				.map((reader) -> ((DecoderHttpMessageReader<?>) reader).getDecoder())
+				.findFirst()
+				.orElseThrow(() -> new IllegalArgumentException("No JSON Decoder"));
+	}
+
+	private static Encoder<?> initEncoder(CodecConfigurer configurer) {
+		return configurer.getWriters().stream()
+				.filter((writer) -> writer.canWrite(MESSAGE_TYPE, MediaType.APPLICATION_JSON))
+				.map((writer) -> ((EncoderHttpMessageWriter<?>) writer).getEncoder())
+				.findFirst()
+				.orElseThrow(() -> new IllegalArgumentException("No JSON Encoder"));
+	}
+
+
+	@SuppressWarnings("unchecked")
+	public <T> WebSocketMessage encode(WebSocketSession session, GraphQlWebSocketMessage message) {
+
+		DataBuffer buffer = ((Encoder<T>) this.encoder).encodeValue(
+				(T) message, session.bufferFactory(), MESSAGE_TYPE, MimeTypeUtils.APPLICATION_JSON, null);
+
+		return new WebSocketMessage(WebSocketMessage.Type.TEXT, buffer);
+	}
+
+	@SuppressWarnings("ConstantConditions")
+	public GraphQlWebSocketMessage decode(WebSocketMessage webSocketMessage) {
+		DataBuffer buffer = DataBufferUtils.retain(webSocketMessage.getPayload());
+		return (GraphQlWebSocketMessage) this.decoder.decode(buffer, MESSAGE_TYPE, null, null);
+	}
+
+
+}