Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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 * * http://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.apache.tinkerpop.gremlin.server.handler; import org.apache.tinkerpop.gremlin.driver.MessageSerializer; import org.apache.tinkerpop.gremlin.driver.message.RequestMessage; import org.apache.tinkerpop.gremlin.driver.ser.SerializationException; import org.apache.tinkerpop.gremlin.driver.ser.Serializers; import io.netty.buffer.ByteBuf; import io.netty.channel.ChannelHandler; import io.netty.channel.ChannelHandlerContext; import io.netty.handler.codec.MessageToMessageDecoder; import io.netty.handler.codec.http.websocketx.BinaryWebSocketFrame; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.nio.charset.Charset; import java.util.List; import java.util.Map; /** * Decodes the contents of a {@code BinaryWebSocketFrame}. Binary-based frames assume that the format is encoded * in the first initial bytes of the message. From there the proper serializer can be chosen and the message * can then be deserialized. * * @author Stephen Mallette (http://stephen.genoprime.com) */ @ChannelHandler.Sharable public class WsGremlinBinaryRequestDecoder extends MessageToMessageDecoder<BinaryWebSocketFrame> { private static final Logger logger = LoggerFactory.getLogger(WsGremlinBinaryRequestDecoder.class); private static final Charset UTF8 = Charset.forName("UTF-8"); private final Map<String, MessageSerializer> serializers; public WsGremlinBinaryRequestDecoder(final Map<String, MessageSerializer> serializers) { this.serializers = serializers; } @Override protected void decode(final ChannelHandlerContext channelHandlerContext, final BinaryWebSocketFrame frame, final List<Object> objects) throws Exception { final ByteBuf messageBytes = frame.content(); final byte len = messageBytes.readByte(); if (len <= 0) { objects.add(RequestMessage.INVALID); return; } final ByteBuf contentTypeBytes = channelHandlerContext.alloc().buffer(len); try { messageBytes.readBytes(contentTypeBytes); final String contentType = contentTypeBytes.toString(UTF8); final MessageSerializer serializer = select(contentType, Serializers.DEFAULT_REQUEST_SERIALIZER); // it's important to re-initialize these channel attributes as they apply globally to the channel. in // other words, the next request to this channel might not come with the same configuration and mixed // state can carry through from one request to the next channelHandlerContext.channel().attr(StateKey.SESSION).set(null); channelHandlerContext.channel().attr(StateKey.SERIALIZER).set(serializer); channelHandlerContext.channel().attr(StateKey.USE_BINARY).set(true); try { objects.add(serializer.deserializeRequest(messageBytes.discardReadBytes())); } catch (SerializationException se) { objects.add(RequestMessage.INVALID); } } finally { contentTypeBytes.release(); } } private MessageSerializer select(final String mimeType, final MessageSerializer defaultSerializer) { if (logger.isWarnEnabled() && !serializers.containsKey(mimeType)) logger.warn( "Gremlin Server is not configured with a serializer for the requested mime type [{}] - using {} by default", mimeType, defaultSerializer.getClass().getName()); return serializers.getOrDefault(mimeType, defaultSerializer); } }