Java tutorial
/* * Copyright 2015 - 2018 Anton Tananaev (anton@traccar.org) * * 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 * * 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.traccar; import io.netty.buffer.ByteBuf; import io.netty.buffer.ByteBufUtil; import io.netty.channel.Channel; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.ChannelInboundHandlerAdapter; import io.netty.util.ReferenceCountUtil; import org.traccar.helper.DataConverter; import org.traccar.model.Position; import java.net.SocketAddress; import java.nio.charset.StandardCharsets; import java.util.Collection; public abstract class ExtendedObjectDecoder extends ChannelInboundHandlerAdapter { private void saveOriginal(Object decodedMessage, Object originalMessage) { if (Context.getConfig().getBoolean("database.saveOriginal") && decodedMessage instanceof Position) { Position position = (Position) decodedMessage; if (originalMessage instanceof ByteBuf) { ByteBuf buf = (ByteBuf) originalMessage; position.set(Position.KEY_ORIGINAL, ByteBufUtil.hexDump(buf)); } else if (originalMessage instanceof String) { position.set(Position.KEY_ORIGINAL, DataConverter.printHex(((String) originalMessage).getBytes(StandardCharsets.US_ASCII))); } } } @Override public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception { NetworkMessage networkMessage = (NetworkMessage) msg; Object originalMessage = networkMessage.getMessage(); try { Object decodedMessage = decode(ctx.channel(), networkMessage.getRemoteAddress(), originalMessage); onMessageEvent(ctx.channel(), networkMessage.getRemoteAddress(), originalMessage, decodedMessage); if (decodedMessage == null) { decodedMessage = handleEmptyMessage(ctx.channel(), networkMessage.getRemoteAddress(), originalMessage); } if (decodedMessage != null) { if (decodedMessage instanceof Collection) { for (Object o : (Collection) decodedMessage) { saveOriginal(o, originalMessage); ctx.fireChannelRead(o); } } else { saveOriginal(decodedMessage, originalMessage); ctx.fireChannelRead(decodedMessage); } } } finally { ReferenceCountUtil.release(originalMessage); } } protected void onMessageEvent(Channel channel, SocketAddress remoteAddress, Object originalMessage, Object decodedMessage) { } protected Object handleEmptyMessage(Channel channel, SocketAddress remoteAddress, Object msg) { return null; } protected abstract Object decode(Channel channel, SocketAddress remoteAddress, Object msg) throws Exception; }