Java tutorial
/* * Copyright 2019 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.protocol; import com.fasterxml.jackson.databind.util.ByteBufferBackedInputStream; import io.netty.buffer.ByteBuf; import io.netty.buffer.Unpooled; import io.netty.channel.Channel; import io.netty.handler.codec.http.FullHttpRequest; import io.netty.handler.codec.http.HttpResponseStatus; import org.traccar.BaseHttpProtocolDecoder; import org.traccar.DeviceSession; import org.traccar.Protocol; import org.traccar.helper.DataConverter; import org.traccar.model.Position; import org.w3c.dom.Document; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException; import javax.xml.xpath.XPath; import javax.xml.xpath.XPathConstants; import javax.xml.xpath.XPathExpression; import javax.xml.xpath.XPathExpressionException; import javax.xml.xpath.XPathFactory; import java.net.SocketAddress; import java.util.Date; import java.util.LinkedList; import java.util.List; public class GlobalstarProtocolDecoder extends BaseHttpProtocolDecoder { private DocumentBuilder documentBuilder; private XPath xPath; private XPathExpression messageExpression; public GlobalstarProtocolDecoder(Protocol protocol) { super(protocol); try { DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance(); builderFactory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true); builderFactory.setFeature("http://xml.org/sax/features/external-general-entities", false); builderFactory.setFeature("http://xml.org/sax/features/external-parameter-entities", false); builderFactory.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false); builderFactory.setXIncludeAware(false); builderFactory.setExpandEntityReferences(false); documentBuilder = builderFactory.newDocumentBuilder(); xPath = XPathFactory.newInstance().newXPath(); messageExpression = xPath.compile("//stuMessages/stuMessage"); } catch (ParserConfigurationException | XPathExpressionException e) { throw new RuntimeException(e); } } @Override protected Object decode(Channel channel, SocketAddress remoteAddress, Object msg) throws Exception { FullHttpRequest request = (FullHttpRequest) msg; Document document = documentBuilder.parse(new ByteBufferBackedInputStream(request.content().nioBuffer())); NodeList nodes = (NodeList) messageExpression.evaluate(document, XPathConstants.NODESET); List<Position> positions = new LinkedList<>(); for (int i = 0; i < nodes.getLength(); i++) { Node node = nodes.item(i); DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, xPath.evaluate("esn", node)); if (deviceSession != null) { Position position = new Position(getProtocolName()); position.setDeviceId(deviceSession.getDeviceId()); position.setValid(true); position.setTime(new Date(Long.parseLong(xPath.evaluate("unixTime", node)) * 1000)); ByteBuf buf = Unpooled .wrappedBuffer(DataConverter.parseHex(xPath.evaluate("payload", node).substring(2))); buf.readUnsignedByte(); // flags position.setLatitude(buf.readUnsignedMedium() * 90.0 / (1 << 23)); if (position.getLatitude() > 90) { position.setLatitude(position.getLatitude() - 180); } position.setLongitude(buf.readUnsignedMedium() * 90.0 / (1 << 23)); if (position.getLongitude() > 180) { position.setLongitude(position.getLongitude() - 360); } buf.readUnsignedByte(); // status buf.readUnsignedByte(); // status positions.add(position); } } sendResponse(channel, HttpResponseStatus.OK); return positions; } }