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 de.hofuniversity.iisys.neo4j.websock.query.encoding.safe; import java.nio.ByteBuffer; import java.util.Arrays; import java.util.LinkedList; import java.util.List; import java.util.logging.Level; import java.util.logging.Logger; import java.util.zip.Deflater; import java.util.zip.Inflater; import javax.websocket.DecodeException; import javax.websocket.Decoder; import javax.websocket.EncodeException; import javax.websocket.Encoder; import javax.websocket.EndpointConfig; import org.json.JSONException; import org.json.JSONObject; import de.hofuniversity.iisys.neo4j.websock.query.WebsockQuery; import de.hofuniversity.iisys.neo4j.websock.session.WebsockConstants; import de.hofuniversity.iisys.neo4j.websock.util.JsonConverter; /** * Query handler implementation encoding and decoding WebsockQueries as JSON. * When decoding, uses the JSON map and list wrapper classes. * Ideally, maps and lists in queries to be encoded are already JSON objects * in wrappers. */ public class TSafeDeflateJsonQueryHandler implements Encoder.Binary<WebsockQuery>, Decoder.Binary<WebsockQuery> { private static final int DEFAULT_COMPRESSION_LEVEL = Deflater.BEST_SPEED; private static final int BUFFER_SIZE = 1024; private final Logger fLogger; private final boolean fDebug; private final int fCompression; private long fTotalBytesIn, fTotalBytesOut; public TSafeDeflateJsonQueryHandler() { fLogger = Logger.getLogger(this.getClass().getName()); fDebug = (fLogger.getLevel() == Level.FINEST); fCompression = DEFAULT_COMPRESSION_LEVEL; } public TSafeDeflateJsonQueryHandler(final String compression) { fLogger = Logger.getLogger(this.getClass().getName()); fDebug = (fLogger.getLevel() == Level.FINEST); int tmpComp = DEFAULT_COMPRESSION_LEVEL; if (WebsockConstants.FASTEST_COMPRESSION.equals(compression)) { tmpComp = Deflater.BEST_SPEED; } else if (WebsockConstants.BEST_COMPRESSION.equals(compression)) { tmpComp = Deflater.BEST_COMPRESSION; } else { fLogger.log(Level.WARNING, "unknown compression level '" + compression + "'; using default."); } fCompression = tmpComp; } @Override public void destroy() { } @Override public void init(EndpointConfig arg0) { } private ByteBuffer fuse(List<byte[]> buffers, final int length) { //fuses the buffers into a single array of the target length final ByteBuffer bb = ByteBuffer.allocate(length); for (byte[] buffer : buffers) { if (buffer.length > length - bb.position()) { bb.put(buffer, 0, length - bb.position()); } else { bb.put(buffer); } } //important bb.flip(); return bb; } @Override public ByteBuffer encode(final WebsockQuery query) throws EncodeException { ByteBuffer result = null; try { final JSONObject obj = JsonConverter.toJson(query); byte[] data = obj.toString().getBytes(); //compress final Deflater deflater = new Deflater(fCompression, true); deflater.setInput(data); int read = 0; int totalSize = 0; final List<byte[]> buffers = new LinkedList<byte[]>(); final byte[] buffer = new byte[BUFFER_SIZE]; read = deflater.deflate(buffer, 0, BUFFER_SIZE, Deflater.SYNC_FLUSH); while (read > 0) { totalSize += read; buffers.add(Arrays.copyOf(buffer, read)); read = deflater.deflate(buffer, 0, BUFFER_SIZE, Deflater.SYNC_FLUSH); } result = fuse(buffers, totalSize); if (fDebug) { fTotalBytesOut += totalSize; fLogger.log(Level.FINEST, "encoded compressed JSON message: " + totalSize + " bytes\n" + "total bytes sent: " + fTotalBytesOut); } } catch (JSONException e) { e.printStackTrace(); throw new EncodeException(query, "failed to encode JSON", e); } return result; } @Override public WebsockQuery decode(ByteBuffer buff) throws DecodeException { WebsockQuery query = null; try { //decompress final byte[] incoming = buff.array(); final Inflater inflater = new Inflater(true); inflater.setInput(incoming); int read = 0; int totalSize = 0; final List<byte[]> buffers = new LinkedList<byte[]>(); final byte[] buffer = new byte[BUFFER_SIZE]; read = inflater.inflate(buffer); while (read > 0) { totalSize += read; buffers.add(Arrays.copyOf(buffer, read)); read = inflater.inflate(buffer); } final byte[] data = fuse(buffers, totalSize).array(); final JSONObject obj = new JSONObject(new String(data)); if (fDebug) { fTotalBytesIn += incoming.length; fLogger.log(Level.FINEST, "received compressed JSON message: " + incoming.length + " bytes\n" + "total bytes received: " + fTotalBytesIn); } query = JsonConverter.fromJson(obj); } catch (Exception e) { e.printStackTrace(); throw new DecodeException(buff, "failed to decode JSON", e); } return query; } @Override public boolean willDecode(ByteBuffer buff) { boolean valid = true; //TODO: actually check whether it's a query try { //decompress final Inflater inflater = new Inflater(true); inflater.setInput(buff.array()); int read = 0; int totalSize = 0; final List<byte[]> buffers = new LinkedList<byte[]>(); byte[] buffer = new byte[BUFFER_SIZE]; read = inflater.inflate(buffer); while (read > 0) { totalSize += read; buffers.add(buffer); buffer = new byte[BUFFER_SIZE]; read = inflater.inflate(buffer); } final byte[] data = fuse(buffers, totalSize).array(); new JSONObject(new String(data)); } catch (Exception e) { valid = false; } return valid; } }