Java tutorial
/* * Copyright (C) 2015 Julien Bonjean <julien@bonjean.info> * * This program is free software; you can redistribute it and/or modify it under * the terms of the GNU General Public License as published by the Free Software * Foundation; either version 3 of the License, or (at your option) any later * version. * * This program is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more * details. * * You should have received a copy of the GNU General Public License along with * this program; if not, write to the Free Software Foundation, Inc., 51 * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ package info.bonjean.quinkana; import java.io.IOException; import java.io.InputStream; import java.net.Socket; import java.util.Iterator; import java.util.List; import java.util.Properties; import net.sourceforge.argparse4j.ArgumentParsers; import net.sourceforge.argparse4j.impl.Arguments; import net.sourceforge.argparse4j.inf.ArgumentParser; import net.sourceforge.argparse4j.inf.Namespace; import com.fasterxml.jackson.core.JsonFactory; import com.fasterxml.jackson.core.JsonParser; import com.fasterxml.jackson.core.JsonToken; import com.fasterxml.jackson.databind.JsonNode; import com.fasterxml.jackson.databind.ObjectMapper; /** * To keep it light, every error is fatal, and we don't use a logging library. * * @author Julien Bonjean <julien@bonjean.info> * */ public class Main { private enum Action { tail, list; } private static void run(String[] args) throws QuinkanaException { Properties properties = new Properties(); InputStream inputstream = Main.class.getResourceAsStream("/config.properties"); try { properties.load(inputstream); inputstream.close(); } catch (IOException e) { throw new QuinkanaException("cannot load internal properties", e); } String name = (String) properties.get("name"); String description = (String) properties.get("description"); String url = (String) properties.get("url"); String version = (String) properties.get("version"); String usage = (String) properties.get("help.usage"); String defaultHost = (String) properties.get("default.host"); int defaultPort = Integer.valueOf(properties.getProperty("default.port")); ArgumentParser parser = ArgumentParsers.newArgumentParser(name).description(description) .epilog("For more information, go to " + url).version("${prog} " + version).usage(usage); parser.addArgument("ACTION").type(Action.class).choices(Action.tail, Action.list).dest("action"); parser.addArgument("-H", "--host").setDefault(defaultHost) .help(String.format("logstash host (default: %s)", defaultHost)); parser.addArgument("-P", "--port").type(Integer.class).setDefault(defaultPort) .help(String.format("logstash TCP port (default: %d)", defaultPort)); parser.addArgument("-f", "--fields").nargs("+").help("fields to display"); parser.addArgument("-i", "--include").nargs("+").help("include filter (OR), example host=example.com") .metavar("FILTER").type(Filter.class); parser.addArgument("-x", "--exclude").nargs("+") .help("exclude filter (OR, applied after include), example: severity=debug").metavar("FILTER") .type(Filter.class); parser.addArgument("-s", "--single").action(Arguments.storeTrue()).help("display single result and exit"); parser.addArgument("--version").action(Arguments.version()).help("output version information and exit"); Namespace ns = parser.parseArgsOrFail(args); Action action = ns.get("action"); List<String> fields = ns.getList("fields"); List<Filter> includes = ns.getList("include"); List<Filter> excludes = ns.getList("exclude"); boolean single = ns.getBoolean("single"); String host = ns.getString("host"); int port = ns.getInt("port"); final Socket clientSocket; final InputStream is; try { clientSocket = new Socket(host, port); is = clientSocket.getInputStream(); } catch (IOException e) { throw new QuinkanaException("cannot connect to the server " + host + ":" + port, e); } // add a hook to ensure we clean the resources when leaving Runtime.getRuntime().addShutdownHook(new Thread() { @Override public void run() { try { is.close(); } catch (IOException e) { e.printStackTrace(); } try { clientSocket.close(); } catch (IOException e) { e.printStackTrace(); } } }); // prepare JSON parser ObjectMapper mapper = new ObjectMapper(); JsonFactory jsonFactory = mapper.getFactory(); JsonParser jp; try { jp = jsonFactory.createParser(is); } catch (IOException e) { throw new QuinkanaException("error during JSON parser creation", e); } JsonToken token; // action=list if (action.equals(Action.list)) { try { // do this in a separate loop to not pollute the main loop while ((token = jp.nextToken()) != null) { if (token != JsonToken.START_OBJECT) continue; // parse object JsonNode node = jp.readValueAsTree(); // print fields Iterator<String> fieldNames = node.fieldNames(); while (fieldNames.hasNext()) System.out.println(fieldNames.next()); System.exit(0); } } catch (IOException e) { throw new QuinkanaException("error during JSON parsing", e); } } // action=tail try { while ((token = jp.nextToken()) != null) { if (token != JsonToken.START_OBJECT) continue; // parse object JsonNode node = jp.readValueAsTree(); // filtering (includes) if (includes != null) { boolean skip = true; for (Filter include : includes) { if (include.match(node)) { skip = false; break; } } if (skip) continue; } // filtering (excludes) if (excludes != null) { boolean skip = false; for (Filter exclude : excludes) { if (exclude.match(node)) { skip = true; break; } } if (skip) continue; } // if no field specified, print raw output (JSON) if (fields == null) { System.out.println(node.toString()); if (single) break; continue; } // formatted output, build and print the string StringBuilder sb = new StringBuilder(128); for (String field : fields) { if (sb.length() > 0) sb.append(" "); if (node.get(field) != null && node.get(field).textValue() != null) sb.append(node.get(field).textValue()); } System.out.println(sb.toString()); if (single) break; } } catch (IOException e) { throw new QuinkanaException("error during JSON parsing", e); } } public static void main(String[] args) { try { run(args); } catch (QuinkanaException e) { System.err.println(e.getMessage()); System.exit(1); } } }