Java tutorial
package com.altoros.layout; import org.apache.log4j.Layout; import org.apache.log4j.spi.LoggingEvent; import org.apache.log4j.spi.ThrowableInformation; import org.json.JSONException; import org.json.JSONObject; import java.util.ArrayList; import java.util.List; /** Copyright (c) 2011 Stuart Clark, http://www.plant42.com/ Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. A Log4j layout that formats a LoggingEvent to a JSONified string. */ public class JSONLayout extends Layout { /** * format a given LoggingEvent to a string, in this case JSONified string * @param loggingEvent * @return String representation of LoggingEvent */ @Override public String format(LoggingEvent loggingEvent) { JSONObject root = new JSONObject(); try { //== write basic fields writeBasic(root, loggingEvent); //== write throwable fields writeThrowable(root, loggingEvent); } catch (JSONException e) { e.printStackTrace(); } return root.toString(); } /** * Converts LoggingEvent Throwable to JSON object * @param json * @param event * @throws JSONException */ protected void writeThrowable(JSONObject json, LoggingEvent event) throws JSONException { ThrowableInformation ti = event.getThrowableInformation(); if (ti != null) { Throwable t = ti.getThrowable(); JSONObject throwable = new JSONObject(); throwable.put("message", t.getMessage()); throwable.put("className", t.getClass().getCanonicalName()); List<JSONObject> traceObjects = new ArrayList<JSONObject>(); for (StackTraceElement ste : t.getStackTrace()) { JSONObject element = new JSONObject(); element.put("class", ste.getClassName()); element.put("method", ste.getMethodName()); element.put("line", ste.getLineNumber()); element.put("file", ste.getFileName()); traceObjects.add(element); } json.put("stackTrace", traceObjects); json.put("throwable", throwable); } } /** * Converts basic LogginEvent properties to JSON object * @param json * @param event * @throws JSONException */ protected void writeBasic(JSONObject json, LoggingEvent event) throws JSONException { json.put("threadName", event.getThreadName()); json.put("level", event.getLevel().toString()); json.put("timestamp", event.getTimeStamp()); json.put("message", event.getMessage()); json.put("logger", event.getLoggerName()); } /** * Declares that this layout does not ignore throwable if available * @return */ @Override public boolean ignoresThrowable() { return false; } /** * Just fulfilling the interface/abstract class requirements */ // @Override public void activateOptions() { } }