log4j2-JSONLayout/JSONLayout.java at master · gb96/log4j2-JSONLayout · GitHub

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/**
 * Default package
 */
importjava.io.IOException;
importjava.io.PrintWriter;
importjava.io.StringWriter;
importjava.nio.charset.Charset;
importjava.util.List;
importjava.util.Map;
importjava.util.Set;
importjava.util.TreeSet;

importorg.apache.commons.lang.StringUtils;
importorg.apache.logging.log4j.ThreadContext.ContextStack;
importorg.apache.logging.log4j.core.LogEvent;
importorg.apache.logging.log4j.core.config.plugins.Plugin;
importorg.apache.logging.log4j.core.config.plugins.PluginAttr;
importorg.apache.logging.log4j.core.config.plugins.PluginFactory;
importorg.apache.logging.log4j.core.layout.AbstractStringLayout;
importorg.apache.logging.log4j.message.MapMessage;
importorg.apache.logging.log4j.message.Message;
importorg.codehaus.jackson.JsonFactory;
importorg.codehaus.jackson.JsonGenerator;

/**
 * Log4j 2.x layout for logging events as JSON.
 *
 * Based on
 * <a href="https://github.com/Aconex/json-log4j-layout">Aconex/json-log4j-layout</a>
 * <br/>
 * which also inspired <a href="https://github.com/carrot-garden/carrot-log">carrot-garden/carrot-log</a>
 *
 *
 * @author bowering
 */
@Plugin(name = "JSONLayout", type = "Core", elementType = "layout", printObject = true)
publicclassJSONLayoutextendsAbstractStringLayout {

publicstaticfinalCharsetUTF8 = Charset.forName("UTF-8");

privatefinalJsonFactoryjsonFactory = newJsonFactory();

/**
 * Constructor
 *
 * @param charset
 */
protectedJSONLayout(finalCharsetcharset) {
super(charset);
	}

/*
 * @see
 * org.apache.logging.log4j.core.Layout#toSerializable(org.apache.logging.
 * log4j.core.LogEvent)
 */
@Override
publicStringtoSerializable(finalLogEventevent) {
try {
finalStringWriterstringWriter = newStringWriter();
finalJsonGeneratorg = jsonFactory.createJsonGenerator(stringWriter);
g.writeStartObject();
writeBasicFields(event, g);
writeMessageField(event, g);
writeMDC(event, g);
writeNDC(event, g);
writeThrowableEvents(event, g);
g.writeEndObject();
g.close();
stringWriter.append("\n");
returnstringWriter.toString();
 } catch (IOExceptione) {
LOGGER.error("Could not write event as JSON", e);
 }
returnStringUtils.EMPTY;
	}


privatestaticvoidwriteBasicFields(finalLogEventevent, finalJsonGeneratorg)
throwsIOException {
g.writeStringField("logger", event.getLoggerName());
g.writeStringField("level", event.getLevel().toString());
g.writeNumberField("timestamp", event.getMillis());
g.writeStringField("threadName", event.getThreadName());
	}

privatestaticvoidwriteMessageField(finalLogEventevent,
finalJsonGeneratorg) throwsIOException {

finalMessagemessage = event.getMessage();
if (message == null) return;

if (messageinstanceofMapMessage) {
finalMapMessagemapMessage = (MapMessage) message;
finalMap<String, String> map = mapMessage.getData();
writeStringMap("msg", map, g);
 } else {
g.writeStringField("msg", message.toString());
 }
	}

privatestaticvoidwriteMDC(finalLogEventevent, finalJsonGeneratorg) throwsIOException {
writeStringMap("mdc", event.getContextMap(), g);
	}

privatestaticvoidwriteNDC(finalLogEventevent, finalJsonGeneratorg) throwsIOException {
finalContextStackndc = event.getContextStack();
if (ndc == null || ndc.getDepth() == 0) return;

finalList<String> ndcList = ndc.asList();
g.writeArrayFieldStart("ndc");
for (finalStringstackElement : ndcList) {
g.writeString(stackElement);
 }
g.writeEndArray();
	}


/**
 * Write the given stringMap as a JSON object with the given mapName
 *
 * @param mapName
 * @param stringMap
 * @param g
 * @throws IOException
 */
privatestaticvoidwriteStringMap(finalStringmapName, finalMap<String, String> stringMap, finalJsonGeneratorg) throwsIOException {
if (stringMap == null || stringMap.isEmpty()) return;
g.writeFieldName(mapName);
g.writeStartObject();

// TreeSet orders fields alphabetically by key:
finalSet<String> keys = newTreeSet<String>(stringMap.keySet());
for (finalStringkey : keys) {
g.writeStringField(key, stringMap.get(key));
 }

g.writeEndObject();
	}

privatestaticvoidwriteThrowableEvents(finalLogEventevent,
finalJsonGeneratorg) throwsIOException {
finalThrowablethrown = event.getThrown();
if (thrown == null)
return;

StringWritersw = newStringWriter();
PrintWriterpw = newPrintWriter(sw);
thrown.printStackTrace(pw);

StringthrowableString = sw.toString();
if (throwableString.isEmpty())
return;

g.writeStringField("throwable", throwableString);
	}

@PluginFactory
publicstaticJSONLayoutcreateLayout(
@PluginAttr("charset") finalStringcharset) {
Charsetc = UTF8;
if (charset != null) {
if (Charset.isSupported(charset)) {
c = Charset.forName(charset);
 } else {
LOGGER.error("Charset " + charset
 + " is not supported for layout, using " + c.displayName());
 }
 }
returnnewJSONLayout(c);
	}

}