JsonLoggingEventLayout.java

package uk.co.appembassy.log4mqtt;

import org.apache.log4j.Layout;
import org.apache.log4j.spi.LoggingEvent;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Iterator;

/**
 * Created with IntelliJ IDEA.
 * User: rad
 * Date: 29/09/2012
 * Time: 14:17
 * To change this template use File | Settings | File Templates.
 */
public class JsonLoggingEventLayout extends Layout {

    private String hostname;
    private String ip;

    public void activateOptions() {
        try {
            hostname = InetAddress.getLocalHost().getHostName();
        } catch (UnknownHostException ex) {
            hostname = "<unknown>";
        }
        try {
            ip = InetAddress.getLocalHost().getHostAddress();
        } catch (UnknownHostException ex) {
            ip = "<unknown>";
        }
    }

    public boolean ignoresThrowable() { return true; }

    public String format(LoggingEvent event) {
        StringBuilder json = new StringBuilder();
        json.append("{");
        json.append("\"hostname\":");
        json.append("\"" + hostname + "\"");
        json.append(",\"ip\":");
        json.append("\"" + ip + "\"");
        json.append(",\"timestamp\":");
        json.append(event.getTimeStamp());
        json.append(",\"error_level_string\":");
        json.append("\"" + event.getLevel().toString() + "\"");
        json.append(",\"error_level_code\":");
        json.append(event.getLevel().toInt());
        json.append(",\"message\":");
        json.append("\"" + event.getMessage().toString().replaceAll("\"", "\\\\\"") + "\"");
        json.append(",\"fqn\":");
        json.append("\"" + event.getFQNOfLoggerClass().replaceAll("\"", "\\\\\"") + "\"");
        json.append(",\"logger_name\":");
        json.append("\"" + event.getLoggerName().replaceAll("\"", "\\\\\"") + "\"");
        if ( event.getNDC() != null ) {
            json.append(",\"ndc\":");
            json.append("\"" + event.getNDC().replaceAll("\"", "\\\\\"") + "\"");
        }
        if ( event.getRenderedMessage() != null ) {
            json.append(",\"rendered_message\":");
            json.append("\"" + event.getRenderedMessage().replaceAll("\"", "\\\\\"") + "\"");
        }
        if (event.locationInformationExists()) {
            json.append(",\"location_info\":");
            json.append("\"" + event.getLocationInformation().fullInfo.replaceAll("\"", "\\\\\"") + "\"");
        }
        if ( event.getThreadName() != null ) {
            json.append(",\"thread_name\":");
            json.append("\"" + event.getThreadName().replaceAll("\"", "\\\\\"") + "\"");
        }
        if ( event.getThrowableStrRep() != null ) {
            String[] throwable = event.getThrowableStrRep();
            if ( throwable.length > 0 ) {
                json.append(",\"throwable\":[");
                for ( int i=0; i<throwable.length; i++ ) {
                    if ( i > 0 ) json.append(",");
                    json.append("\"" + throwable[i].replaceAll("\"", "\\\\\"") + "\"");
                }
                json.append("\"]");
            }
        }

        if ( event.getProperties() != null && event.getProperties().size() > 0 ) {
            json.append(",\"properties\":{");
            Iterator<String> iter = event.getProperties().keySet().iterator();
            int c = 0;
            while (iter.hasNext()) {
                if ( c > 0 ) json.append(",");
                String key = iter.next();
                json.append("\"" + key.replaceAll("\"", "\\\\\"") + "\":");
                json.append("\"" + event.getProperty(key).replaceAll("\"", "\\\\\"") + "\"");
            }
            json.append("}");
        }

        json.append("}");
        return json.toString();
    }

}