com.couragelabs.logging.GlobalContextSocketAppender.java Source code

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Here is the source code for com.couragelabs.logging.GlobalContextSocketAppender.java

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/*
 * 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, see <http://www.gnu.org/licenses/>.
 */
package com.couragelabs.logging;

import org.apache.log4j.Logger;
import org.apache.log4j.net.SocketAppender;
import org.apache.log4j.spi.LoggingEvent;
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import static java.lang.String.format;

/**
 * The GlobalContextSocketAppender only exists to ensure a global context is
 * provided to remote servers, regardless of the thread a log message may
 * have come from. This works around the inherent limitations in the
 * Mapped Diagnostic Context in Log4J.
 * <p>
 * Simply configure this appender with a GlobalContext which can be simple
 * JSON. The following formats are accepted:
 * </p>
 * <code>
 * # Generates a field in the MDC called "global" with the value "hello"<br>
 * log4j.appender.socket.GlobalContext="hello"<br><br>
 *
 * # Generates two fields in the MDC called "global0" and "global1", <br>
 * # each with values "hello" and "world," respectively.<br>
 * log4j.appender.socket.GlobalContext=["hello", "world"]<br><br>
 *
 * # Generates two fields in the MDS called "thing" and "bits", <br>
 * # each with values "stuff" and "junk," respectively.<br>
 * log4j.appender.socket.GlobalContext={"thing":"stuff", "bits":"junk"}
 * </code>
 */
public class GlobalContextSocketAppender extends SocketAppender {
    private Map<String, String> globalContext;

    /**
     * Update the given event with the global context then send it to the
     * superclass for sending to the remote server.
     * @param event Event to append.
     */
    @Override
    @SuppressWarnings("unchecked")
    public void append(LoggingEvent event) {
        Map<String, String> contextMap = getGlobalContextAsMap();

        for (String key : contextMap.keySet()) {
            String value = contextMap.get(key);
            event.setProperty(key, value);
        }
        super.append(event);
    }

    /**
     * Retrieve a clean map of global context to append to each logging event.
     * @return A map of global context key/value pairs.
     */
    public Map<String, String> getGlobalContextAsMap() {
        if (globalContext == null) {
            globalContext = new HashMap<>();
            System.out.println("Warning: No globalContext specified.");
        }
        return globalContext;
    }

    /**
     * If you call setGlobalContext with "test" you will receive
     * {"global":"test"} out of this method. Overly clever? I think not! ;-)
     *
     * @return The fully processed global context property, serialized as JSON.
     */
    @SuppressWarnings("unchecked")
    public String getGlobalContext() {
        if (globalContext != null) {
            JSONObject o = new JSONObject();
            o.putAll(globalContext);
            String globalContextStr = o.toJSONString();
            System.out.println(globalContextStr);
            return globalContextStr;
        }
        return null;
    }

    /**
     * @param globalContext Global context to set.
     * @throws ParseException If parsing the global context fails.
     */
    public void setGlobalContext(String globalContext) throws ParseException {
        if (globalContext != null) {
            this.globalContext = new HashMap<>();
            JSONParser parser = new JSONParser();
            Object parsed = parser.parse(globalContext);
            if (parsed instanceof String) {
                this.globalContext.put("global", (String) parsed);
            } else if (parsed instanceof JSONArray) {
                Iterator iterator = ((JSONArray) parsed).iterator();
                int i = 0;
                while (iterator.hasNext()) {
                    this.globalContext.put(format("global[%d]", i), String.valueOf(iterator.next()));
                    i++;
                }
            } else if (parsed instanceof JSONObject) {
                JSONObject parsedObject = (JSONObject) parsed;
                for (Object key : parsedObject.keySet()) {
                    this.globalContext.put(String.valueOf(key), String.valueOf(parsedObject.get(key)));
                }
            } else {
                System.err.println("Unable to handle context type: " + parsed.getClass());
            }
        }
    }

    /**
     * Use this method to test the log appender. First, run the VerySimpleLogger.
     *
     * @param args Program arguments. None are needed.
     * @throws java.lang.Exception if things go wrong
     */
    public static void main(String[] args) throws Exception {
        Logger logger = Logger.getLogger(GlobalContextSocketAppender.class);
        logger.info("here you go");
        logger.debug("this is fun");

        System.out.println("Sleeping...");
        Thread.sleep(5000);
        System.out.println("Exiting...");
        System.exit(0);
    }
}