Source Code for Apache Log4j NoSQL Appenders

Apache Log4j NoSQL Appenders allows applications to send events to NoSQL repositories. To use it, you need both the log4j-nosql as well as the appropriate driver for your NoSQL database type.

Bytecode (Java 8) for Apache Log4j NoSQL Appenders is provided in a separate JAR file like log4j-nosql-2.3.jar.

Source Code files for Apache Log4j NoSQL Appenders are provided in both binary packge like and source package like You can download them at Apache Log4j Website.

You can also browse Source Code files for Apache Log4j NoSQL Appenders 2.3 below.



 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache license, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the license for the specific language governing permissions and
 * limitations under the license.
package org.apache.logging.log4j.nosql.appender.mongodb;

import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.appender.AppenderLoggingException;
import org.apache.logging.log4j.nosql.appender.NoSqlConnection;
import org.apache.logging.log4j.nosql.appender.NoSqlObject;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.Strings;
import org.bson.BSON;
import org.bson.Transformer;

import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.Mongo;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.WriteResult;

 * The MongoDB implementation of {@link NoSqlConnection}.
public final class MongoDbConnection implements NoSqlConnection<BasicDBObject, MongoDbObject> {

    private static final Logger LOGGER = StatusLogger.getLogger();

    static {
        BSON.addEncodingHook(Level.class, new Transformer() {
            public Object transform(final Object o) {
                if (o instanceof Level) {
                    return ((Level) o).name();
                return o;

    private final DBCollection collection;
    private final Mongo mongo;
    private final WriteConcern writeConcern;

    public MongoDbConnection(final DB database, final WriteConcern writeConcern, final String collectionName) {
        this.mongo = database.getMongo();
        this.collection = database.getCollection(collectionName);
        this.writeConcern = writeConcern;

    public MongoDbObject createObject() {
        return new MongoDbObject();

    public MongoDbObject[] createList(final int length) {
        return new MongoDbObject[length];

    public void insertObject(final NoSqlObject<BasicDBObject> object) {
        try {
            final WriteResult result = this.collection.insert(object.unwrap(), this.writeConcern);
            if (Strings.isNotEmpty(result.getError())) {
                throw new AppenderLoggingException("Failed to write log event to MongoDB due to error: " +
                        result.getError() + '.');
        } catch (final MongoException e) {
            throw new AppenderLoggingException("Failed to write log event to MongoDB due to error: " + e.getMessage(),

    public void close() {
        // there's no need to call this.mongo.close() since that literally closes the connection
        // MongoDBClient uses internal connection pooling
        // for more details, see LOG4J2-591

    public boolean isClosed() {
        return !this.mongo.getConnector().isOpen();

     * To prevent class loading issues during plugin discovery, this code cannot live within MongoDbProvider. This
     * is because of how Java treats references to Exception classes different from references to other classes. When
     * Java loads a class, it normally won't load that class's dependent classes until and unless A) they are used, B)
     * the class being loaded extends or implements those classes, or C) those classes are the types of static members
     * in the class. However, exceptions that a class uses are always loaded when the class is loaded, even before
     * they are actually used.
     * @param database The database to authenticate
     * @param username The username to authenticate with
     * @param password The password to authenticate with
    static void authenticate(final DB database, final String username, final String password) {
        try {
            if (!database.authenticate(username, password.toCharArray())) {
                LOGGER.error("Failed to authenticate against MongoDB server. Unknown error.");
        } catch (final MongoException e) {
            LOGGER.error("Failed to authenticate against MongoDB: " + e.getMessage(), e);
        } catch (final IllegalStateException e) {
            LOGGER.error("Factory-supplied MongoDB database connection already authenticated with different" +
                    "credentials but lost connection.", e);



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2015-11-04, 7937👍, 0💬