Apache Log4j Core Implementation provides the functional components of the logging system. Users are free to create their own plugins and include them in the logging configuration. Apache Log4j Core is a required module to use Apache Log4j.

Bytecode (Java 8) for Apache Log4j Core Implementation is provided in a separate JAR file like log4j-core-2.14.1.jar.

Source Code files for Apache Log4j API are provided in both binary packge like apache-log4j-2.14.1-bin.zip and source package like apache-log4j-2.14.1-src.zip. You can download them at Apache Log4j Website.

You can also browse Source Code files for Apache Log4j Core Implementation 2.14.1 below.

⏎ org/apache/logging/log4j/core/appender/db/AbstractDatabaseManager.java

/*
 * 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
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the license for the specific language governing permissions and
 * limitations under the license.
 */

package org.apache.logging.log4j.core.appender.db;

import java.io.Flushable;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.concurrent.TimeUnit;

import org.apache.logging.log4j.core.Layout;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.appender.AbstractManager;
import org.apache.logging.log4j.core.appender.ManagerFactory;

/**
 * Manager that allows database appenders to have their configuration reloaded without losing events.
 */
public abstract class AbstractDatabaseManager extends AbstractManager implements Flushable {
    
    /**
     * Implementations should extend this class for passing data between the getManager method and the manager factory
     * class.
     */
    protected abstract static class AbstractFactoryData {
        private final int bufferSize;
        private final Layout<? extends Serializable> layout;

        /**
         * Constructs the base factory data.
         *
         * @param bufferSize The size of the buffer.
         * @param layout The appender-level layout
         */
        protected AbstractFactoryData(final int bufferSize, final Layout<? extends Serializable> layout) {
            this.bufferSize = bufferSize;
            this.layout = layout;
        }

        /**
         * Gets the buffer size.
         *
         * @return the buffer size.
         */
        public int getBufferSize() {
            return bufferSize;
        }

        /**
         * Gets the layout.
         *
         * @return the layout.
         */
        public Layout<? extends Serializable> getLayout() {
            return layout;
        }
    }
    /**
     * Implementations should define their own getManager method and call this method from that to create or get
     * existing managers.
     *
     * @param name The manager name, which should include any configuration details that one might want to be able to
     *             reconfigure at runtime, such as database name, username, (hashed) password, etc.
     * @param data The concrete instance of {@link AbstractFactoryData} appropriate for the given manager.
     * @param factory A factory instance for creating the appropriate manager.
     * @param <M> The concrete manager type.
     * @param <T> The concrete {@link AbstractFactoryData} type.
     * @return a new or existing manager of the specified type and name.
     */
    protected static <M extends AbstractDatabaseManager, T extends AbstractFactoryData> M getManager(
            final String name, final T data, final ManagerFactory<M, T> factory
    ) {
        return AbstractManager.getManager(name, factory, data);
    }
    private final ArrayList<LogEvent> buffer;
    private final int bufferSize;

    private final Layout<? extends Serializable> layout;

    private boolean running;

    /**
     * Instantiates the base manager.
     *
     * @param name The manager name, which should include any configuration details that one might want to be able to
     *             reconfigure at runtime, such as database name, username, (hashed) password, etc.
     * @param bufferSize The size of the log event buffer.
     */
    protected AbstractDatabaseManager(final String name, final int bufferSize) {
        this(name, bufferSize, null);
    }

    /**
     * Instantiates the base manager.
     *
     * @param name The manager name, which should include any configuration details that one might want to be able to
     *             reconfigure at runtime, such as database name, username, (hashed) password, etc.
     * @param layout the Appender-level layout.
     * @param bufferSize The size of the log event buffer.
     */
    protected AbstractDatabaseManager(final String name, final int bufferSize, final Layout<? extends Serializable> layout) {
        super(null, name);
        this.bufferSize = bufferSize;
        this.buffer = new ArrayList<>(bufferSize + 1);
        this.layout = layout;
    }

    protected void buffer(final LogEvent event) {
        this.buffer.add(event.toImmutable());
        if (this.buffer.size() >= this.bufferSize || event.isEndOfBatch()) {
            this.flush();
        }
    }

    /**
     * Commits any active transaction (if applicable) and disconnects from the database (returns the connection to the
     * connection pool). With buffering enabled, this is called when flushing the buffer completes, after the last call
     * to {@link #writeInternal}. With buffering disabled, this is called immediately after every invocation of
     * {@link #writeInternal}.
     * @return true if all resources were closed normally, false otherwise.
     */
    protected abstract boolean commitAndClose();

    /**
     * Connects to the database and starts a transaction (if applicable). With buffering enabled, this is called when
     * flushing the buffer begins, before the first call to {@link #writeInternal}. With buffering disabled, this is
     * called immediately before every invocation of {@link #writeInternal}.
     */
    protected abstract void connectAndStart();

    /**
     * This method is called automatically when the buffer size reaches its maximum or at the beginning of a call to
     * {@link #shutdown()}. It can also be called manually to flush events to the database.
     */
    @Override
    public final synchronized void flush() {
        if (this.isRunning() && isBuffered()) {
            this.connectAndStart();
            try {
                for (final LogEvent event : this.buffer) {
                    this.writeInternal(event, layout != null ? layout.toSerializable(event) : null);
                }
            } finally {
                this.commitAndClose();
                // not sure if this should be done when writing the events failed
                this.buffer.clear();
            }
        }
    }

    protected boolean isBuffered() {
        return this.bufferSize > 0;
    }

    /**
     * Indicates whether the manager is currently connected {@link #startup()} has been called and {@link #shutdown()}
     * has not been called).
     *
     * @return {@code true} if the manager is connected.
     */
    public final boolean isRunning() {
        return this.running;
    }

    @Override
    public final boolean releaseSub(final long timeout, final TimeUnit timeUnit) {
        return this.shutdown();
    }

    /**
     * This method is called from the {@link #close()} method when the appender is stopped or the appender's manager
     * is replaced. If it has not already been called, it calls {@link #shutdownInternal()} and catches any exceptions
     * it might throw.
     * @return true if all resources were closed normally, false otherwise.
     */
    public final synchronized boolean shutdown() {
        boolean closed = true;
        this.flush();
        if (this.isRunning()) {
            try {
                closed &= this.shutdownInternal();
            } catch (final Exception e) {
                logWarn("Caught exception while performing database shutdown operations", e);
                closed = false;
            } finally {
                this.running = false;
            }
        }
        return closed;
    }

    /**
     * Implementations should implement this method to perform any proprietary disconnection / shutdown operations. This
     * method will never be called twice on the same instance, and it will only be called <em>after</em>
     * {@link #startupInternal()}. It is safe to throw any exceptions from this method. This method does not
     * necessarily disconnect from the database for the same reasons outlined in {@link #startupInternal()}.
     * @return true if all resources were closed normally, false otherwise.
     */
    protected abstract boolean shutdownInternal() throws Exception;

    /**
     * This method is called within the appender when the appender is started. If it has not already been called, it
     * calls {@link #startupInternal()} and catches any exceptions it might throw.
     */
    public final synchronized void startup() {
        if (!this.isRunning()) {
            try {
                this.startupInternal();
                this.running = true;
            } catch (final Exception e) {
                logError("Could not perform database startup operations", e);
            }
        }
    }

    /**
     * Implementations should implement this method to perform any proprietary startup operations. This method will
     * never be called twice on the same instance. It is safe to throw any exceptions from this method. This method
     * does not necessarily connect to the database, as it is generally unreliable to connect once and use the same
     * connection for hours.
     */
    protected abstract void startupInternal() throws Exception;

    @Override
    public final String toString() {
        return this.getName();
    }

    /**
     * This method manages buffering and writing of events.
     *
     * @param event The event to write to the database.
     * @deprecated since 2.11.0 Use {@link #write(LogEvent, Serializable)}.
     */
    @Deprecated
    public final synchronized void write(final LogEvent event) {
        write(event, null);
    }
    
    /**
     * This method manages buffering and writing of events.
     *
     * @param event The event to write to the database.
     * @param serializable Serializable event
     */
    public final synchronized void write(final LogEvent event, final Serializable serializable) {
        if (isBuffered()) {
            buffer(event);
        } else {
            writeThrough(event, serializable);
        }
    }

    /**
     * Performs the actual writing of the event in an implementation-specific way. This method is called immediately
     * from {@link #write(LogEvent, Serializable)} if buffering is off, or from {@link #flush()} if the buffer has reached its limit.
     *
     * @param event The event to write to the database.
     * @deprecated Use {@link #writeInternal(LogEvent, Serializable)}.
     */
    @Deprecated
    protected void writeInternal(final LogEvent event) {
        writeInternal(event, null);
    }

    /**
     * Performs the actual writing of the event in an implementation-specific way. This method is called immediately
     * from {@link #write(LogEvent, Serializable)} if buffering is off, or from {@link #flush()} if the buffer has reached its limit.
     *
     * @param event The event to write to the database.
     */
    protected abstract void writeInternal(LogEvent event, Serializable serializable);

    protected void writeThrough(final LogEvent event, final Serializable serializable) {
        this.connectAndStart();
        try {
            this.writeInternal(event, serializable);
        } finally {
            this.commitAndClose();
        }
    }
}

⏎ org/apache/logging/log4j/core/appender/db/AbstractDatabaseManager.java

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File name: log4j-core-2.14.1-sources.jar
File size: 1281358 bytes
Release date: 2021-03-06
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