Source Code for Apache Log4j Core Implementation

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.

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org/apache/logging/log4j/core/impl/Log4jContextFactory.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.impl;

import java.net.URI;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Objects;

import org.apache.logging.log4j.core.LifeCycle;
import org.apache.logging.log4j.core.LoggerContext;
import org.apache.logging.log4j.core.config.AbstractConfiguration;
import org.apache.logging.log4j.core.config.DefaultConfiguration;
import org.apache.logging.log4j.core.config.composite.CompositeConfiguration;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.ConfigurationFactory;
import org.apache.logging.log4j.core.config.ConfigurationSource;
import org.apache.logging.log4j.core.selector.ClassLoaderContextSelector;
import org.apache.logging.log4j.core.selector.ContextSelector;
import org.apache.logging.log4j.core.util.Cancellable;
import org.apache.logging.log4j.core.util.Constants;
import org.apache.logging.log4j.core.util.DefaultShutdownCallbackRegistry;
import org.apache.logging.log4j.core.util.Loader;
import org.apache.logging.log4j.core.util.ShutdownCallbackRegistry;
import org.apache.logging.log4j.spi.LoggerContextFactory;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.PropertiesUtil;

/**
 * Factory to locate a ContextSelector and then load a LoggerContext.
 */
public class Log4jContextFactory implements LoggerContextFactory, ShutdownCallbackRegistry {

    private static final StatusLogger LOGGER = StatusLogger.getLogger();
    private static final boolean SHUTDOWN_HOOK_ENABLED =
        PropertiesUtil.getProperties().getBooleanProperty(ShutdownCallbackRegistry.SHUTDOWN_HOOK_ENABLED, true) &&
                !Constants.IS_WEB_APP;

    private final ContextSelector selector;
    private final ShutdownCallbackRegistry shutdownCallbackRegistry;

    /**
     * Initializes the ContextSelector from system property {@link Constants#LOG4J_CONTEXT_SELECTOR}.
     */
    public Log4jContextFactory() {
        this(createContextSelector(), createShutdownCallbackRegistry());
    }

    /**
     * Initializes this factory's ContextSelector with the specified selector.
     * @param selector the selector to use
     */
    public Log4jContextFactory(final ContextSelector selector) {
        this(selector, createShutdownCallbackRegistry());
    }

    /**
     * Constructs a Log4jContextFactory using the ContextSelector from {@link Constants#LOG4J_CONTEXT_SELECTOR}
     * and the provided ShutdownRegistrationStrategy.
     *
     * @param shutdownCallbackRegistry the ShutdownRegistrationStrategy to use
     * @since 2.1
     */
    public Log4jContextFactory(final ShutdownCallbackRegistry shutdownCallbackRegistry) {
        this(createContextSelector(), shutdownCallbackRegistry);
    }

    /**
     * Constructs a Log4jContextFactory using the provided ContextSelector and ShutdownRegistrationStrategy.
     *
     * @param selector                     the selector to use
     * @param shutdownCallbackRegistry the ShutdownRegistrationStrategy to use
     * @since 2.1
     */
    public Log4jContextFactory(final ContextSelector selector,
                               final ShutdownCallbackRegistry shutdownCallbackRegistry) {
        this.selector = Objects.requireNonNull(selector, "No ContextSelector provided");
        this.shutdownCallbackRegistry = Objects.requireNonNull(shutdownCallbackRegistry, "No ShutdownCallbackRegistry provided");
        LOGGER.debug("Using ShutdownCallbackRegistry {}", shutdownCallbackRegistry.getClass());
        initializeShutdownCallbackRegistry();
    }

    private static ContextSelector createContextSelector() {
        try {
            final ContextSelector selector = Loader.newCheckedInstanceOfProperty(Constants.LOG4J_CONTEXT_SELECTOR,
                ContextSelector.class);
            if (selector != null) {
                return selector;
            }
        } catch (final Exception e) {
            LOGGER.error("Unable to create custom ContextSelector. Falling back to default.", e);
        }
        return new ClassLoaderContextSelector();
    }

    private static ShutdownCallbackRegistry createShutdownCallbackRegistry() {
        try {
            final ShutdownCallbackRegistry registry = Loader.newCheckedInstanceOfProperty(
                ShutdownCallbackRegistry.SHUTDOWN_CALLBACK_REGISTRY, ShutdownCallbackRegistry.class
            );
            if (registry != null) {
                return registry;
            }
        } catch (final Exception e) {
            LOGGER.error("Unable to create custom ShutdownCallbackRegistry. Falling back to default.", e);
        }
        return new DefaultShutdownCallbackRegistry();
    }

    private void initializeShutdownCallbackRegistry() {
        if (isShutdownHookEnabled() && this.shutdownCallbackRegistry instanceof LifeCycle) {
            try {
                ((LifeCycle) this.shutdownCallbackRegistry).start();
            } catch (final IllegalStateException e) {
                LOGGER.error("Cannot start ShutdownCallbackRegistry, already shutting down.");
                throw e;
            } catch (final RuntimeException e) {
                LOGGER.error("There was an error starting the ShutdownCallbackRegistry.", e);
            }
        }
    }

    /**
     * Loads the LoggerContext using the ContextSelector.
     * @param fqcn The fully qualified class name of the caller.
     * @param loader The ClassLoader to use or null.
     * @param currentContext If true returns the current Context, if false returns the Context appropriate
     * for the caller if a more appropriate Context can be determined.
     * @param externalContext An external context (such as a ServletContext) to be associated with the LoggerContext.
     * @return The LoggerContext.
     */
    @Override
    public LoggerContext getContext(final String fqcn, final ClassLoader loader, final Object externalContext,
                                    final boolean currentContext) {
        final LoggerContext ctx = selector.getContext(fqcn, loader, currentContext);
        if (externalContext != null && ctx.getExternalContext() == null) {
            ctx.setExternalContext(externalContext);
        }
        if (ctx.getState() == LifeCycle.State.INITIALIZED) {
            ctx.start();
        }
        return ctx;
    }

    /**
     * Loads the LoggerContext using the ContextSelector.
     * @param fqcn The fully qualified class name of the caller.
     * @param loader The ClassLoader to use or null.
     * @param externalContext An external context (such as a ServletContext) to be associated with the LoggerContext.
     * @param currentContext If true returns the current Context, if false returns the Context appropriate
     * for the caller if a more appropriate Context can be determined.
     * @param source The configuration source.
     * @return The LoggerContext.
     */
    public LoggerContext getContext(final String fqcn, final ClassLoader loader, final Object externalContext,
                                    final boolean currentContext, final ConfigurationSource source) {
        final LoggerContext ctx = selector.getContext(fqcn, loader, currentContext, null);
        if (externalContext != null && ctx.getExternalContext() == null) {
            ctx.setExternalContext(externalContext);
        }
        if (ctx.getState() == LifeCycle.State.INITIALIZED) {
            if (source != null) {
                ContextAnchor.THREAD_CONTEXT.set(ctx);
                final Configuration config = ConfigurationFactory.getInstance().getConfiguration(ctx, source);
                LOGGER.debug("Starting LoggerContext[name={}] from configuration {}", ctx.getName(), source);
                ctx.start(config);
                ContextAnchor.THREAD_CONTEXT.remove();
            } else {
                ctx.start();
            }
        }
        return ctx;
    }

    /**
     * Loads the LoggerContext using the ContextSelector using the provided Configuration
     * @param fqcn The fully qualified class name of the caller.
     * @param loader The ClassLoader to use or null.
     * @param externalContext An external context (such as a ServletContext) to be associated with the LoggerContext.
     * @param currentContext If true returns the current Context, if false returns the Context appropriate
     * for the caller if a more appropriate Context can be determined.
     * @param configuration The Configuration.
     * @return The LoggerContext.
     */
    public LoggerContext getContext(final String fqcn, final ClassLoader loader, final Object externalContext,
            final boolean currentContext, final Configuration configuration) {
        final LoggerContext ctx = selector.getContext(fqcn, loader, currentContext, null);
        if (externalContext != null && ctx.getExternalContext() == null) {
            ctx.setExternalContext(externalContext);
        }
        if (ctx.getState() == LifeCycle.State.INITIALIZED) {
            ContextAnchor.THREAD_CONTEXT.set(ctx);
            try {
                ctx.start(configuration);
            } finally {
                ContextAnchor.THREAD_CONTEXT.remove();
            }
        }
        return ctx;
    }

    /**
     * Loads the LoggerContext using the ContextSelector.
     * @param fqcn The fully qualified class name of the caller.
     * @param loader The ClassLoader to use or null.
     * @param externalContext An external context (such as a ServletContext) to be associated with the LoggerContext.
     * @param currentContext If true returns the current Context, if false returns the Context appropriate
     * for the caller if a more appropriate Context can be determined.
     * @param configLocation The location of the configuration for the LoggerContext (or null).
     * @return The LoggerContext.
     */
    @Override
    public LoggerContext getContext(final String fqcn, final ClassLoader loader, final Object externalContext,
                                    final boolean currentContext, final URI configLocation, final String name) {
        final LoggerContext ctx = selector.getContext(fqcn, loader, currentContext, configLocation);
        if (externalContext != null && ctx.getExternalContext() == null) {
            ctx.setExternalContext(externalContext);
        }
        if (name != null) {
        	ctx.setName(name);
        }
        if (ctx.getState() == LifeCycle.State.INITIALIZED) {
            if (configLocation != null || name != null) {
                ContextAnchor.THREAD_CONTEXT.set(ctx);
                final Configuration config = ConfigurationFactory.getInstance().getConfiguration(ctx, name, configLocation);
                LOGGER.debug("Starting LoggerContext[name={}] from configuration at {}", ctx.getName(), configLocation);
                ctx.start(config);
                ContextAnchor.THREAD_CONTEXT.remove();
            } else {
                ctx.start();
            }
        }
        return ctx;
    }

    public LoggerContext getContext(final String fqcn, final ClassLoader loader, final Map.Entry<String, Object> entry,
            final boolean currentContext, final URI configLocation, final String name) {
        final LoggerContext ctx = selector.getContext(fqcn, loader, entry, currentContext, configLocation);
        if (name != null) {
            ctx.setName(name);
        }
        if (ctx.getState() == LifeCycle.State.INITIALIZED) {
            if (configLocation != null || name != null) {
                ContextAnchor.THREAD_CONTEXT.set(ctx);
                final Configuration config = ConfigurationFactory.getInstance().getConfiguration(ctx, name, configLocation);
                LOGGER.debug("Starting LoggerContext[name={}] from configuration at {}", ctx.getName(), configLocation);
                ctx.start(config);
                ContextAnchor.THREAD_CONTEXT.remove();
            } else {
                ctx.start();
            }
        }
        return ctx;
    }

    public LoggerContext getContext(final String fqcn, final ClassLoader loader, final Object externalContext,
            final boolean currentContext, final List<URI> configLocations, final String name) {
        final LoggerContext ctx = selector
                .getContext(fqcn, loader, currentContext, null/*this probably needs to change*/);
        if (externalContext != null && ctx.getExternalContext() == null) {
            ctx.setExternalContext(externalContext);
        }
        if (name != null) {
            ctx.setName(name);
        }
        if (ctx.getState() == LifeCycle.State.INITIALIZED) {
            if ((configLocations != null && !configLocations.isEmpty())) {
                ContextAnchor.THREAD_CONTEXT.set(ctx);
                final List<AbstractConfiguration> configurations = new ArrayList<>(configLocations.size());
                for (final URI configLocation : configLocations) {
                    final Configuration currentReadConfiguration = ConfigurationFactory.getInstance()
                            .getConfiguration(ctx, name, configLocation);
                    if (currentReadConfiguration != null) {
                        if (currentReadConfiguration instanceof DefaultConfiguration) {
                            LOGGER.warn("Unable to locate configuration {}, ignoring", configLocation.toString());
                        }
                        else if (currentReadConfiguration instanceof AbstractConfiguration) {
                            configurations.add((AbstractConfiguration) currentReadConfiguration);
                        } else {
                            LOGGER.error(
                                    "Found configuration {}, which is not an AbstractConfiguration and can't be handled by CompositeConfiguration",
                                    configLocation);
                        }
                    } else {
                        LOGGER.info("Unable to access configuration {}, ignoring", configLocation.toString());
                    }
                }
                if (configurations.isEmpty()) {
                    LOGGER.error("No configurations could be created for {}", configLocations.toString());
                } else if (configurations.size() == 1) {
                    AbstractConfiguration config = configurations.get(0);
                    LOGGER.debug("Starting LoggerContext[name={}] from configuration at {}", ctx.getName(),
                            config.getConfigurationSource().getLocation());
                    ctx.start(config);
                } else {
                    final CompositeConfiguration compositeConfiguration = new CompositeConfiguration(configurations);
                    LOGGER.debug("Starting LoggerContext[name={}] from configurations at {}", ctx.getName(),
                            configLocations);
                    ctx.start(compositeConfiguration);
                }

                ContextAnchor.THREAD_CONTEXT.remove();
            } else {
                ctx.start();
            }
        }
        return ctx;
    }

    @Override
    public void shutdown(String fqcn, ClassLoader loader, boolean currentContext, boolean allContexts) {
        if (selector.hasContext(fqcn, loader, currentContext)) {
            selector.shutdown(fqcn, loader, currentContext, allContexts);
        }
    }

    /**
     * Checks to see if a LoggerContext is installed.
     * @param fqcn The fully qualified class name of the caller.
     * @param loader The ClassLoader to use or null.
     * @param currentContext If true returns the current Context, if false returns the Context appropriate
     * for the caller if a more appropriate Context can be determined.
     * @return true if a LoggerContext has been installed, false otherwise.
     * @since 3.0
     */
    @Override
    public boolean hasContext(String fqcn, ClassLoader loader, boolean currentContext) {
        return selector.hasContext(fqcn, loader, currentContext);
    }

    /**
     * Returns the ContextSelector.
     * @return The ContextSelector.
     */
    public ContextSelector getSelector() {
        return selector;
    }

	/**
	 * Returns the ShutdownCallbackRegistry
	 *
	 * @return the ShutdownCallbackRegistry
	 * @since 2.4
	 */
	public ShutdownCallbackRegistry getShutdownCallbackRegistry() {
		return shutdownCallbackRegistry;
	}

    /**
     * Removes knowledge of a LoggerContext.
     *
     * @param context The context to remove.
     */
    @Override
    public void removeContext(final org.apache.logging.log4j.spi.LoggerContext context) {
        if (context instanceof LoggerContext) {
            selector.removeContext((LoggerContext) context);
        }
    }

    @Override
    public Cancellable addShutdownCallback(final Runnable callback) {
        return isShutdownHookEnabled() ? shutdownCallbackRegistry.addShutdownCallback(callback) : null;
    }

    public boolean isShutdownHookEnabled() {
        return SHUTDOWN_HOOK_ENABLED;
    }
}

org/apache/logging/log4j/core/impl/Log4jContextFactory.java

 

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