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/pattern/ThrowablePatternConverter.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.pattern;

import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.impl.ThrowableFormatOptions;
import org.apache.logging.log4j.core.layout.PatternLayout;
import org.apache.logging.log4j.core.util.StringBuilderWriter;
import org.apache.logging.log4j.util.Strings;


/**
 * Outputs the Throwable portion of the LoggingEvent as a full stack trace
 * unless this converter's option is 'short', where it just outputs the first line of the trace, or if
 * the number of lines to print is explicitly specified.
 */
@Plugin(name = "ThrowablePatternConverter", category = PatternConverter.CATEGORY)
@ConverterKeys({ "ex", "throwable", "exception" })
public class ThrowablePatternConverter extends LogEventPatternConverter {

    /**
     * Lists {@link PatternFormatter}s for the suffix attribute.
     */
    protected final List<PatternFormatter> formatters;
    private String rawOption;
    private final boolean subShortOption;
    private final boolean nonStandardLineSeparator;

    /**
     * Options.
     */
    protected final ThrowableFormatOptions options;

    /**
     * Constructor.
     * @param name Name of converter.
     * @param style CSS style for output.
     * @param options options, may be null.
     * @deprecated Use ThrowablePatternConverter(String name, String stule, String[] options, Configuration config)
     */
    @Deprecated
    protected ThrowablePatternConverter(final String name, final String style, final String[] options) {
        this(name, style, options, null);
    }

    /**
     * Constructor.
     * @param name Name of converter.
     * @param style CSS style for output.
     * @param options options, may be null.
     * @param config
     */
    protected ThrowablePatternConverter(final String name, final String style, final String[] options, final Configuration config) {
        super(name, style);
        this.options = ThrowableFormatOptions.newInstance(options);
        if (options != null && options.length > 0) {
            rawOption = options[0];
        }
        if (this.options.getSuffix() != null) {
            final PatternParser parser = PatternLayout.createPatternParser(config);
            final List<PatternFormatter> parsedSuffixFormatters = parser.parse(this.options.getSuffix());
            // filter out nested formatters that will handle throwable
            boolean hasThrowableSuffixFormatter = false;
            for (final PatternFormatter suffixFormatter : parsedSuffixFormatters) {
                if (suffixFormatter.handlesThrowable()) {
                    hasThrowableSuffixFormatter = true;
                }
            }
            if (!hasThrowableSuffixFormatter) {
                this.formatters = parsedSuffixFormatters;
            } else {
                final List<PatternFormatter> suffixFormatters = new ArrayList<>();
                for (final PatternFormatter suffixFormatter : parsedSuffixFormatters) {
                    if (!suffixFormatter.handlesThrowable()) {
                        suffixFormatters.add(suffixFormatter);
                    }
                }
                this.formatters = suffixFormatters;
            }
        } else {
            this.formatters = Collections.emptyList();
        }
        subShortOption = ThrowableFormatOptions.MESSAGE.equalsIgnoreCase(rawOption) ||
                ThrowableFormatOptions.LOCALIZED_MESSAGE.equalsIgnoreCase(rawOption) ||
                ThrowableFormatOptions.FILE_NAME.equalsIgnoreCase(rawOption) ||
                ThrowableFormatOptions.LINE_NUMBER.equalsIgnoreCase(rawOption) ||
                ThrowableFormatOptions.METHOD_NAME.equalsIgnoreCase(rawOption) ||
                ThrowableFormatOptions.CLASS_NAME.equalsIgnoreCase(rawOption);
        nonStandardLineSeparator = !Strings.LINE_SEPARATOR.equals(this.options.getSeparator());
    }

    /**
     * Gets an instance of the class.
     *
     * @param config
     * @param options pattern options, may be null.  If first element is "short",
     *                only the first line of the throwable will be formatted.
     * @return instance of class.
     */
    public static ThrowablePatternConverter newInstance(final Configuration config, final String[] options) {
        return new ThrowablePatternConverter("Throwable", "throwable", options, config);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void format(final LogEvent event, final StringBuilder buffer) {
        final Throwable t = event.getThrown();

        if (subShortOption) {
            formatSubShortOption(t, getSuffix(event), buffer);
        }
        else if (t != null && options.anyLines()) {
            formatOption(t, getSuffix(event), buffer);
        }
    }

    private void formatSubShortOption(final Throwable t, final String suffix, final StringBuilder buffer) {
        StackTraceElement[] trace;
        StackTraceElement throwingMethod = null;
        int len;

        if (t != null) {
            trace = t.getStackTrace();
            if (trace !=null && trace.length > 0) {
                throwingMethod = trace[0];
            }
        }

        if (t != null && throwingMethod != null) {
            String toAppend = Strings.EMPTY;

            if (ThrowableFormatOptions.CLASS_NAME.equalsIgnoreCase(rawOption)) {
                toAppend = throwingMethod.getClassName();
            }
            else if (ThrowableFormatOptions.METHOD_NAME.equalsIgnoreCase(rawOption)) {
                toAppend = throwingMethod.getMethodName();
            }
            else if (ThrowableFormatOptions.LINE_NUMBER.equalsIgnoreCase(rawOption)) {
                toAppend = String.valueOf(throwingMethod.getLineNumber());
            }
            else if (ThrowableFormatOptions.MESSAGE.equalsIgnoreCase(rawOption)) {
                toAppend = t.getMessage();
            }
            else if (ThrowableFormatOptions.LOCALIZED_MESSAGE.equalsIgnoreCase(rawOption)) {
                toAppend = t.getLocalizedMessage();
            }
            else if (ThrowableFormatOptions.FILE_NAME.equalsIgnoreCase(rawOption)) {
                toAppend = throwingMethod.getFileName();
            }

            len = buffer.length();
            if (len > 0 && !Character.isWhitespace(buffer.charAt(len - 1))) {
                buffer.append(' ');
            }
            buffer.append(toAppend);

            if (Strings.isNotBlank(suffix)) {
                buffer.append(' ');
                buffer.append(suffix);
            }
        }
    }

    private void formatOption(final Throwable throwable, final String suffix, final StringBuilder buffer) {
        final int len = buffer.length();
        if (len > 0 && !Character.isWhitespace(buffer.charAt(len - 1))) {
            buffer.append(' ');
        }
        if (!options.allLines() || nonStandardLineSeparator || Strings.isNotBlank(suffix)) {
            final StringWriter w = new StringWriter();
            throwable.printStackTrace(new PrintWriter(w));

            final String[] array = w.toString().split(Strings.LINE_SEPARATOR);
            final int limit = options.minLines(array.length) - 1;
            final boolean suffixNotBlank = Strings.isNotBlank(suffix);
            for (int i = 0; i <= limit; ++i) {
                buffer.append(array[i]);
                if (suffixNotBlank) {
                    buffer.append(' ');
                    buffer.append(suffix);
                }
                if (i < limit) {
                    buffer.append(options.getSeparator());
                }
            }
        } else {
            throwable.printStackTrace(new PrintWriter(new StringBuilderWriter(buffer)));
        }
    }

    /**
     * This converter obviously handles throwables.
     *
     * @return true.
     */
    @Override
    public boolean handlesThrowable() {
        return true;
    }

    protected String getSuffix(final LogEvent event) {
        if (formatters.isEmpty()) {
            return Strings.EMPTY;
        }
        //noinspection ForLoopReplaceableByForEach
        final StringBuilder toAppendTo = new StringBuilder();
        for (int i = 0, size = formatters.size(); i <  size; i++) {
            formatters.get(i).format(event, toAppendTo);
        }
        return toAppendTo.toString();
    }

    public ThrowableFormatOptions getOptions() {
        return options;
    }
}

⏎ org/apache/logging/log4j/core/pattern/ThrowablePatternConverter.java

Or download all of them as a single archive file:

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