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/util/OptionConverter.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.util;

import java.io.InterruptedIOException;
import java.util.Locale;
import java.util.Properties;

import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.PropertiesUtil;
import org.apache.logging.log4j.util.Strings;

/**
 * A convenience class to convert property values to specific types.
 */
public final class OptionConverter {

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

    private static final String DELIM_START = "${";
    private static final char DELIM_STOP = '}';
    private static final int DELIM_START_LEN = 2;
    private static final int DELIM_STOP_LEN = 1;
    private static final int ONE_K = 1024;

    /**
     * OptionConverter is a static class.
     */
    private OptionConverter() {
    }

    public static String[] concatenateArrays(final String[] l, final String[] r) {
        final int len = l.length + r.length;
        final String[] a = new String[len];

        System.arraycopy(l, 0, a, 0, l.length);
        System.arraycopy(r, 0, a, l.length, r.length);

        return a;
    }

    public static String convertSpecialChars(final String s) {
        char c;
        final int len = s.length();
        final StringBuilder sbuf = new StringBuilder(len);

        int i = 0;
        while (i < len) {
            c = s.charAt(i++);
            if (c == '\\') {
                c = s.charAt(i++);
                switch (c) {
                case 'n':
                    c = '\n';
                    break;
                case 'r':
                    c = '\r';
                    break;
                case 't':
                    c = '\t';
                    break;
                case 'f':
                    c = '\f';
                    break;
                case 'b':
                    c = '\b';
                    break;
                case '"':
                    c = '\"';
                    break;
                case '\'':
                    c = '\'';
                    break;
                case '\\':
                    c = '\\';
                    break;
                default:
                    // there is no default case.
                }
            }
            sbuf.append(c);
        }
        return sbuf.toString();
    }

    public static Object instantiateByKey(final Properties props, final String key, final Class<?> superClass,
                                   final Object defaultValue) {

        // Get the value of the property in string form
        final String className = findAndSubst(key, props);
        if (className == null) {
            LOGGER.error("Could not find value for key {}", key);
            return defaultValue;
        }
        // Trim className to avoid trailing spaces that cause problems.
        return OptionConverter.instantiateByClassName(className.trim(), superClass,
            defaultValue);
    }

    /**
     * If <code>value</code> is "true", then {@code true} is
     * returned. If <code>value</code> is "false", then
     * {@code false} is returned. Otherwise, <code>default</code> is
     * returned.
     *
     * <p>Case of value is unimportant.</p>
     * @param value The value to convert.
     * @param defaultValue The default value.
     * @return true or false, depending on the value and/or default.
     */
    public static boolean toBoolean(final String value, final boolean defaultValue) {
        if (value == null) {
            return defaultValue;
        }
        final String trimmedVal = value.trim();
        if ("true".equalsIgnoreCase(trimmedVal)) {
            return true;
        }
        if ("false".equalsIgnoreCase(trimmedVal)) {
            return false;
        }
        return defaultValue;
    }

    /**
     * Convert the String value to an int.
     * @param value The value as a String.
     * @param defaultValue The default value.
     * @return The value as an int.
     */
    public static int toInt(final String value, final int defaultValue) {
        if (value != null) {
            final String s = value.trim();
            try {
                return Integer.parseInt(s);
            } catch (final NumberFormatException e) {
                LOGGER.error("[{}] is not in proper int form.", s, e);
            }
        }
        return defaultValue;
    }

    public static Level toLevel(String value, Level defaultValue) {
        if(value == null) {
            return defaultValue;
        }

        value = value.trim();

        int hashIndex = value.indexOf('#');
        if (hashIndex == -1) {
            if("NULL".equalsIgnoreCase(value)) {
                return null;
            } else {
                // no class name specified : use standard Level class
                return Level.toLevel(value, defaultValue);
            }
        }

        Level result = defaultValue;

        String clazz = value.substring(hashIndex+1);
        String levelName = value.substring(0, hashIndex);

        // This is degenerate case but you never know.
        if("NULL".equalsIgnoreCase(levelName)) {
            return null;
        }

        LOGGER.debug("toLevel" + ":class=[" + clazz + "]"
            + ":pri=[" + levelName + "]");

        try {
            Class<?> customLevel = Loader.loadClass(clazz);

            // get a ref to the specified class' static method
            // toLevel(String, org.apache.log4j.Level)
            Class<?>[] paramTypes = new Class[] { String.class, Level.class };
            java.lang.reflect.Method toLevelMethod =
                customLevel.getMethod("toLevel", paramTypes);

            // now call the toLevel method, passing level string + default
            Object[] params = new Object[] {levelName, defaultValue};
            Object o = toLevelMethod.invoke(null, params);

            result = (Level) o;
        } catch(ClassNotFoundException e) {
            LOGGER.warn("custom level class [" + clazz + "] not found.");
        } catch(NoSuchMethodException e) {
            LOGGER.warn("custom level class [" + clazz + "]"
                + " does not have a class function toLevel(String, Level)", e);
        } catch(java.lang.reflect.InvocationTargetException e) {
            if (e.getTargetException() instanceof InterruptedException
                || e.getTargetException() instanceof InterruptedIOException) {
                Thread.currentThread().interrupt();
            }
            LOGGER.warn("custom level class [" + clazz + "]" + " could not be instantiated", e);
        } catch(ClassCastException e) {
            LOGGER.warn("class [" + clazz + "] is not a subclass of org.apache.log4j.Level", e);
        } catch(IllegalAccessException e) {
            LOGGER.warn("class ["+clazz+ "] cannot be instantiated due to access restrictions", e);
        } catch(RuntimeException e) {
            LOGGER.warn("class ["+clazz+"], level [" + levelName + "] conversion failed.", e);
        }
        return result;
    }

    /**
     *
     * @param value The size of the file as a String.
     * @param defaultValue The default value.
     * @return The size of the file as a long.
     */
    public static long toFileSize(final String value, final long defaultValue) {
        if (value == null) {
            return defaultValue;
        }

        String str = value.trim().toUpperCase(Locale.ENGLISH);
        long multiplier = 1;
        int index;

        if ((index = str.indexOf("KB")) != -1) {
            multiplier = ONE_K;
            str = str.substring(0, index);
        } else if ((index = str.indexOf("MB")) != -1) {
            multiplier = ONE_K * ONE_K;
            str = str.substring(0, index);
        } else if ((index = str.indexOf("GB")) != -1) {
            multiplier = ONE_K * ONE_K * ONE_K;
            str = str.substring(0, index);
        }
        try {
            return Long.parseLong(str) * multiplier;
        } catch (final NumberFormatException e) {
            LOGGER.error("[{}] is not in proper int form.", str);
            LOGGER.error("[{}] not in expected format.", value, e);
        }
        return defaultValue;
    }

    /**
     * Find the value corresponding to <code>key</code> in
     * <code>props</code>. Then perform variable substitution on the
     * found value.
     * @param key The key to locate.
     * @param props The properties.
     * @return The String after substitution.
     */
    public static String findAndSubst(final String key, final Properties props) {
        final String value = props.getProperty(key);
        if (value == null) {
            return null;
        }

        try {
            return substVars(value, props);
        } catch (final IllegalArgumentException e) {
            LOGGER.error("Bad option value [{}].", value, e);
            return value;
        }
    }

    /**
     * Instantiate an object given a class name. Check that the
     * <code>className</code> is a subclass of
     * <code>superClass</code>. If that test fails or the object could
     * not be instantiated, then <code>defaultValue</code> is returned.
     *
     * @param className    The fully qualified class name of the object to instantiate.
     * @param superClass   The class to which the new object should belong.
     * @param defaultValue The object to return in case of non-fulfillment
     * @return The created object.
     */
    public static Object instantiateByClassName(final String className, final Class<?> superClass,
                                         final Object defaultValue) {
        if (className != null) {
            try {
                final Class<?> classObj = Loader.loadClass(className);
                if (!superClass.isAssignableFrom(classObj)) {
                    LOGGER.error("A \"{}\" object is not assignable to a \"{}\" variable.", className,
                        superClass.getName());
                    LOGGER.error("The class \"{}\" was loaded by [{}] whereas object of type [{}] was loaded by [{}].",
                        superClass.getName(), superClass.getClassLoader(), classObj.getName());
                    return defaultValue;
                }
                return classObj.newInstance();
            } catch (final Exception e) {
                LOGGER.error("Could not instantiate class [{}].", className, e);
            }
        }
        return defaultValue;
    }


    /**
     * Perform variable substitution in string <code>val</code> from the
     * values of keys found in the system propeties.
     *
     * <p>The variable substitution delimiters are <b>${</b> and <b>}</b>.</p>
     *
     * <p>For example, if the System properties contains "key=value", then
     * the call</p>
     * <pre>
     * String s = OptionConverter.substituteVars("Value of key is ${key}.");
     * </pre>
     * <p>
     * will set the variable <code>s</code> to "Value of key is value.".
     * </p>
     * <p>If no value could be found for the specified key, then the
     * <code>props</code> parameter is searched, if the value could not
     * be found there, then substitution defaults to the empty string.</p>
     *
     * <p>For example, if system properties contains no value for the key
     * "inexistentKey", then the call
     * </p>
     * <pre>
     * String s = OptionConverter.subsVars("Value of inexistentKey is [${inexistentKey}]");
     * </pre>
     * <p>
     * will set <code>s</code> to "Value of inexistentKey is []"
     * </p>
     * <p>An {@link java.lang.IllegalArgumentException} is thrown if
     * <code>val</code> contains a start delimeter "${" which is not
     * balanced by a stop delimeter "}". </p>
     *
     * @param val The string on which variable substitution is performed.
     * @param props The properties to use for substitution.
     * @return The String after substitution.
     * @throws IllegalArgumentException if <code>val</code> is malformed.
     */
    public static String substVars(final String val, final Properties props) throws
        IllegalArgumentException {

        final StringBuilder sbuf = new StringBuilder();

        int i = 0;
        int j;
        int k;

        while (true) {
            j = val.indexOf(DELIM_START, i);
            if (j == -1) {
                // no more variables
                if (i == 0) { // this is a simple string
                    return val;
                }
                // add the tail string which contails no variables and return the result.
                sbuf.append(val.substring(i, val.length()));
                return sbuf.toString();
            }
            sbuf.append(val.substring(i, j));
            k = val.indexOf(DELIM_STOP, j);
            if (k == -1) {
                throw new IllegalArgumentException(Strings.dquote(val)
                    + " has no closing brace. Opening brace at position " + j
                    + '.');
            }
            j += DELIM_START_LEN;
            final String key = val.substring(j, k);
            // first try in System properties
            String replacement = PropertiesUtil.getProperties().getStringProperty(key, null);
            // then try props parameter
            if (replacement == null && props != null) {
                replacement = props.getProperty(key);
            }

            if (replacement != null) {
                // Do variable substitution on the replacement string
                // such that we can solve "Hello ${x2}" as "Hello p1"
                // the where the properties are
                // x1=p1
                // x2=${x1}
                final String recursiveReplacement = substVars(replacement, props);
                sbuf.append(recursiveReplacement);
            }
            i = k + DELIM_STOP_LEN;
        }
    }
}

⏎ org/apache/logging/log4j/core/util/OptionConverter.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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