001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache license, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the license for the specific language governing permissions and
015 * limitations under the license.
016 */
017
018package org.apache.logging.log4j.core.pattern;
019
020import java.util.List;
021
022import org.apache.logging.log4j.core.LogEvent;
023import org.apache.logging.log4j.core.appender.AbstractAppender;
024import org.apache.logging.log4j.core.config.Configuration;
025import org.apache.logging.log4j.core.config.plugins.Plugin;
026import org.apache.logging.log4j.core.layout.PatternLayout;
027
028/**
029 * Max length pattern converter. Limit contained text to a maximum length.
030 * On invalid length the default value 100 is used (and an error message is logged).
031 * If max length is greater than 20, an abbreviated text will get ellipsis ("...") appended.
032 * Example usage (for email subject):
033 * {@code "%maxLen{[AppName, ${hostName}, ${web:contextPath}] %p: %c{1} - %m%notEmpty{ =>%ex{short}}}{160}"}
034 *
035 * @author Thies Wellpott
036 */
037@Plugin(name = "maxLength", category = PatternConverter.CATEGORY)
038@ConverterKeys({"maxLength", "maxLen"})
039public final class MaxLengthConverter extends LogEventPatternConverter {
040
041    /**
042     * Gets an instance of the class.
043     *
044     * @param config  The current Configuration.
045     * @param options pattern options, an array of two elements: pattern, max length (defaults to 100 on invalid value).
046     * @return instance of class.
047     */
048    public static MaxLengthConverter newInstance(final Configuration config, final String[] options) {
049        if (options.length != 2) {
050            LOGGER.error("Incorrect number of options on maxLength: expected 2 received {}: {}", options.length,
051                options);
052            return null;
053        }
054        if (options[0] == null) {
055            LOGGER.error("No pattern supplied on maxLength");
056            return null;
057        }
058        if (options[1] == null) {
059            LOGGER.error("No length supplied on maxLength");
060            return null;
061        }
062        final PatternParser parser = PatternLayout.createPatternParser(config);
063        final List<PatternFormatter> formatters = parser.parse(options[0]);
064        return new MaxLengthConverter(formatters, AbstractAppender.parseInt(options[1], 100));
065    }
066
067
068    private final List<PatternFormatter> formatters;
069    private final int maxLength;
070
071    /**
072     * Construct the converter.
073     *
074     * @param formatters The PatternFormatters to generate the text to manipulate.
075     * @param maxLength  The max. length of the resulting string. Ellipsis ("...") is appended on shorted string, if greater than 20.
076     */
077    private MaxLengthConverter(final List<PatternFormatter> formatters, final int maxLength) {
078        super("MaxLength", "maxLength");
079        this.maxLength = maxLength;
080        this.formatters = formatters;
081        LOGGER.trace("new MaxLengthConverter with {}", maxLength);
082    }
083
084
085    @Override
086    public void format(final LogEvent event, final StringBuilder toAppendTo) {
087        final StringBuilder buf = new StringBuilder();
088        for (final PatternFormatter formatter : formatters) {
089            formatter.format(event, buf);
090            if (buf.length() > maxLength) {        // stop early
091                break;
092            }
093        }
094        if (buf.length() > maxLength) {
095            buf.setLength(maxLength);
096            if (maxLength > 20) {        // only append ellipses if length is not very short
097                buf.append("...");
098            }
099        }
100        toAppendTo.append(buf);
101    }
102
103}