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;
027import org.apache.logging.log4j.util.PerformanceSensitive;
028
029/**
030 * Max length pattern converter. Limit contained text to a maximum length.
031 * On invalid length the default value 100 is used (and an error message is logged).
032 * If max length is greater than 20, an abbreviated text will get ellipsis ("...") appended.
033 * Example usage (for email subject):
034 * {@code "%maxLen{[AppName, ${hostName}, ${web:contextPath}] %p: %c{1} - %m%notEmpty{ =>%ex{short}}}{160}"}
035 *
036 * @author Thies Wellpott
037 */
038@Plugin(name = "maxLength", category = PatternConverter.CATEGORY)
039@ConverterKeys({"maxLength", "maxLen"})
040@PerformanceSensitive("allocation")
041public final class MaxLengthConverter extends LogEventPatternConverter {
042
043    /**
044     * Gets an instance of the class.
045     *
046     * @param config  The current Configuration.
047     * @param options pattern options, an array of two elements: pattern, max length (defaults to 100 on invalid value).
048     * @return instance of class.
049     */
050    public static MaxLengthConverter newInstance(final Configuration config, final String[] options) {
051        if (options.length != 2) {
052            LOGGER.error("Incorrect number of options on maxLength: expected 2 received {}: {}", options.length,
053                options);
054            return null;
055        }
056        if (options[0] == null) {
057            LOGGER.error("No pattern supplied on maxLength");
058            return null;
059        }
060        if (options[1] == null) {
061            LOGGER.error("No length supplied on maxLength");
062            return null;
063        }
064        final PatternParser parser = PatternLayout.createPatternParser(config);
065        final List<PatternFormatter> formatters = parser.parse(options[0]);
066        return new MaxLengthConverter(formatters, AbstractAppender.parseInt(options[1], 100));
067    }
068
069
070    private final List<PatternFormatter> formatters;
071    private final int maxLength;
072
073    /**
074     * Construct the converter.
075     *
076     * @param formatters The PatternFormatters to generate the text to manipulate.
077     * @param maxLength  The max. length of the resulting string. Ellipsis ("...") is appended on shorted string, if greater than 20.
078     */
079    private MaxLengthConverter(final List<PatternFormatter> formatters, final int maxLength) {
080        super("MaxLength", "maxLength");
081        this.maxLength = maxLength;
082        this.formatters = formatters;
083        LOGGER.trace("new MaxLengthConverter with {}", maxLength);
084    }
085
086
087    @Override
088    public void format(final LogEvent event, final StringBuilder toAppendTo) {
089        final int initialLength = toAppendTo.length();
090        for (int i = 0; i < formatters.size(); i++) {
091            final PatternFormatter formatter = formatters.get(i);
092            formatter.format(event, toAppendTo);
093            if (toAppendTo.length() > initialLength + maxLength) {        // stop early
094                break;
095            }
096        }
097        if (toAppendTo.length() > initialLength + maxLength) {
098            toAppendTo.setLength(initialLength + maxLength);
099            if (maxLength > 20) {        // only append ellipses if length is not very short
100                toAppendTo.append("...");
101            }
102        }
103    }
104}