package de.ittw.log4j;
import java.util.List;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.appender.AbstractAppender;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.layout.PatternLayout;
import org.apache.logging.log4j.core.pattern.ConverterKeys;
import org.apache.logging.log4j.core.pattern.LogEventPatternConverter;
import org.apache.logging.log4j.core.pattern.PatternConverter;
import org.apache.logging.log4j.core.pattern.PatternFormatter;
import org.apache.logging.log4j.core.pattern.PatternParser;
 * Max length pattern converter. Limit contained text to a maximum length.
 * On invalid length the default value 100 is used (and an error message is logged).
 * If max length is greater than 20, an abbreviated text will get ellipsis ("...") appended.
 * Example usage (for email subject):
 *    "%maxLen{[AppName, ${hostName}, ${web:contextPath}] %p: %c{1} - %m%notEmpty{ =>%ex{short}}}{160}"
 * @author Thies Wellpott
@Plugin(name = "maxLength", category = PatternConverter.CATEGORY)
@ConverterKeys({ "maxLength", "maxLen" })
public final class MaxLengthConverter extends LogEventPatternConverter
     * Gets an instance of the class.
     * @param config
     *            The current Configuration.
     * @param options
     *            pattern options, an array of two elements: pattern, max length (defaults to 100 on invalid value).
     * @return instance of class.
    public static MaxLengthConverter newInstance(final Configuration config, final String[] options) {
        if (options.length != 2) {
            LOGGER.error("Incorrect number of options on maxLength: expected 2 received {}: {}", options.length, options);
            return null;
        if (options[0] == null) {
            LOGGER.error("No pattern supplied on maxLength");
            return null;
        if (options[1] == null) {
            LOGGER.error("No length supplied on maxLength");
            return null;
        final PatternParser parser = PatternLayout.createPatternParser(config);
        final List<PatternFormatter> formatters = parser.parse(options[0]);
        return new MaxLengthConverter(formatters, AbstractAppender.parseInt(options[1], 100));
    private final List<PatternFormatter> formatters;
    private final int maxLength;
     * Construct the converter.
     * @param formatters
     *            The PatternFormatters to generate the text to manipulate.
     * @param maxLength
     *            The max. length of the resultung string. Ellipses ("...") is appended on shorted string, if greater than 20.
    private MaxLengthConverter(final List<PatternFormatter> formatters, final int maxLength) {
        super("MaxLength", "maxLength");
        this.maxLength = maxLength;
        this.formatters = formatters;
        LOGGER.trace("new MaxLengthConverter with {}", maxLength);
    @Override
    public void format(final LogEvent event, final StringBuilder toAppendTo) {
        final StringBuilder buf = new StringBuilder();
        for (final PatternFormatter formatter : formatters) {
            formatter.format(event, buf);
            if (buf.length() > maxLength) {        // stop early
                break;
        if (buf.length() > maxLength) {
            buf.setLength(maxLength);
            if (maxLength > 20) {        // only append ellipses if length is not very short
                buf.append("...");
        toAppendTo.append(buf);
You may include this in log4j2