[ 
https://issues.apache.org/jira/browse/LOG4J2-1217?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Thies Wellpott updated LOG4J2-1217:
-----------------------------------
    Description: 
PatternLayout does not provide the ability to limit the length of the text 
without space padding (with the numbers directly after the %).

The following Converter provides this possibility:
{{%maxLen\{pattern}\{max. length\}}}, e.g. {{%maxLen\{%m}\{90\}}}
use {{%maxLen}} or {{%maxLength}}

{code:title=MaxLengthConverter.java}
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);
    }

}
{code}

You may include this in log4j2

  was:
PatternLayout does not provide the ability to limit the length of the text 
without space padding (with the numbers directly after the %).

The following Converter provides this possibliity:
{{%maxLen\{pattern}\{max. length}}}, e.g. {{%maxLen\{%m}\{90}}}
use {{%maxLen}} or {{%maxLength}}

{code:title=MaxLengthConverter.java}
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);
    }

}
{code}

You may include this in log4j2


> Layout option to limit length of text
> -------------------------------------
>
>                 Key: LOG4J2-1217
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-1217
>             Project: Log4j 2
>          Issue Type: Improvement
>          Components: Pattern Converters
>    Affects Versions: 2.4.1
>            Reporter: Thies Wellpott
>
> PatternLayout does not provide the ability to limit the length of the text 
> without space padding (with the numbers directly after the %).
> The following Converter provides this possibility:
> {{%maxLen\{pattern}\{max. length\}}}, e.g. {{%maxLen\{%m}\{90\}}}
> use {{%maxLen}} or {{%maxLength}}
> {code:title=MaxLengthConverter.java}
> 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);
>     }
> }
> {code}
> You may include this in log4j2



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