https://tomcat.apache.org/: Tomcat Servlet Engine Core Classes and Standard implementations 
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 * 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
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package org.apache.catalina.util;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.Properties;
import java.util.TimeZone;


Converts dates to strings using the same format specifiers as strftime
Note: This does not mimic strftime perfectly.  Certain strftime commands,
      are not supported, and will convert as if they were literals.
      Certain complicated commands, like those dealing with the week of the year
      probably don't have exactly the same behavior as strftime.
      These limitations are due to use SimpleDateTime.  If the conversion was done
      manually, all these limitations could be eliminated.
      The interface looks like a subset of DateFormat.  Maybe someday someone will make this class
      extend DateFormat.

Author:Bip Thelin, Dan Sandberg
/**
 * Converts dates to strings using the same format specifiers as strftime
 *
 * Note: This does not mimic strftime perfectly.  Certain strftime commands,
 *       are not supported, and will convert as if they were literals.
 *
 *       Certain complicated commands, like those dealing with the week of the year
 *       probably don't have exactly the same behavior as strftime.
 *
 *       These limitations are due to use SimpleDateTime.  If the conversion was done
 *       manually, all these limitations could be eliminated.
 *
 *       The interface looks like a subset of DateFormat.  Maybe someday someone will make this class
 *       extend DateFormat.
 *
 * @author Bip Thelin
 * @author Dan Sandberg
 */
public class Strftime {
    protected static final Properties translate;
    protected final SimpleDateFormat simpleDateFormat;

    
Initialize our pattern translation

/**
     * Initialize our pattern translation
     */
    static {
        translate = new Properties();
        translate.put("a","EEE");
        translate.put("A","EEEE");
        translate.put("b","MMM");
        translate.put("B","MMMM");
        translate.put("c","EEE MMM d HH:mm:ss yyyy");

        //There's no way to specify the century in SimpleDateFormat.  We don't want to hard-code
        //20 since this could be wrong for the pre-2000 files.
        //translate.put("C", "20");
        translate.put("d","dd");
        translate.put("D","MM/dd/yy");
        translate.put("e","dd"); //will show as '03' instead of ' 3'
        translate.put("F","yyyy-MM-dd");
        translate.put("g","yy");
        translate.put("G","yyyy");
        translate.put("H","HH");
        translate.put("h","MMM");
        translate.put("I","hh");
        translate.put("j","DDD");
        translate.put("k","HH"); //will show as '07' instead of ' 7'
        translate.put("l","hh"); //will show as '07' instead of ' 7'
        translate.put("m","MM");
        translate.put("M","mm");
        translate.put("n","\n");
        translate.put("p","a");
        translate.put("P","a");  //will show as pm instead of PM
        translate.put("r","hh:mm:ss a");
        translate.put("R","HH:mm");
        //There's no way to specify this with SimpleDateFormat
        //translate.put("s","seconds since epoch");
        translate.put("S","ss");
        translate.put("t","\t");
        translate.put("T","HH:mm:ss");
        //There's no way to specify this with SimpleDateFormat
        //translate.put("u","day of week ( 1-7 )");

        //There's no way to specify this with SimpleDateFormat
        //translate.put("U","week in year with first Sunday as first day...");

        translate.put("V","ww"); //I'm not sure this is always exactly the same

        //There's no way to specify this with SimpleDateFormat
        //translate.put("W","week in year with first Monday as first day...");

        //There's no way to specify this with SimpleDateFormat
        //translate.put("w","E");
        translate.put("X","HH:mm:ss");
        translate.put("x","MM/dd/yy");
        translate.put("y","yy");
        translate.put("Y","yyyy");
        translate.put("Z","z");
        translate.put("z","Z");
        translate.put("%","%");
    }


    
Create an instance of this date formatting class

Params:
  • origFormat – the strftime-style formatting string
  • locale – the locale to use for locale-specific conversions
/**
     * Create an instance of this date formatting class
     *
     * @param origFormat the strftime-style formatting string
     * @param locale the locale to use for locale-specific conversions
     */
    public Strftime( String origFormat, Locale locale ) {
        String convertedFormat = convertDateFormat( origFormat );
        simpleDateFormat = new SimpleDateFormat( convertedFormat, locale );
    }

    
Format the date according to the strftime-style string given in the constructor.

Params:
  • date – the date to format
Returns:the formatted date
/**
     * Format the date according to the strftime-style string given in the constructor.
     *
     * @param date the date to format
     * @return the formatted date
     */
    public String format( Date date ) {
        return simpleDateFormat.format( date );
    }

    
Get the timezone used for formatting conversions

Returns:the timezone
/**
     * Get the timezone used for formatting conversions
     *
     * @return the timezone
     */
    public TimeZone getTimeZone() {
        return simpleDateFormat.getTimeZone();
    }

    
Change the timezone used to format dates

Params:
  • timeZone – The new time zone
See Also:
/**
     * Change the timezone used to format dates
     *
     * @param timeZone The new time zone
     * @see SimpleDateFormat#setTimeZone
     */
    public void setTimeZone( TimeZone timeZone ) {
        simpleDateFormat.setTimeZone( timeZone );
    }

    
Search the provided pattern and get the C standard
Date/Time formatting rules and convert them to the
Java equivalent.

Params:
  • pattern – The pattern to search
Returns:The modified pattern
/**
     * Search the provided pattern and get the C standard
     * Date/Time formatting rules and convert them to the
     * Java equivalent.
     *
     * @param pattern The pattern to search
     * @return The modified pattern
     */
    protected String convertDateFormat( String pattern ) {
        boolean inside = false;
        boolean mark = false;
        boolean modifiedCommand = false;

        StringBuilder buf = new StringBuilder();

        for(int i = 0; i < pattern.length(); i++) {
            char c = pattern.charAt(i);

            if ( c=='%' && !mark ) {
                mark=true;
            } else {
                if ( mark ) {
                    if ( modifiedCommand ) {
                        //don't do anything--we just wanted to skip a char
                        modifiedCommand = false;
                        mark = false;
                    } else {
                        inside = translateCommand( buf, pattern, i, inside );
                        //It's a modifier code
                        if ( c=='O' || c=='E' ) {
                            modifiedCommand = true;
                        } else {
                            mark=false;
                        }
                    }
                } else {
                    if ( !inside && c != ' ' ) {
                        //We start a literal, which we need to quote
                        buf.append('\'');
                        inside = true;
                    }

                    buf.append(c);
                }
            }
        }

        if ( buf.length() > 0 ) {
            char lastChar = buf.charAt( buf.length() - 1 );

            if( lastChar!='\'' && inside ) {
                buf.append('\'');
            }
        }
        return buf.toString();
    }

    protected String quote( String str, boolean insideQuotes ) {
        String retVal = str;
        if ( !insideQuotes ) {
            retVal = '\'' + retVal + '\'';
        }
        return retVal;
    }

    
Try to get the Java Date/Time formatting associated with
the C standard provided.

Params:
  • buf – The buffer
  • pattern – The date/time pattern
  • index – The char index
  • oldInside – Flag value
Returns:True if new is inside buffer
/**
     * Try to get the Java Date/Time formatting associated with
     * the C standard provided.
     *
     * @param buf The buffer
     * @param pattern The date/time pattern
     * @param index The char index
     * @param oldInside Flag value
     * @return True if new is inside buffer
     */
    protected boolean translateCommand( StringBuilder buf, String pattern, int index, boolean oldInside ) {
        char firstChar = pattern.charAt( index );
        boolean newInside = oldInside;

        //O and E are modifiers, they mean to present an alternative representation of the next char
        //we just handle the next char as if the O or E wasn't there
        if ( firstChar == 'O' || firstChar == 'E' ) {
            if ( index + 1 < pattern.length() ) {
                newInside = translateCommand( buf, pattern, index + 1, oldInside );
            } else {
                buf.append( quote("%" + firstChar, oldInside ) );
            }
        } else {
            String command = translate.getProperty( String.valueOf( firstChar ) );

            //If we don't find a format, treat it as a literal--That's what apache does
            if ( command == null ) {
                buf.append( quote( "%" + firstChar, oldInside ) );
            } else {
                //If we were inside quotes, close the quotes
                if ( oldInside ) {
                    buf.append( '\'' );
                }
                buf.append( command );
                newInside = false;
            }
        }
        return newInside;
    }
}