Java String Unquote unQuoteIdentifier(String identifier, String quoteChar)

Description

Trims identifier, removes quote chars from first and last positions and replaces double occurrences of quote char from entire identifier, i.e converts quoted identifier into form as it is stored in database.

License

Open Source License

Parameter

Parameter	Description
identifier	a parameter
quoteChar	` or "

Return

null -> null
abc -> abc
`abc` -> abc
`ab``c` -> ab`c
`"ab`c"` -> "ab`c"
`ab"c` -> ab"c
"abc" -> abc
"`ab""c`" -> `ab"c`
"ab`c" -> ab`c

Declaration

public static String unQuoteIdentifier(String identifier, String quoteChar)

Method Source Code

//package com.java2s;
/*/*from w  ww.  j av a  2 s  . co m*/
  Copyright (c) 2002, 2016, Oracle and/or its affiliates. All rights reserved.
    
  The MySQL Connector/J is licensed under the terms of the GPLv2
  <http://www.gnu.org/licenses/old-licenses/gpl-2.0.html>, like most MySQL Connectors.
  There are special exceptions to the terms and conditions of the GPLv2 as it is applied to
  this software, see the FOSS License Exception
  <http://www.mysql.com/about/legal/licensing/foss-exception.html>.
    
  This program is free software; you can redistribute it and/or modify it under the terms
  of the GNU General Public License as published by the Free Software Foundation; version 2
  of the License.
    
  This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
  without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  See the GNU General Public License for more details.
    
  You should have received a copy of the GNU General Public License along with this
  program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth
  Floor, Boston, MA 02110-1301  USA
    
 */

public class Main {
    /**
     * Trims identifier, removes quote chars from first and last positions
     * and replaces double occurrences of quote char from entire identifier,
     * i.e converts quoted identifier into form as it is stored in database.
     * 
     * @param identifier
     * @param quoteChar
     *            ` or "
     * @return
     *         <ul>
     *         <li>null {@code ->} null</li>
     *         <li>abc {@code ->} abc</li>
     *         <li>`abc` {@code ->} abc</li>
     *         <li>`ab``c` {@code ->} ab`c</li>
     *         <li>`"ab`c"` {@code ->} "ab`c"</li>
     *         <li>`ab"c` {@code ->} ab"c</li>
     *         <li>"abc" {@code ->} abc</li>
     *         <li>"`ab""c`" {@code ->} `ab"c`</li>
     *         <li>"ab`c" {@code ->} ab`c</li>
     *         </ul>
     */
    public static String unQuoteIdentifier(String identifier, String quoteChar) {
        if (identifier == null) {
            return null;
        }

        identifier = identifier.trim();

        int quoteCharLength = quoteChar.length();
        if (quoteCharLength == 0) {
            return identifier;
        }

        // Check if the identifier is really quoted or if it simply contains quote chars in it (assuming that the value is a valid identifier).
        if (identifier.startsWith(quoteChar) && identifier.endsWith(quoteChar)) {
            // Trim outermost quotes from the identifier.
            String identifierQuoteTrimmed = identifier.substring(quoteCharLength,
                    identifier.length() - quoteCharLength);

            // Check for pairs of quotes.
            int quoteCharPos = identifierQuoteTrimmed.indexOf(quoteChar);
            while (quoteCharPos >= 0) {
                int quoteCharNextExpectedPos = quoteCharPos + quoteCharLength;
                int quoteCharNextPosition = identifierQuoteTrimmed.indexOf(quoteChar, quoteCharNextExpectedPos);

                if (quoteCharNextPosition == quoteCharNextExpectedPos) {
                    quoteCharPos = identifierQuoteTrimmed.indexOf(quoteChar,
                            quoteCharNextPosition + quoteCharLength);
                } else {
                    // Not a pair of quotes! Return as it is...
                    return identifier;
                }
            }

            return identifier.substring(quoteCharLength, (identifier.length() - quoteCharLength))
                    .replaceAll(quoteChar + quoteChar, quoteChar);
        }

        return identifier;
    }

    private static boolean startsWith(byte[] dataFrom, String chars) {
        int charsLength = chars.length();

        if (dataFrom.length < charsLength) {
            return false;
        }
        for (int i = 0; i < charsLength; i++) {
            if (dataFrom[i] != chars.charAt(i)) {
                return false;
            }
        }
        return true;
    }

    private static boolean endsWith(byte[] dataFrom, String suffix) {
        for (int i = 1; i <= suffix.length(); i++) {
            int dfOffset = dataFrom.length - i;
            int suffixOffset = suffix.length() - i;
            if (dataFrom[dfOffset] != suffix.charAt(suffixOffset)) {
                return false;
            }
        }
        return true;
    }

    public static int indexOf(byte[] s, char c) {
        if (s == null) {
            return -1;
        }

        int length = s.length;

        for (int i = 0; i < length; i++) {
            if (s[i] == c) {
                return i;
            }
        }

        return -1;
    }
}