Escape SQL
/*
* Static String formatting and query routines.
* Copyright (C) 2001-2005 Stephen Ostermiller
* http://ostermiller.org/contact.pl?regarding=Java+Utilities
*
* 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; either version 2 of the License, or
* (at your option) any later version.
*
* 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.
*
* See COPYING.TXT for details.
*/
import java.util.HashMap;
import java.util.regex.Pattern;
/**
* Utilities for String formatting, manipulation, and queries.
* More information about this class is available from <a target="_top" href=
* "http://ostermiller.org/utils/StringHelper.html">ostermiller.org</a>.
*
* @author Stephen Ostermiller http://ostermiller.org/contact.pl?regarding=Java+Utilities
* @since ostermillerutils 1.00.00
*/
public class StringHelper {
/**
* Replaces characters that may be confused by an SQL
* parser with their equivalent escape characters.
* <p>
* Any data that will be put in an SQL query should
* be be escaped. This is especially important for data
* that comes from untrusted sources such as Internet users.
* <p>
* For example if you had the following SQL query:<br>
* <code>"SELECT * FROM addresses WHERE name='" + name + "' AND private='N'"</code><br>
* Without this function a user could give <code>" OR 1=1 OR ''='"</code>
* as their name causing the query to be:<br>
* <code>"SELECT * FROM addresses WHERE name='' OR 1=1 OR ''='' AND private='N'"</code><br>
* which will give all addresses, including private ones.<br>
* Correct usage would be:<br>
* <code>"SELECT * FROM addresses WHERE name='" + StringHelper.escapeSQL(name) + "' AND private='N'"</code><br>
* <p>
* Another way to avoid this problem is to use a PreparedStatement
* with appropriate placeholders.
*
* @param s String to be escaped
* @return escaped String
* @throws NullPointerException if s is null.
*
* @since ostermillerutils 1.00.00
*/
public static String escapeSQL(String s){
int length = s.length();
int newLength = length;
// first check for characters that might
// be dangerous and calculate a length
// of the string that has escapes.
for (int i=0; i<length; i++){
char c = s.charAt(i);
switch(c){
case '\\':
case '\"':
case '\'':
case '\0':{
newLength += 1;
} break;
}
}
if (length == newLength){
// nothing to escape in the string
return s;
}
StringBuffer sb = new StringBuffer(newLength);
for (int i=0; i<length; i++){
char c = s.charAt(i);
switch(c){
case '\\':{
sb.append("\\\\");
} break;
case '\"':{
sb.append("\\\"");
} break;
case '\'':{
sb.append("\\\'");
} break;
case '\0':{
sb.append("\\0");
} break;
default: {
sb.append(c);
}
}
}
return sb.toString();
}
}
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