/**
* Copyright 2014 David L. Whitehurst
*
* Licensed 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 limitations under the
* License.
*
*/
package org.musicrecital.webapp.jsp;
/**
* Handles escaping of characters that could be interpreted as XML markup.
* <p>The specification for <code><c:out></code> defines the following
* character conversions to be applied:
* <table rules="all" frame="border">
* <tr><th>Character</th><th>Character Entity Code</th></tr>
* <tr><td><</td><td><</td></tr>
* <tr><td>></td><td>></td></tr>
* <tr><td>&</td><td>&</td></tr>
* <tr><td>'</td><td>'</td></tr>
* <tr><td>"</td><td>"</td></tr>
* </table>
*/
public class EscapeXml {
private static final String[] ESCAPES;
static {
int size = '>' + 1; // '>' is the largest escaped value
ESCAPES = new String[size];
ESCAPES['<'] = "<";
ESCAPES['>'] = ">";
ESCAPES['&'] = "&";
ESCAPES['\''] = "'";
ESCAPES['"'] = """;
}
private static String getEscape(char c) {
if (c < ESCAPES.length) {
return ESCAPES[c];
} else {
return null;
}
}
/**
* Escape a string.
*
* @param src
* the string to escape; must not be null
* @return the escaped string
*/
public static String escape(String src) {
// first pass to determine the length of the buffer so we only allocate once
int length = 0;
for (int i = 0; i < src.length(); i++) {
char c = src.charAt(i);
String escape = getEscape(c);
if (escape != null) {
length += escape.length();
} else {
length += 1;
}
}
// skip copy if no escaping is needed
if (length == src.length()) {
return src;
}
// second pass to build the escaped string
StringBuilder buf = new StringBuilder(length);
for (int i = 0; i < src.length(); i++) {
char c = src.charAt(i);
String escape = getEscape(c);
if (escape != null) {
buf.append(escape);
} else {
buf.append(c);
}
}
return buf.toString();
}
}