org.springframework.security.web.util.TextEscapeUtils Maven / Gradle / Ivy
/*
* Copyright 2002-2016 the original author or authors.
*
* 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.springframework.security.web.util;
/**
* Internal utility for escaping characters in HTML strings.
*
* @author Luke Taylor
*
*/
public abstract class TextEscapeUtils {
public static String escapeEntities(String s) {
if (s == null || s.length() == 0) {
return s;
}
StringBuilder sb = new StringBuilder();
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
if (c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9') {
sb.append(c);
}
else if (c == '<') {
sb.append("<");
}
else if (c == '>') {
sb.append(">");
}
else if (c == '&') {
sb.append("&");
}
else if (Character.isWhitespace(c)) {
sb.append("&#").append((int) c).append(";");
}
else if (Character.isISOControl(c)) {
// ignore control chars
}
else if (Character.isHighSurrogate(c)) {
if (i + 1 >= s.length()) {
// Unexpected end
throw new IllegalArgumentException(
"Missing low surrogate character at end of string");
}
char low = s.charAt(i + 1);
if (!Character.isLowSurrogate(low)) {
throw new IllegalArgumentException(
"Expected low surrogate character but found value = "
+ (int) low);
}
int codePoint = Character.toCodePoint(c, low);
if (Character.isDefined(codePoint)) {
sb.append("&#").append(codePoint).append(";");
}
i++; // skip the next character as we have already dealt with it
}
else if (Character.isLowSurrogate(c)) {
throw new IllegalArgumentException(
"Unexpected low surrogate character, value = " + (int) c);
}
else if (Character.isDefined(c)) {
sb.append("&#").append((int) c).append(";");
}
// Ignore anything else
}
return sb.toString();
}
}