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The Apache Log4j Implementation
/*
* 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
* limitations under the license.
*/
package org.apache.logging.log4j.core.util;
import org.apache.logging.log4j.util.Strings;
/**
* Utility class for transforming strings.
*/
public final class Transform {
private static final String CDATA_START = "";
private static final String CDATA_PSEUDO_END = "]]>";
private static final String CDATA_EMBEDED_END = CDATA_END + CDATA_PSEUDO_END + CDATA_START;
private static final int CDATA_END_LEN = CDATA_END.length();
private Transform() {
}
/**
* This method takes a string which may contain HTML tags (ie,
* <b>, <table>, etc) and replaces any
* '<', '>' , '&' or '"'
* characters with respective predefined entity references.
*
* @param input The text to be converted.
* @return The input string with the special characters replaced.
*/
public static String escapeHtmlTags(final String input) {
//Check if the string is null, zero length or devoid of special characters
// if so, return what was sent in.
if (Strings.isEmpty(input)
|| (input.indexOf('"') == -1 &&
input.indexOf('&') == -1 &&
input.indexOf('<') == -1 &&
input.indexOf('>') == -1)) {
return input;
}
//Use a StringBuilder in lieu of String concatenation -- it is
//much more efficient this way.
final StringBuilder buf = new StringBuilder(input.length() + 6);
final int len = input.length();
for (int i = 0; i < len; i++) {
final char ch = input.charAt(i);
if (ch > '>') {
buf.append(ch);
} else if (ch == '<') {
buf.append("<");
} else if (ch == '>') {
buf.append(">");
} else if (ch == '&') {
buf.append("&");
} else if (ch == '"') {
buf.append(""");
} else {
buf.append(ch);
}
}
return buf.toString();
}
/**
* Ensures that embedded CDEnd strings (]]>) are handled properly
* within message, NDC and throwable tag text.
*
* @param buf StringBuilder holding the XML data to this point. The
* initial CDStart (<![CDATA[) and final CDEnd (]]>) of the CDATA
* section are the responsibility of the calling method.
* @param str The String that is inserted into an existing CDATA Section within buf.
*/
public static void appendEscapingCData(final StringBuilder buf, final String str) {
if (str != null) {
int end = str.indexOf(CDATA_END);
if (end < 0) {
buf.append(str);
} else {
int start = 0;
while (end > -1) {
buf.append(str.substring(start, end));
buf.append(CDATA_EMBEDED_END);
start = end + CDATA_END_LEN;
if (start < str.length()) {
end = str.indexOf(CDATA_END, start);
} else {
return;
}
}
buf.append(str.substring(start));
}
}
}
/**
* This method takes a string which may contain JSON reserved chars and
* escapes them.
*
* @param input The text to be converted.
* @return The input string with the special characters replaced.
*/
public static String escapeJsonControlCharacters(final String input) {
// Check if the string is null, zero length or devoid of special characters
// if so, return what was sent in.
// TODO: escaped Unicode chars.
if (Strings.isEmpty(input)
|| (input.indexOf('"') == -1 &&
input.indexOf('\\') == -1 &&
input.indexOf('/') == -1 &&
input.indexOf('\b') == -1 &&
input.indexOf('\f') == -1 &&
input.indexOf('\n') == -1 &&
input.indexOf('\r') == -1 &&
input.indexOf('\t') == -1)) {
return input;
}
final StringBuilder buf = new StringBuilder(input.length() + 6);
final int len = input.length();
for (int i = 0; i < len; i++) {
final char ch = input.charAt(i);
final String escBs = "\\";
switch (ch) {
case '"':
buf.append(escBs);
buf.append(ch);
break;
case '\\':
buf.append(escBs);
buf.append(ch);
break;
case '/':
buf.append(escBs);
buf.append(ch);
break;
case '\b':
buf.append(escBs);
buf.append('b');
break;
case '\f':
buf.append(escBs);
buf.append('f');
break;
case '\n':
buf.append(escBs);
buf.append('n');
break;
case '\r':
buf.append(escBs);
buf.append('r');
break;
case '\t':
buf.append(escBs);
buf.append('t');
break;
default:
buf.append(ch);
}
}
return buf.toString();
}
}