001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache license, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the license for the specific language governing permissions and 015 * limitations under the license. 016 */ 017 package org.apache.logging.log4j.core.helpers; 018 019 020 /** 021 * Utility class for transforming strings. 022 */ 023 public final class Transform { 024 025 private static final String CDATA_START = "<![CDATA["; 026 private static final String CDATA_END = "]]>"; 027 private static final String CDATA_PSEUDO_END = "]]>"; 028 private static final String CDATA_EMBEDED_END = CDATA_END + CDATA_PSEUDO_END + CDATA_START; 029 private static final int CDATA_END_LEN = CDATA_END.length(); 030 031 private Transform() { 032 } 033 034 /** 035 * This method takes a string which may contain HTML tags (ie, 036 * <b>, <table>, etc) and replaces any 037 * '<', '>' , '&' or '"' 038 * characters with respective predefined entity references. 039 * 040 * @param input The text to be converted. 041 * @return The input string with the special characters replaced. 042 */ 043 public static String escapeTags(final String input) { 044 //Check if the string is null, zero length or devoid of special characters 045 // if so, return what was sent in. 046 047 if (input == null 048 || input.length() == 0 049 || (input.indexOf('"') == -1 && 050 input.indexOf('&') == -1 && 051 input.indexOf('<') == -1 && 052 input.indexOf('>') == -1)) { 053 return input; 054 } 055 056 //Use a StringBuffer in lieu of String concatenation -- it is 057 //much more efficient this way. 058 059 final StringBuilder buf = new StringBuilder(input.length() + 6); 060 char ch = ' '; 061 062 final int len = input.length(); 063 for (int i = 0; i < len; i++) { 064 ch = input.charAt(i); 065 if (ch > '>') { 066 buf.append(ch); 067 } else if (ch == '<') { 068 buf.append("<"); 069 } else if (ch == '>') { 070 buf.append(">"); 071 } else if (ch == '&') { 072 buf.append("&"); 073 } else if (ch == '"') { 074 buf.append("""); 075 } else { 076 buf.append(ch); 077 } 078 } 079 return buf.toString(); 080 } 081 082 /** 083 * Ensures that embedded CDEnd strings (]]>) are handled properly 084 * within message, NDC and throwable tag text. 085 * 086 * @param buf StringBuffer holding the XML data to this point. The 087 * initial CDStart (<![CDATA[) and final CDEnd (]]>) of the CDATA 088 * section are the responsibility of the calling method. 089 * @param str The String that is inserted into an existing CDATA Section within buf. 090 */ 091 public static void appendEscapingCDATA(final StringBuilder buf, final String str) { 092 if (str != null) { 093 int end = str.indexOf(CDATA_END); 094 if (end < 0) { 095 buf.append(str); 096 } else { 097 int start = 0; 098 while (end > -1) { 099 buf.append(str.substring(start, end)); 100 buf.append(CDATA_EMBEDED_END); 101 start = end + CDATA_END_LEN; 102 if (start < str.length()) { 103 end = str.indexOf(CDATA_END, start); 104 } else { 105 return; 106 } 107 } 108 buf.append(str.substring(start)); 109 } 110 } 111 } 112 }