1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache license, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the license for the specific language governing permissions and
15 * limitations under the license.
16 */
17 package org.apache.logging.log4j.core.helpers;
18
19
20 /**
21 * Utility class for transforming strings.
22 */
23 public final class Transform {
24
25 private static final String CDATA_START = "<![CDATA[";
26 private static final String CDATA_END = "]]>";
27 private static final String CDATA_PSEUDO_END = "]]>";
28 private static final String CDATA_EMBEDED_END = CDATA_END + CDATA_PSEUDO_END + CDATA_START;
29 private static final int CDATA_END_LEN = CDATA_END.length();
30
31 private Transform() {
32 }
33
34 /**
35 * This method takes a string which may contain HTML tags (ie,
36 * <b>, <table>, etc) and replaces any
37 * '<', '>' , '&' or '"'
38 * characters with respective predefined entity references.
39 *
40 * @param input The text to be converted.
41 * @return The input string with the special characters replaced.
42 */
43 public static String escapeHtmlTags(final String input) {
44 //Check if the string is null, zero length or devoid of special characters
45 // if so, return what was sent in.
46
47 if (Strings.isEmpty(input)
48 || (input.indexOf('"') == -1 &&
49 input.indexOf('&') == -1 &&
50 input.indexOf('<') == -1 &&
51 input.indexOf('>') == -1)) {
52 return input;
53 }
54
55 //Use a StringBuilder in lieu of String concatenation -- it is
56 //much more efficient this way.
57
58 final StringBuilder buf = new StringBuilder(input.length() + 6);
59 char ch = ' ';
60
61 final int len = input.length();
62 for (int i = 0; i < len; i++) {
63 ch = input.charAt(i);
64 if (ch > '>') {
65 buf.append(ch);
66 } else if (ch == '<') {
67 buf.append("<");
68 } else if (ch == '>') {
69 buf.append(">");
70 } else if (ch == '&') {
71 buf.append("&");
72 } else if (ch == '"') {
73 buf.append(""");
74 } else {
75 buf.append(ch);
76 }
77 }
78 return buf.toString();
79 }
80
81 /**
82 * Ensures that embedded CDEnd strings (]]>) are handled properly
83 * within message, NDC and throwable tag text.
84 *
85 * @param buf StringBuilder holding the XML data to this point. The
86 * initial CDStart (<![CDATA[) and final CDEnd (]]>) of the CDATA
87 * section are the responsibility of the calling method.
88 * @param str The String that is inserted into an existing CDATA Section within buf.
89 */
90 public static void appendEscapingCDATA(final StringBuilder buf, final String str) {
91 if (str != null) {
92 int end = str.indexOf(CDATA_END);
93 if (end < 0) {
94 buf.append(str);
95 } else {
96 int start = 0;
97 while (end > -1) {
98 buf.append(str.substring(start, end));
99 buf.append(CDATA_EMBEDED_END);
100 start = end + CDATA_END_LEN;
101 if (start < str.length()) {
102 end = str.indexOf(CDATA_END, start);
103 } else {
104 return;
105 }
106 }
107 buf.append(str.substring(start));
108 }
109 }
110 }
111
112 /**
113 * This method takes a string which may contain JSON reserved chars and
114 * escapes them.
115 *
116 * @param input The text to be converted.
117 * @return The input string with the special characters replaced.
118 */
119 public static String escapeJsonControlCharacters(final String input) {
120 // Check if the string is null, zero length or devoid of special characters
121 // if so, return what was sent in.
122
123 // TODO: escaped Unicode chars.
124
125 if (Strings.isEmpty(input)
126 || (input.indexOf('"') == -1 &&
127 input.indexOf('\\') == -1 &&
128 input.indexOf('/') == -1 &&
129 input.indexOf('\b') == -1 &&
130 input.indexOf('\f') == -1 &&
131 input.indexOf('\n') == -1 &&
132 input.indexOf('\r') == -1 &&
133 input.indexOf('\t') == -1)) {
134 return input;
135 }
136
137 final StringBuilder buf = new StringBuilder(input.length() + 6);
138
139 final int len = input.length();
140 for (int i = 0; i < len; i++) {
141 final char ch = input.charAt(i);
142 final String escBs = "\\\\";
143 switch (ch) {
144 case '"':
145 buf.append(escBs);
146 buf.append(ch);
147 break;
148 case '\\':
149 buf.append(escBs);
150 buf.append(ch);
151 break;
152 case '/':
153 buf.append(escBs);
154 buf.append(ch);
155 break;
156 case '\b':
157 buf.append(escBs);
158 buf.append('b');
159 break;
160 case '\f':
161 buf.append(escBs);
162 buf.append('f');
163 break;
164 case '\n':
165 buf.append(escBs);
166 buf.append('n');
167 break;
168 case '\r':
169 buf.append(escBs);
170 buf.append('r');
171 break;
172 case '\t':
173 buf.append(escBs);
174 buf.append('t');
175 break;
176 default:
177 buf.append(ch);
178 }
179 }
180 return buf.toString();
181 }
182 }