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.util;
18
19 import org.apache.logging.log4j.util.Strings;
20
21
22 /**
23 * Utility class for transforming strings.
24 */
25 public final class Transform {
26
27 private static final String CDATA_START = "<![CDATA[";
28 private static final String CDATA_END = "]]>";
29 private static final String CDATA_PSEUDO_END = "]]>";
30 private static final String CDATA_EMBEDED_END = CDATA_END + CDATA_PSEUDO_END + CDATA_START;
31 private static final int CDATA_END_LEN = CDATA_END.length();
32
33 private Transform() {
34 }
35
36 /**
37 * This method takes a string which may contain HTML tags (ie,
38 * <b>, <table>, etc) and replaces any
39 * '<', '>' , '&' or '"'
40 * characters with respective predefined entity references.
41 *
42 * @param input The text to be converted.
43 * @return The input string with the special characters replaced.
44 */
45 public static String escapeHtmlTags(final String input) {
46 //Check if the string is null, zero length or devoid of special characters
47 // if so, return what was sent in.
48
49 if (Strings.isEmpty(input)
50 || (input.indexOf('"') == -1 &&
51 input.indexOf('&') == -1 &&
52 input.indexOf('<') == -1 &&
53 input.indexOf('>') == -1)) {
54 return input;
55 }
56
57 //Use a StringBuilder in lieu of String concatenation -- it is
58 //much more efficient this way.
59
60 final StringBuilder buf = new StringBuilder(input.length() + 6);
61 char ch = ' ';
62
63 final int len = input.length();
64 for (int i = 0; i < len; i++) {
65 ch = input.charAt(i);
66 if (ch > '>') {
67 buf.append(ch);
68 } else if (ch == '<') {
69 buf.append("<");
70 } else if (ch == '>') {
71 buf.append(">");
72 } else if (ch == '&') {
73 buf.append("&");
74 } else if (ch == '"') {
75 buf.append(""");
76 } else {
77 buf.append(ch);
78 }
79 }
80 return buf.toString();
81 }
82
83 /**
84 * Ensures that embedded CDEnd strings (]]>) are handled properly
85 * within message, NDC and throwable tag text.
86 *
87 * @param buf StringBuilder holding the XML data to this point. The
88 * initial CDStart (<![CDATA[) and final CDEnd (]]>) of the CDATA
89 * section are the responsibility of the calling method.
90 * @param str The String that is inserted into an existing CDATA Section within buf.
91 */
92 public static void appendEscapingCData(final StringBuilder buf, final String str) {
93 if (str != null) {
94 int end = str.indexOf(CDATA_END);
95 if (end < 0) {
96 buf.append(str);
97 } else {
98 int start = 0;
99 while (end > -1) {
100 buf.append(str.substring(start, end));
101 buf.append(CDATA_EMBEDED_END);
102 start = end + CDATA_END_LEN;
103 if (start < str.length()) {
104 end = str.indexOf(CDATA_END, start);
105 } else {
106 return;
107 }
108 }
109 buf.append(str.substring(start));
110 }
111 }
112 }
113
114 /**
115 * This method takes a string which may contain JSON reserved chars and
116 * escapes them.
117 *
118 * @param input The text to be converted.
119 * @return The input string with the special characters replaced.
120 */
121 public static String escapeJsonControlCharacters(final String input) {
122 // Check if the string is null, zero length or devoid of special characters
123 // if so, return what was sent in.
124
125 // TODO: escaped Unicode chars.
126
127 if (Strings.isEmpty(input)
128 || (input.indexOf('"') == -1 &&
129 input.indexOf('\\') == -1 &&
130 input.indexOf('/') == -1 &&
131 input.indexOf('\b') == -1 &&
132 input.indexOf('\f') == -1 &&
133 input.indexOf('\n') == -1 &&
134 input.indexOf('\r') == -1 &&
135 input.indexOf('\t') == -1)) {
136 return input;
137 }
138
139 final StringBuilder buf = new StringBuilder(input.length() + 6);
140
141 final int len = input.length();
142 for (int i = 0; i < len; i++) {
143 final char ch = input.charAt(i);
144 final String escBs = "\\";
145 switch (ch) {
146 case '"':
147 buf.append(escBs);
148 buf.append(ch);
149 break;
150 case '\\':
151 buf.append(escBs);
152 buf.append(ch);
153 break;
154 case '/':
155 buf.append(escBs);
156 buf.append(ch);
157 break;
158 case '\b':
159 buf.append(escBs);
160 buf.append('b');
161 break;
162 case '\f':
163 buf.append(escBs);
164 buf.append('f');
165 break;
166 case '\n':
167 buf.append(escBs);
168 buf.append('n');
169 break;
170 case '\r':
171 buf.append(escBs);
172 buf.append('r');
173 break;
174 case '\t':
175 buf.append(escBs);
176 buf.append('t');
177 break;
178 default:
179 buf.append(ch);
180 }
181 }
182 return buf.toString();
183 }
184 }