Utility methods for dealing with HTML
/* Copyright 2005-2006 Tim Fennell
*
* 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.
*/
// sourceforge stripes
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.regex.Pattern;
/**
* Provides simple utility methods for dealing with HTML.
*
* @author Tim Fennell
*/
public class HtmlUtil {
private static final String FIELD_DELIMITER_STRING = "||";
private static final Pattern FIELD_DELIMITER_PATTERN = Pattern.compile("\\|\\|");
/**
* Replaces special HTML characters from the set {@literal [<, >, ", ', &]} with their HTML
* escape codes. Note that because the escape codes are multi-character that the returned
* String could be longer than the one passed in.
*
* @param fragment a String fragment that might have HTML special characters in it
* @return the fragment with special characters escaped
*/
public static String encode(String fragment) {
// If the input is null, then the output is null
if (fragment == null) return null;
StringBuilder builder = new StringBuilder(fragment.length() + 10); // a little wiggle room
char[] characters = fragment.toCharArray();
// This loop used to also look for and replace single ticks with ' but it
// turns out that it's not strictly necessary since Stripes uses double-quotes
// around all form fields, and stupid IE6 will render ' verbatim instead
// of as a single quote.
for (int i=0; i<characters.length; ++i) {
switch (characters[i]) {
case '<' : builder.append("<"); break;
case '>' : builder.append(">"); break;
case '"' : builder.append("""); break;
case '&' : builder.append("&"); break;
default: builder.append(characters[i]);
}
}
return builder.toString();
}
/**
* One of a pair of methods (the other is splitValues) that is used to combine several
* un-encoded values into a single delimited, encoded value for placement into a
* hidden field.
*
* @param values One or more values which are to be combined
* @return a single HTML-encoded String that contains all the values in such a way that
* they can be converted back into a Collection of Strings with splitValues().
*/
public static String combineValues(Collection<String> values) {
if (values == null || values.size() == 0) {
return "";
}
else {
StringBuilder builder = new StringBuilder(values.size() * 30);
for (String value : values) {
builder.append(value).append(FIELD_DELIMITER_STRING);
}
return encode(builder.toString());
}
}
/**
* Takes in a String produced by combineValues and returns a Collection of values that
* contains the same values as originally supplied to combineValues. Note that the order
* or items in the collection (and indeed the type of Collection used) are not guaranteed
* to be the same.
*
* @param value a String value produced by
* @return a Collection of zero or more Strings
*/
public static Collection<String> splitValues(String value) {
if (value == null || value.length() == 0) {
return Collections.emptyList();
}
else {
String[] splits = FIELD_DELIMITER_PATTERN.split(value);
return Arrays.asList(splits);
}
}
}
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