org.apache.axiom.util.xml.NSUtils Maven / Gradle / Ivy
/*
* 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.axiom.util.xml;
/**
* Contains utility methods to work with XML namespaces.
*/
public final class NSUtils {
private static final char[] prefixChars = new char[62];
static {
for (int i = 0; i < 10; i++) {
prefixChars[i] = (char)('0' + i);
}
for (int i = 0; i < 26; i++) {
prefixChars[i+10] = (char)('a' + i);
}
for (int i = 0; i < 26; i++) {
prefixChars[i+36] = (char)('A' + i);
}
}
private NSUtils() {}
/**
* Generate a namespace prefix for the given namespace URI. The generated prefix is based on a
* hash of the namespace URI. This implies that a given namespace URI is always mapped to the
* same prefix and that there is no guarantee that the generated prefixes are unique. However,
* the likelihood of a (accidental) collisions is very small.
*
* Using hash based prefixes has the advantage of reducing the number of entries created in the
* symbol table of the parser on the receiving side, assuming that the symbol table is reused to
* parse multiple documents (which is a common optimization).
*
* @param namespaceURI
* the namespace URI to generate a prefix for; must not be {@code null}
* @return the generated prefix
*/
public static String generatePrefix(String namespaceURI) {
char[] prefix = new char[7];
prefix[0] = 'n';
prefix[1] = 's';
int hash = namespaceURI.hashCode() & 0x7FFFFFFF;
for (int i = prefix.length-1; i >= 2; i--) {
prefix[i] = prefixChars[hash % 62];
hash /= 62;
}
return new String(prefix);
}
}