/*
* 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.el.util;
public class Validation {
/*
* Java keywords, boolean literals & the null literal in alphabetical order. As per the Java Language Specification,
* none of these are permitted to be used as an identifier.
*/
private static final String[] invalidIdentifiers = { "_", "abstract", "assert", "boolean", "break", "byte", "case",
"catch", "char", "class", "const", "continue", "default", "do", "double", "else", "enum", "extends",
"false", "final", "finally", "float", "for", "goto", "if", "implements", "import", "instanceof", "int",
"interface", "long", "native", "new", "null", "package", "private", "protected", "public", "return",
"short", "static", "strictfp", "super", "switch", "synchronized", "this", "throw", "throws", "transient",
"true", "try", "void", "volatile", "while" };
private static final boolean SKIP_IDENTIFIER_CHECK =
Boolean.getBoolean("org.apache.el.parser.SKIP_IDENTIFIER_CHECK");
private Validation() {
// Utility class. Hide default constructor
}
/**
* Test whether a string is a Java identifier. Note that the behaviour of this method depend on the system property
* {@code org.apache.el.parser.SKIP_IDENTIFIER_CHECK}
*
* @param key The string to test
*
* @return {@code true} if the provided String should be treated as a Java identifier, otherwise false
*/
public static boolean isIdentifier(String key) {
if (SKIP_IDENTIFIER_CHECK) {
return true;
}
// Should not be the case but check to be sure
if (key == null || key.isEmpty()) {
return false;
}
// Check the list of known invalid values
int i = 0;
int j = invalidIdentifiers.length;
while (i < j) {
int k = (i + j) >>> 1; // Avoid overflow
int result = invalidIdentifiers[k].compareTo(key);
if (result == 0) {
return false;
}
if (result < 0) {
i = k + 1;
} else {
j = k;
}
}
/*
* The parser checks Character.isJavaIdentifierStart() and Character.isJavaIdentifierPart() so no need to check
* them again here. However, we do need to check that '#' hasn't been used at the start of the identifier.
*/
return key.charAt(0) != '#';
}
}