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java/org/apache/el/util/Validation.java

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+/*
+ * 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;
+
+import java.security.AccessController;
+import java.security.PrivilegedAction;
+
+public class Validation {
+
+    // Java keywords, boolean literals & the null literal in alphabetical order
+    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 IS_SECURITY_ENABLED =
+            (System.getSecurityManager() != null);
+
+    private static final boolean SKIP_IDENTIFIER_CHECK;
+
+    static {
+        String skipIdentifierCheckStr;
+        if (IS_SECURITY_ENABLED) {
+            skipIdentifierCheckStr = AccessController.doPrivileged(
+                    new PrivilegedAction<String>(){
+                        @Override
+                        public String run() {
+                            return System.getProperty(
+                                    "org.apache.el.parser.SKIP_IDENTIFIER_CHECK",
+                                    "false");
+                        }
+                    }
+            );
+        } else {
+            skipIdentifierCheckStr = System.getProperty(
+                    "org.apache.el.parser.SKIP_IDENTIFIER_CHECK", "false");
+        }
+        SKIP_IDENTIFIER_CHECK = Boolean.parseBoolean(skipIdentifierCheckStr);
+    }
+
+
+    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.length() == 0) {
+            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;
+            }
+        }
+
+        // Check the start character that has more restrictions
+        if (!Character.isJavaIdentifierStart(key.charAt(0))) {
+            return false;
+        }
+
+        // Check each remaining character used is permitted
+        for (int idx = 1; idx < key.length(); idx++) {
+            if (!Character.isJavaIdentifierPart(key.charAt(idx))) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}