001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.jexl2.parser;
018    
019    import org.apache.commons.jexl2.DebugInfo;
020    import org.apache.commons.jexl2.JexlInfo;
021    
022    /**
023     * Base class for parser nodes - holds an 'image' of the token for later use.
024     *
025     * @since 2.0
026     */
027    public abstract class JexlNode extends SimpleNode implements JexlInfo {
028        /** A marker interface for literals.
029         * @param <T> the literal type
030         */
031        public interface Literal<T> {
032            T getLiteral();
033        }
034        /** token value. */
035        public String image;
036    
037        public JexlNode(int id) {
038            super(id);
039        }
040    
041        public JexlNode(Parser p, int id) {
042            super(p, id);
043        }
044    
045        /** {@inheritDoc} */
046        public DebugInfo debugInfo() {
047            JexlNode node = this;
048            while (node != null) {
049                if (node.value instanceof DebugInfo) {
050                    return (DebugInfo) node.value;
051                }
052                node = node.jjtGetParent();
053            }
054            return null;
055        }
056    
057        /** {@inheritDoc} */
058        public String debugString() {
059            DebugInfo info = debugInfo();
060            return info != null ? info.debugString() : "";
061        }
062    
063        /**
064         * Whether this node is a constant node
065         * Its value can not change after the first evaluation and can be cached indefinitely.
066         * @return true if constant, false otherwise
067         */
068        public final boolean isConstant() {
069            return isConstant(this instanceof JexlNode.Literal<?>);
070        }
071    
072        protected boolean isConstant(boolean literal) {
073            if (literal) {
074                if (children != null) {
075                    for (JexlNode child : children) {
076                        if (child instanceof ASTReference) {
077                            boolean is = child.isConstant(true);
078                            if (!is) {
079                                return false;
080                            }
081                        } else if (child instanceof ASTMapEntry) {
082                            boolean is = child.isConstant(true);
083                            if (!is) {
084                                return false;
085                            }
086                        } else if (!child.isConstant()) {
087                            return false;
088                        }
089                    }
090                }
091                return true;
092            }
093            return false;
094        }
095    }