001 package org.apache.commons.ognl;
002
003 /*
004 * Licensed to the Apache Software Foundation (ASF) under one
005 * or more contributor license agreements. See the NOTICE file
006 * distributed with this work for additional information
007 * regarding copyright ownership. The ASF licenses this file
008 * to you under the Apache License, Version 2.0 (the
009 * "License"); you may not use this file except in compliance
010 * with the License. You may obtain a copy of the License at
011 *
012 * http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing,
015 * software distributed under the License is distributed on an
016 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
017 * KIND, either express or implied. See the License for the
018 * specific language governing permissions and limitations
019 * under the License.
020 */
021
022 import org.apache.commons.ognl.enhance.ExpressionAccessor;
023
024 /**
025 * JJTree interface for AST nodes, as modified to handle the OGNL operations getValue and setValue. JJTree's original
026 * comment: All AST nodes must implement this interface. It provides basic machinery for constructing the parent and
027 * child relationships between nodes.
028 *
029 * @author Luke Blanshard (blanshlu@netscape.net)
030 * @author Drew Davidson (drew@ognl.org)
031 */
032 public interface Node
033 extends JavaSource
034 {
035
036 /**
037 * This method is called after the node has been made the current node. It indicates that child nodes can now be
038 * added to it.
039 */
040 void jjtOpen();
041
042 /**
043 * This method is called after all the child nodes have been added.
044 */
045 void jjtClose();
046
047 /**
048 * This pair of methods are used to inform the node of its parent.
049 */
050 void jjtSetParent( Node n );
051
052 Node jjtGetParent();
053
054 /**
055 * This method tells the node to add its argument to the node's list of children.
056 */
057 void jjtAddChild( Node n, int i );
058
059 /**
060 * This method returns a child node. The children are numbered from zero, left to right.
061 */
062 Node jjtGetChild( int i );
063
064 /** Return the number of children the node has. */
065 int jjtGetNumChildren();
066
067 // OGNL additions to Node:
068
069 /**
070 * Extracts the value from the given source object that is appropriate for this node within the given context.
071 */
072 Object getValue( OgnlContext context, Object source )
073 throws OgnlException;
074
075 /**
076 * Sets the given value in the given target as appropriate for this node within the given context.
077 */
078 void setValue( OgnlContext context, Object target, Object value )
079 throws OgnlException;
080
081 /**
082 * Gets the compiled bytecode enhanced expression accessor for getting/setting values.
083 *
084 * @return The accessor for this node, or null if none has been compiled for it.
085 */
086 ExpressionAccessor getAccessor();
087
088 /**
089 * Sets a new compiled accessor for this node expression.
090 *
091 * @param accessor The compiled representation of this node.
092 */
093 void setAccessor( ExpressionAccessor accessor );
094
095
096 /**
097 * Supports the Visitor pattern. The method which corresponds to
098 * the runtime type of this Node will be called.
099 *
100 * @param visitor The visitor to accept.
101 * @param data The second parameter to pass through to visitor.visit
102 * @param <R> The return type of the visitor.visit method.
103 * @param <P> The type of the second parameter type.
104 * @return the value returned by visitor.visit
105 * @throws NullPointerException if visitor is null
106 * @throws RuntimeException if visitor.visit throws an exception.
107 */
108 <R, P> R accept( NodeVisitor<? extends R, ? super P> visitor, P data )
109 throws OgnlException;
110
111 }