001    package org.apache.commons.ognl.enhance;
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.Node;
023    import org.apache.commons.ognl.OgnlContext;
024    
025    /**
026     * Provides pure java expression paths to get/set values from an ognl expression. This is achieved by taking an existing
027     * {@link Node} parsed expression and using bytecode enhancements to do the same work using pure java vs the ognl
028     * interpreter.
029     */
030    public interface ExpressionAccessor
031    {
032    
033        /**
034         * Gets the value represented by this expression path, if any.
035         * 
036         * @param context The standard ognl context used for variable substitution/etc.
037         * @param target The root object this expression is meant for.
038         * @return The evaluated value, if any.
039         */
040        Object get( OgnlContext context, Object target );
041    
042        /**
043         * Sets the value represented by this expression path, if possible.
044         * 
045         * @param context The standard ognl context used for variable substitution/etc.
046         * @param target The root object this expression is meant for.
047         * @param value The new value to set if this expression references a settable property.
048         */
049        void set( OgnlContext context, Object target, Object value );
050    
051        /**
052         * Used to set the original root expression node on instances where the compiled version has to fall back to
053         * interpreted syntax because of compilation failures.
054         * 
055         * @param expression The root expression node used to generate this accessor.
056         */
057        void setExpression( Node expression );
058    }