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.scxml;
018    
019    import java.util.Map;
020    
021    /**
022     * A Context or "scope" for storing variables; usually tied to
023     * a SCXML root or State object.
024     */
025    public interface Context {
026        /**
027         * Assigns a new value to an existing variable or creates a new one.
028         * The method searches the chain of parent Contexts for variable
029         * existence.
030         *
031         * @param name The variable name
032         * @param value The variable value
033         */
034        void set(String name, Object value);
035    
036        /**
037         * Assigns a new value to an existing variable or creates a new one.
038         * The method allows to shaddow a variable of the same name up the
039         * Context chain.
040         *
041         * @param name The variable name
042         * @param value The variable value
043         */
044        void setLocal(String name, Object value);
045    
046        /**
047         * Get the value of this variable; delegating to parent.
048         *
049         * @param name The name of the variable
050         * @return The value (or null)
051         */
052        Object get(String name);
053    
054        /**
055         * Check if this variable exists, delegating to parent.
056         *
057         * @param name The name of the variable
058         * @return Whether a variable with the name exists in this Context
059         */
060        boolean has(String name);
061    
062        /**
063         * Get the Map of all variables in this Context.
064         *
065         * @return Local variable entries Map
066         * To get variables in parent Context, call getParent().getVars().
067         * @see #getParent()
068         */
069        Map getVars();
070    
071        /**
072         * Clear this Context.
073         */
074        void reset();
075    
076        /**
077         * Get the parent Context, may be null.
078         *
079         * @return The parent Context in a chained Context environment
080         */
081        Context getParent();
082    
083    }