api/src/main/java/javax/el/VariableMapper.java

/*
 * Copyright (c) 1997-2018 Oracle and/or its affiliates. All rights reserved.
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed 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 javax.el;

/**
 * The interface to a map between EL variables and the EL expressions
 * they are associated with.
 *
 * @since JSP 2.1
 */

public abstract class VariableMapper {
    
    /**
     * @param variable The variable name
     * @return the ValueExpression assigned to the variable,
     *         null if there is no previous assignment to this variable.
     */
    public abstract ValueExpression resolveVariable(
            String variable);
    
    /**
     * Assign a ValueExpression to an EL variable, replacing
     * any previously assignment to the same variable.
     * The assignment for the variable is removed if
     * the expression is <code>null</code>.
     *
     * @param variable The variable name
     * @param expression The ValueExpression to be assigned
     *        to the variable.
     * @return The previous ValueExpression assigned to this variable,
     *         null if there is no previous assignment to this variable.
     */
    public abstract ValueExpression setVariable(
            String variable,
            ValueExpression expression);
}