src/java/org/apache/commons/jxpath/BasicVariables.java

/*
 * $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//jxpath/src/java/org/apache/commons/jxpath/BasicVariables.java,v 1.3 2002/05/08 23:02:42 dmitri Exp $
 * $Revision: 1.3 $
 * $Date: 2002/05/08 23:02:42 $
 *
 * ====================================================================
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999-2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was
 * originally based on software copyright (c) 2001, Plotnix, Inc,
 * <http://www.plotnix.com/>.
 * For more information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
package org.apache.commons.jxpath;

import java.util.HashMap;

/**
 * A basic implementation of the Variables interface that uses a HashMap.
 *
 * @author Dmitri Plotnikov
 * @version $Revision: 1.3 $ $Date: 2002/05/08 23:02:42 $
 */
public class BasicVariables implements Variables {

    /**
     * Contains the values of declared variables
     */
    private HashMap vars = new HashMap();

    /**
     * Returns true if the variable has been defined, even if the
     * value of the variable is null.
     *
     * @param varName is a variable name without the "$" sign
     *
     * @return true if the variable is declared
     */
    public boolean isDeclaredVariable(String varName){
        return vars.containsKey(varName);
    }

    /**
     * Returns the value of the variable if it is defined,
     * otherwise, throws IllegalArgumentException
     *
     * @param varName is a variable name without the "$" sign
     *
     * @return the value of the variable
     */
    public Object getVariable(String varName){
        // Note that a variable may be defined with a null value

        if (vars.containsKey(varName)){
            return vars.get(varName);
        }

        throw new IllegalArgumentException("No such variable: '" + varName + "'");
    }

    /**
     * Defines a new variable with the specified value or modifies
     * the value of an existing variable.
     *
     * @param varName is a variable name without the "$" sign
     * @param value is the new value for the variable, which can be null
     */
    public void declareVariable(String varName, Object value){
        vars.put(varName, value);
    }

    /**
     * Removes an existing variable. May throw UnsupportedOperationException.
     *
     * @param varName is a variable name without the "$" sign
     */
    public void undeclareVariable(String varName){
        vars.remove(varName);
    }
    public String toString(){
        return vars.toString();
    }
}