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BeanUtils provides an easy-to-use but flexible wrapper around reflection and introspection.
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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.beanutils.converters;


import java.io.IOException;
import java.io.StreamTokenizer;
import java.io.StringReader;
import java.util.ArrayList;
import java.util.List;
import org.apache.commons.beanutils.ConversionException;
import org.apache.commons.beanutils.Converter;



/**
 * Convenience base class for converters that translate the String
 * representation of an array into a corresponding array of primitives
 * object.  This class encapsulates the functionality required to parse
 * the String into a list of String elements that can later be
 * individually converted to the appropriate primitive type.
 *
 * The input syntax accepted by the parseElements() method
 * is designed to be compatible with the syntax used to initialize arrays
 * in a Java source program, except that only String literal values are
 * supported.  For maximum flexibility, the surrounding '{' and '}'
 * characters are optional, and individual elements may be separated by
 * any combination of whitespace and comma characters.
 *
 * @author Craig R. McClanahan
 * @version $Revision: 690380 $ $Date: 2008-08-29 16:04:38 -0400 (Fri, 29 Aug 2008) $
 * @since 1.4
 * @deprecated Replaced by the new {@link ArrayConverter} implementation
 */

public abstract class AbstractArrayConverter implements Converter {


    // ----------------------------------------------------------- Constructors


    /**
     * Create a {@link Converter} that will throw a {@link ConversionException}
     * if a conversion error occurs.
     */
    public AbstractArrayConverter() {

        this.defaultValue = null;
        this.useDefault = false;

    }

    /**
     * Create a {@link Converter} that will return the specified default value
     * if a conversion error occurs.
     *
     * @param defaultValue The default value to be returned
     * @since 1.8.0
     */
    public AbstractArrayConverter(Object defaultValue) {

        if (defaultValue == NO_DEFAULT) {
            this.useDefault = false;
        } else {
            this.defaultValue = defaultValue;
            this.useDefault = true;
        }

    }

    // ------------------------------------------------------- Static Variables

    /**
     * This is a special reference that can be passed as the "default object"
     * to the constructor to indicate that no default is desired. Note that
     * the value 'null' cannot be used for this purpose, as the caller may
     * want a null to be returned as the default.
     * @since 1.8.0
     */
    public static final Object NO_DEFAULT = new Object();

    // ----------------------------------------------------- Instance Variables


    /**
     * Model object for string arrays.
     */
    protected static String[] strings = new String[0];


    /**
     * The default value specified to our Constructor, if any.
     */
    protected Object defaultValue = null;


    /**
     * Should we return the default value on conversion errors?
     */
    protected boolean useDefault = true;


    // --------------------------------------------------------- Public Methods


    /**
     * Convert the specified input object into an output object of the
     * specified type.  This method must be implemented by a concrete
     * subclass.
     *
     * @param type Data type to which this value should be converted
     * @param value The input value to be converted
     * @return The converted value
     *
     * @exception ConversionException if conversion cannot be performed
     *  successfully
     */
    public abstract Object convert(Class type, Object value);


    // ------------------------------------------------------ Protected Methods


    /**
     * Parse an incoming String of the form similar to an array initializer
     * in the Java language into a List individual Strings
     * for each element, according to the following rules.
     * 
     * The string is expected to be a comma-separated list of values.
     * The string may optionally have matching '{' and '}' delimiters
     *   around the list.
     * Whitespace before and after each element is stripped.
     * Elements in the list may be delimited by single or double quotes.
     *  Within a quoted elements, the normal Java escape sequences are valid.
     * 
     *
     * @param svalue String value to be parsed
     * @return The parsed list of String values
     *
     * @exception ConversionException if the syntax of svalue
     *  is not syntactically valid
     * @exception NullPointerException if svalue
     *  is null
     */
    protected List parseElements(String svalue) {

        // Validate the passed argument
        if (svalue == null) {
            throw new NullPointerException();
        }

        // Trim any matching '{' and '}' delimiters
        svalue = svalue.trim();
        if (svalue.startsWith("{") && svalue.endsWith("}")) {
            svalue = svalue.substring(1, svalue.length() - 1);
        }

        try {

            // Set up a StreamTokenizer on the characters in this String
            StreamTokenizer st =
                new StreamTokenizer(new StringReader(svalue));
            st.whitespaceChars(',',','); // Commas are delimiters
            st.ordinaryChars('0', '9');  // Needed to turn off numeric flag
            st.ordinaryChars('.', '.');
            st.ordinaryChars('-', '-');
            st.wordChars('0', '9');      // Needed to make part of tokens
            st.wordChars('.', '.');
            st.wordChars('-', '-');

            // Split comma-delimited tokens into a List
            ArrayList list = new ArrayList();
            while (true) {
                int ttype = st.nextToken();
                if ((ttype == StreamTokenizer.TT_WORD) ||
                    (ttype > 0)) {
                    list.add(st.sval);
                } else if (ttype == StreamTokenizer.TT_EOF) {
                    break;
                } else {
                    throw new ConversionException
                        ("Encountered token of type " + ttype);
                }
            }

            // Return the completed list
            return (list);

        } catch (IOException e) {

            throw new ConversionException(e);

        }



    }


}