Commons Beanutils example source code file (AbstractArrayConverter.java)

This example Commons Beanutils source code file (AbstractArrayConverter.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons Beanutils tags/keywords

abstractarrayconverter, abstractarrayconverter, arraylist, commas, conversionexception, io, needed, no_default, no_default, object, object, streamtokenizer, string, string, stringreader, util

The Commons Beanutils AbstractArrayConverter.java source code

/*
 * 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;



/**
 * <p>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.</p>
 *
 * <p>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.</p>
 *
 * @author Craig R. McClanahan
 * @version $Revision: 690380 $ $Date: 2008-08-29 21:04:38 +0100 (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


    /**
     * <p>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


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

        }



    }


}