BooleanConverter.java

/**
 * $Id: BooleanConverter.java 2 2008-10-01 10:04:26Z azeckoski $
 * $URL: http://reflectutils.googlecode.com/svn/trunk/src/main/java/org/azeckoski/reflectutils/converters/BooleanConverter.java $
 * BooleanConverter.java - genericdao - Sep 8, 2008 11:42:27 AM - azeckoski
 **************************************************************************
 * Copyright (c) 2008 Aaron Zeckoski
 * Licensed under the Apache License, Version 2.0
 * 
 * A copy of the Apache License has been included in this 
 * distribution and is available at: http://www.apache.org/licenses/LICENSE-2.0.txt
 *
 * Aaron Zeckoski (azeckoski @ gmail.com) (aaronz @ vt.edu) (aaron @ caret.cam.ac.uk)
 */

package org.azeckoski.reflectutils.converters;

import org.azeckoski.reflectutils.ConversionUtils;
import org.azeckoski.reflectutils.converters.api.Converter;


/**
 * Converts objects into booleans (by default this will return Boolean.FALSE)<br/>
 * Special handling:<br/>
 * Numerics greater than 0 are true, less than or equal are false <br/>
 * 
 * <p>Case is ignored when converting values to true or false.</p>
 * <br/>
 * Based on code from commons bean utils but updated for generics and removed complexity and (mis)usage of Throwable<br/>
 * 
 * @author Aaron Zeckoski (azeckoski @ gmail.com)
 */
public class BooleanConverter implements Converter<Boolean> {

    public Boolean convert(Object value) {

        Boolean converted = null;
        if (value instanceof Number) {
            // numbers
            if (((Number)value).intValue() > 0) {
                converted = Boolean.TRUE;
            } else {
                converted = Boolean.FALSE;
            }
        } else {
            // strings and all others
            String stringValue = value.toString();
            if (stringValue != null) {
                stringValue = stringValue.toLowerCase();
                if ("0".equals(stringValue) || "".equals(stringValue)) {
                    converted = Boolean.FALSE;
                } else if ("1".equals(stringValue)) {
                    converted = Boolean.TRUE;
                } else {
                    for (int i=0; i<trueStrings.length; ++i) {
                        if (trueStrings[i].equals(stringValue)) {
                            converted = Boolean.TRUE;
                        }
                    }
                    for (int i=0; i<falseStrings.length; ++i) {
                        if (falseStrings[i].equals(stringValue)) {
                            converted = Boolean.FALSE;
                        }
                    }
                }
            }
        }

        if (converted == null) {
            throw new UnsupportedOperationException("Boolean conversion exception: Cannot convert ("+value+") of type ("+value.getClass()+") into boolean");
        }
        return converted;
    }

    // code derived form the commons beanutils converters

    /**
     * The set of strings that are known to map to Boolean.TRUE.
     */
    private String[] trueStrings = {"true", "yes", "y", "on"};

    /**
     * The set of strings that are known to map to Boolean.FALSE.
     */
    private String[] falseStrings = {"false", "no", "n", "off"};


    public BooleanConverter() { }

    /**
     * Allows the false strings and true strings to be controlled<br/>
     * By default any object whose string representation is one of the values
     * {"yes", "y", "true", "on", "1"} is converted to Boolean.TRUE, and 
     * string representations {"no", "n", "false", "off", "0"} are converted
     * to Boolean.FALSE. The recognised true/false strings can be changed using the constructor
     * in this class and registering it with the {@link ConversionUtils}:
     * <pre>
     *  String[] trueStrings = {"oui", "o"};
     *  String[] falseStrings = {"non", "n"};
     *  Converter bc = new BooleanConverter(trueStrings, falseStrings);
     * </pre>
     * @param trueStrings these strings map to true
     * @param falseStrings these strings map to false
     */
    public BooleanConverter(String[] trueStrings, String[] falseStrings) {
        this.falseStrings = copyStrings(falseStrings);
        this.trueStrings = copyStrings(trueStrings);
    }

    /**
     * This method creates a copy of the provided array, and ensures that
     * all the strings in the newly created array contain only lower-case
     * letters.
     * <p>
     * Using this method to copy string arrays means that changes to the
     * src array do not modify the dst array.
     */
    private static String[] copyStrings(String[] src) {
        String[] dst = new String[src.length];
        for(int i=0; i<src.length; ++i) {
            dst[i] = src[i].toLowerCase();
        }
        return dst;
    }

}