    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.beanutils.converters;
    018
    019/**
    020 * {@link org.apache.commons.beanutils.Converter} implementation that handles conversion
    021 * to and from <strong>Boolean</strong> objects.
    022 * {@link org.apache.commons.beanutils.Converter} implementation that
    023 * handles conversion to and from <strong>java.lang.Boolean</strong> objects.
    024 * <p>
    025 * Can be configured to either return a <em>default value</em> or throw a
    026 * <code>ConversionException</code> if a conversion error occurs.
    027 * </p>
    028 * <p>
    029 * By default any object whose string representation is one of the values
    030 * {"yes", "y", "true", "on", "1"} is converted to Boolean.TRUE, and
    031 * string representations {"no", "n", "false", "off", "0"} are converted
    032 * to Boolean.FALSE. The recognized true/false strings can be changed by:
    033 * </p>
    034 * <pre>
    035 *  String[] trueStrings = {"oui", "o", "1"};
    036 *  String[] falseStrings = {"non", "n", "0"};
    037 *  Converter bc = new BooleanConverter(trueStrings, falseStrings);
    038 *  ConvertUtils.register(bc, Boolean.class);
    039 *  ConvertUtils.register(bc, Boolean.TYPE);
    040 * </pre>
    041 * <p>
    042 * In addition, it is recommended that the BooleanArrayConverter also be
    043 * modified to recognise the same set of values:
    044 * </p>
    045 * <pre>
    046 *   Converter bac = new BooleanArrayConverter(bc, BooleanArrayConverter.NO_DEFAULT);
    047 *   ConvertUtils.register(bac, bac.MODEL);
    048 * </pre>
    049 * <p>Case is ignored when converting values to true or false.</p>
    050 *
    051 * @since 1.3
    052 */
    053public final class BooleanConverter extends AbstractConverter {
    054
    055    /**
    056     * This is a special reference that can be passed as the "default object"
    057     * to the constructor to indicate that no default is desired. Note that
    058     * the value 'null' cannot be used for this purpose, as the caller may
    059     * want a null to be returned as the default.
    060     * @deprecated Use constructors without default value.
    061     */
    062    @Deprecated
    063    public static final Object NO_DEFAULT = new Object();
    064
    065    /**
    066     * This method creates a copy of the provided array, and ensures that
    067     * all the strings in the newly created array contain only lower-case
    068     * letters.
    069     * <p>
    070     * Using this method to copy string arrays means that changes to the
    071     * src array do not modify the dst array.
    072     */
    073    private static String[] copyStrings(final String[] src) {
    074        final String[] dst = new String[src.length];
    075        for(int i=0; i<src.length; ++i) {
    076            dst[i] = src[i].toLowerCase();
    077        }
    078        return dst;
    079    }
    080
    081    /**
    082     * The set of strings that are known to map to Boolean.TRUE.
    083     */
    084    private String[] trueStrings = {"true", "yes", "y", "on", "1"};
    085
    086    /**
    087     * The set of strings that are known to map to Boolean.FALSE.
    088     */
    089    private String[] falseStrings = {"false", "no", "n", "off", "0"};
    090
    091    /**
    092     * Create a {@link org.apache.commons.beanutils.Converter} that will throw a
    093     * {@link org.apache.commons.beanutils.ConversionException}
    094     * if a conversion error occurs, ie the string value being converted is
    095     * not one of the known true strings, nor one of the known false strings.
    096     */
    097    public BooleanConverter() {
    098    }
    099
    100    /**
    101     * Create a {@link org.apache.commons.beanutils.Converter} that will return the specified default value
    102     * if a conversion error occurs, ie the string value being converted is
    103     * not one of the known true strings, nor one of the known false strings.
    104     *
    105     * @param defaultValue The default value to be returned if the value
    106     *  being converted is not recognized. This value may be null, in which
    107     *  case null will be returned on conversion failure. When non-null, it is
    108     *  expected that this value will be either Boolean.TRUE or Boolean.FALSE.
    109     *  The special value BooleanConverter.NO_DEFAULT can also be passed here,
    110     *  in which case this constructor acts like the no-argument one.
    111     */
    112    public BooleanConverter(final Object defaultValue) {
    113        if (defaultValue != NO_DEFAULT) {
    114            setDefaultValue(defaultValue);
    115        }
    116    }
    117
    118    /**
    119     * Create a {@link org.apache.commons.beanutils.Converter} that will throw a
    120     * {@link org.apache.commons.beanutils.ConversionException}
    121     * if a conversion error occurs, ie the string value being converted is
    122     * not one of the known true strings, nor one of the known false strings.
    123     * <p>
    124     * The provided string arrays are copied, so that changes to the elements
    125     * of the array after this call is made do not affect this object.
    126     *
    127     * @param trueStrings is the set of strings which should convert to the
    128     *  value Boolean.TRUE. The value null must not be present. Case is
    129     *  ignored.
    130     *
    131     * @param falseStrings is the set of strings which should convert to the
    132     *  value Boolean.TRUE. The value null must not be present. Case is
    133     *  ignored.
    134     * @since 1.8.0
    135     */
    136    public BooleanConverter(final String[] trueStrings, final String[] falseStrings) {
    137        this.trueStrings = copyStrings(trueStrings);
    138        this.falseStrings = copyStrings(falseStrings);
    139    }
    140
    141    /**
    142     * Create a {@link org.apache.commons.beanutils.Converter} that will return
    143     * the specified default value if a conversion error occurs.
    144     * <p>
    145     * The provided string arrays are copied, so that changes to the elements
    146     * of the array after this call is made do not affect this object.
    147     *
    148     * @param trueStrings is the set of strings which should convert to the
    149     *  value Boolean.TRUE. The value null must not be present. Case is
    150     *  ignored.
    151     *
    152     * @param falseStrings is the set of strings which should convert to the
    153     *  value Boolean.TRUE. The value null must not be present. Case is
    154     *  ignored.
    155     *
    156     * @param defaultValue The default value to be returned if the value
    157     *  being converted is not recognized. This value may be null, in which
    158     *  case null will be returned on conversion failure. When non-null, it is
    159     *  expected that this value will be either Boolean.TRUE or Boolean.FALSE.
    160     *  The special value BooleanConverter.NO_DEFAULT can also be passed here,
    161     *  in which case an exception will be thrown on conversion failure.
    162     * @since 1.8.0
    163     */
    164    public BooleanConverter(final String[] trueStrings, final String[] falseStrings,
    165                final Object defaultValue) {
    166        this.trueStrings = copyStrings(trueStrings);
    167        this.falseStrings = copyStrings(falseStrings);
    168        if (defaultValue != NO_DEFAULT) {
    169            setDefaultValue(defaultValue);
    170        }
    171    }
    172
    173    /**
    174     * Convert the specified input object into an output object of the
    175     * specified type.
    176     *
    177     * @param <T> Target type of the conversion.
    178     * @param type is the type to which this value should be converted. In the
    179     *  case of this BooleanConverter class, this value is ignored.
    180     *
    181     * @param value is the input value to be converted. The toString method
    182     *  shall be invoked on this object, and the result compared (ignoring
    183     *  case) against the known "true" and "false" string values.
    184     *
    185     * @return Boolean.TRUE if the value was a recognized "true" value,
    186     *  Boolean.FALSE if the value was a recognized "false" value, or
    187     *  the default value if the value was not recognized and the constructor
    188     *  was provided with a default value.
    189     *
    190     * @throws Throwable if an error occurs converting to the specified type
    191     * @since 1.8.0
    192     */
    193    @Override
    194    protected <T> T convertToType(final Class<T> type, final Object value) throws Throwable {
    195
    196        if (Boolean.class.equals(type) || Boolean.TYPE.equals(type)) {
    197            // All the values in the trueStrings and falseStrings arrays are
    198            // guaranteed to be lower-case. By converting the input value
    199            // to lowercase too, we can use the efficient String.equals method
    200            // instead of the less-efficient String.equalsIgnoreCase method.
    201            final String stringValue = value.toString().toLowerCase();
    202
    203            for (final String trueString : trueStrings) {
    204                if (trueString.equals(stringValue)) {
    205                    return type.cast(Boolean.TRUE);
    206                }
    207            }
    208
    209            for (final String falseString : falseStrings) {
    210                if (falseString.equals(stringValue)) {
    211                    return type.cast(Boolean.FALSE);
    212                }
    213            }
    214        }
    215
    216        throw conversionException(type, value);
    217    }
    218
    219    /**
    220     * Return the default type this <code>Converter</code> handles.
    221     *
    222     * @return The default type this <code>Converter</code> handles.
    223     * @since 1.8.0
    224     */
    225    @Override
    226    protected Class<Boolean> getDefaultType() {
    227        return Boolean.class;
    228    }
    229}