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.beanutils2.converters;
018
019/**
020 * {@link org.apache.commons.beanutils2.Converter} implementation that handles conversion to and from <strong>Boolean</strong> objects.
021 * {@link org.apache.commons.beanutils2.Converter} implementation that handles conversion to and from {@link Boolean} objects.
022 * <p>
023 * Can be configured to either return a <em>default value</em> or throw a {@code ConversionException} if a conversion error occurs.
024 * </p>
025 * <p>
026 * By default any object whose string representation is one of the values {"yes", "y", "true", "on", "1"} is converted to Boolean.TRUE, and string
027 * representations {"no", "n", "false", "off", "0"} are converted to Boolean.FALSE. The recognized true/false strings can be changed by:
028 * </p>
029 *
030 * <pre>
031 * String[] trueStrings = { "oui", "o", "1" };
032 * String[] falseStrings = { "non", "n", "0" };
033 * Converter bc = new BooleanConverter(trueStrings, falseStrings);
034 * ConvertUtils.register(bc, Boolean.class);
035 * ConvertUtils.register(bc, Boolean.TYPE);
036 * </pre>
037 *
038 * <p>
039 * Case is ignored when converting values to true or false.
040 * </p>
041 *
042 * @since 1.3
043 */
044public final class BooleanConverter extends AbstractConverter<Boolean> {
045
046    /**
047     * Copies the provided array, and ensures that all the strings in the newly created array contain only lower-case letters.
048     * <p>
049     * Using this method to copy string arrays means that changes to the src array do not modify the dst array.
050     * </p>
051     */
052    private static String[] copyStrings(final String[] src) {
053        final String[] dst = new String[src.length];
054        for (int i = 0; i < src.length; ++i) {
055            dst[i] = toLowerCase(src[i]);
056        }
057        return dst;
058    }
059
060    /**
061     * The set of strings that are known to map to Boolean.TRUE.
062     */
063    private String[] trueStrings = { "true", "yes", "y", "on", "1" };
064
065    /**
066     * The set of strings that are known to map to Boolean.FALSE.
067     */
068    private String[] falseStrings = { "false", "no", "n", "off", "0" };
069
070    /**
071     * Constructs a {@link org.apache.commons.beanutils2.Converter} that will throw a {@link org.apache.commons.beanutils2.ConversionException} if a conversion
072     * error occurs, that is, if the string value being converted is not one of the known true strings, nor one of the known false strings.
073     */
074    public BooleanConverter() {
075    }
076
077    /**
078     * Constructs a {@link org.apache.commons.beanutils2.Converter} that will return the specified default value if a conversion error occurs, that is, the
079     * string value being converted is not one of the known true strings, nor one of the known false strings.
080     *
081     * @param defaultValue The default value to be returned if the value being converted is not recognized. This value may be null, in which case null will be
082     *                     returned on conversion failure. When non-null, it is expected that this value will be either Boolean.TRUE or Boolean.FALSE. The
083     *                     special value BooleanConverter.NO_DEFAULT can also be passed here, in which case this constructor acts like the no-argument one.
084     */
085    public BooleanConverter(final Boolean defaultValue) {
086        super(defaultValue);
087    }
088
089    /**
090     * Constructs a {@link org.apache.commons.beanutils2.Converter} that will throw a {@link org.apache.commons.beanutils2.ConversionException} if a conversion
091     * error occurs, that is, the string value being converted is not one of the known true strings, nor one of the known false strings.
092     * <p>
093     * The provided string arrays are copied, so that changes to the elements of the array after this call is made do not affect this object.
094     *
095     * @param trueStrings  is the set of strings which should convert to the value Boolean.TRUE. The value null must not be present. Case is ignored.
096     * @param falseStrings is the set of strings which should convert to the value Boolean.TRUE. The value null must not be present. Case is ignored.
097     * @since 1.8.0
098     */
099    public BooleanConverter(final String[] trueStrings, final String[] falseStrings) {
100        this.trueStrings = copyStrings(trueStrings);
101        this.falseStrings = copyStrings(falseStrings);
102    }
103
104    /**
105     * Constructs a {@link org.apache.commons.beanutils2.Converter} that will return the specified default value if a conversion error occurs.
106     * <p>
107     * The provided string arrays are copied, so that changes to the elements of the array after this call is made do not affect this object.
108     *
109     * @param trueStrings  is the set of strings which should convert to the value Boolean.TRUE. The value null must not be present. Case is ignored.
110     * @param falseStrings is the set of strings which should convert to the value Boolean.TRUE. The value null must not be present. Case is ignored.
111     * @param defaultValue The default value to be returned if the value being converted is not recognized. This value may be null, in which case null will be
112     *                     returned on conversion failure. When non-null, it is expected that this value will be either Boolean.TRUE or Boolean.FALSE. The
113     *                     special value BooleanConverter.NO_DEFAULT can also be passed here, in which case an exception will be thrown on conversion failure.
114     * @since 1.8.0
115     */
116    public BooleanConverter(final String[] trueStrings, final String[] falseStrings, final Boolean defaultValue) {
117        super(defaultValue);
118        this.trueStrings = copyStrings(trueStrings);
119        this.falseStrings = copyStrings(falseStrings);
120    }
121
122    /**
123     * Converts the specified input object into an output object of the specified type.
124     *
125     * @param <T>   Target type of the conversion.
126     * @param type  is the type to which this value should be converted. In the case of this BooleanConverter class, this value is ignored.
127     * @param value is the input value to be converted. The toString method shall be invoked on this object, and the result compared (ignoring case) against the
128     *              known "true" and "false" string values.
129     *
130     * @return Boolean.TRUE if the value was a recognized "true" value, Boolean.FALSE if the value was a recognized "false" value, or the default value if the
131     *         value was not recognized and the constructor was provided with a default value.
132     *
133     * @throws Throwable if an error occurs converting to the specified type
134     * @since 1.8.0
135     */
136    @Override
137    protected <T> T convertToType(final Class<T> type, final Object value) throws Throwable {
138        if (Boolean.class.equals(type) || Boolean.TYPE.equals(type)) {
139            // All the values in the trueStrings and falseStrings arrays are
140            // guaranteed to be lower-case. By converting the input value
141            // to lowercase too, we can use the efficient String.equals method
142            // instead of the less-efficient String.equalsIgnoreCase method.
143            final String stringValue = toLowerCase(value);
144
145            for (final String trueString : trueStrings) {
146                if (trueString.equals(stringValue)) {
147                    return type.cast(Boolean.TRUE);
148                }
149            }
150
151            for (final String falseString : falseStrings) {
152                if (falseString.equals(stringValue)) {
153                    return type.cast(Boolean.FALSE);
154                }
155            }
156        }
157
158        throw conversionException(type, value);
159    }
160
161    /**
162     * Gets the default type this {@code Converter} handles.
163     *
164     * @return The default type this {@code Converter} handles.
165     * @since 1.8.0
166     */
167    @Override
168    protected Class<Boolean> getDefaultType() {
169        return Boolean.class;
170    }
171}