001 /*
002 * JBoss DNA (http://www.jboss.org/dna)
003 * See the COPYRIGHT.txt file distributed with this work for information
004 * regarding copyright ownership. Some portions may be licensed
005 * to Red Hat, Inc. under one or more contributor license agreements.
006 * See the AUTHORS.txt file in the distribution for a full listing of
007 * individual contributors.
008 *
009 * JBoss DNA is free software. Unless otherwise indicated, all code in JBoss DNA
010 * is licensed to you under the terms of the GNU Lesser General Public License as
011 * published by the Free Software Foundation; either version 2.1 of
012 * the License, or (at your option) any later version.
013 *
014 * JBoss DNA is distributed in the hope that it will be useful,
015 * but WITHOUT ANY WARRANTY; without even the implied warranty of
016 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
017 * Lesser General Public License for more details.
018 *
019 * You should have received a copy of the GNU Lesser General Public
020 * License along with this software; if not, write to the Free
021 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
022 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
023 */
024 package org.jboss.dna.graph.property;
025
026 import java.util.Iterator;
027 import net.jcip.annotations.Immutable;
028
029 /**
030 * Representation of a property consisting of a name and value(s). Note that this property is immutable, meaning that the property
031 * values may not be changed through this interface.
032 * <p>
033 * This class is designed to be used with the {@link ValueFactories} interface and the particular {@link ValueFactory} that
034 * corresponds to the type of value you'd like to use. The <code>ValueFactory</code> will then return the values (if no type
035 * conversion is required) or will convert the values using the appropriate conversion algorithm.
036 * </p>
037 * <p>
038 * The following example shows how to obtain the {@link String} representations of the {@link #getValues() property values}:
039 *
040 * <pre>
041 * ValueFactories valueFactories = ...
042 * Property property = ...
043 * Iterator<String> iter = valueFactories.getStringFactory().create(property.getValues());
044 * while ( iter.hasNext() ) {
045 * System.out.println(iter.next());
046 * }
047 * </pre>
048 *
049 * Meanwhile, the {@link ValueFactories#getLongFactory() long value factory} converts the values to <code>long</code>, the
050 * {@link ValueFactories#getDateFactory() date value factory} converts the values to {@link DateTime} instances, and so on.
051 * </p>
052 * <p>
053 * This technique is much better and far safer than casting the values. It is possible that some Property instances contain
054 * heterogeneous values, so casting may not always work. Also, this technique guarantees that the values are properly converted if
055 * the type is not what you expected.
056 * </p>
057 *
058 * @author Randall Hauch
059 */
060 @Immutable
061 public interface Property extends Iterable<Object>, Comparable<Property>, Readable {
062
063 /**
064 * Get the name of the property.
065 *
066 * @return the property name; never null
067 */
068 Name getName();
069
070 /**
071 * Get the number of actual values in this property. If the property allows {@link #isMultiple() multiple values}, then this
072 * method may return a value greater than 1. If the property only allows a {@link #isSingle() single value}, then this method
073 * will return either 0 or 1. This method may return 0 regardless of whether the property allows a {@link #isSingle() single
074 * value}, or {@link #isMultiple() multiple values}.
075 *
076 * @return the number of actual values in this property; always non-negative
077 */
078 int size();
079
080 /**
081 * Determine whether the property currently has multiple values.
082 *
083 * @return true if the property has multiple values, or false otherwise.
084 * @see #isSingle()
085 * @see #isEmpty()
086 */
087 boolean isMultiple();
088
089 /**
090 * Determine whether the property currently has a single value.
091 *
092 * @return true if the property has a single value, or false otherwise.
093 * @see #isMultiple()
094 * @see #isEmpty()
095 */
096 boolean isSingle();
097
098 /**
099 * Determine whether this property has no actual values. This method may return <code>true</code> regardless of whether the
100 * property allows a {@link #isSingle() single value}, or {@link #isMultiple() multiple values}.
101 * <p>
102 * This method is a convenience method that is equivalent to <code>size() == 0</code>.
103 * </p>
104 *
105 * @return true if this property has no values, or false otherwise
106 * @see #isMultiple()
107 * @see #isSingle()
108 */
109 boolean isEmpty();
110
111 /**
112 * Obtain the property's first value in its natural form. This is equivalent to calling
113 * <code>isEmpty() ? null : iterator().next()</code>
114 *
115 * @return the first value, or null if the property is {@link #isEmpty() empty}
116 * @see Iterable#iterator()
117 * @see #getValues()
118 * @see #getValuesAsArray()
119 * @see #isEmpty()
120 */
121 Object getFirstValue();
122
123 /**
124 * Obtain the property's values in their natural form. This is equivalent to calling {@link Iterable#iterator() iterator()}.
125 * <p>
126 * A valid iterator is returned if the property has {@link #isSingle() single valued} or {@link #isMultiple() multi-valued}.
127 * </p>
128 * <p>
129 * The resulting iterator is immutable, and all property values are immutable.
130 * </p>
131 *
132 * @return an iterator over the values; never null
133 * @see #getFirstValue()
134 * @see Iterable#iterator()
135 * @see #getValuesAsArray()
136 * @see ValueFactory#create(Iterator)
137 */
138 Iterator<?> getValues();
139
140 /**
141 * Obtain the property's values as an array of objects in their natural form.
142 * <p>
143 * A valid array is return if the property has {@link #isSingle() single valued} or {@link #isMultiple() multi-valued}, or a
144 * null value is returned if the property is {@link #isEmpty() empty}.
145 * </p>
146 * <p>
147 * The resulting array is a copy, guaranteeing immutability for the property.
148 * </p>
149 *
150 * @return the array of values
151 * @see #getFirstValue()
152 * @see Iterable#iterator()
153 * @see #getValues()
154 * @see ValueFactory#create(Object[])
155 */
156 Object[] getValuesAsArray();
157 }