001/*
002 * Copyright 2002-2020 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.core.env;
018
019import org.springframework.util.ObjectUtils;
020
021/**
022 * A {@link PropertySource} implementation capable of interrogating its
023 * underlying source object to enumerate all possible property name/value
024 * pairs. Exposes the {@link #getPropertyNames()} method to allow callers
025 * to introspect available properties without having to access the underlying
026 * source object. This also facilitates a more efficient implementation of
027 * {@link #containsProperty(String)}, in that it can call {@link #getPropertyNames()}
028 * and iterate through the returned array rather than attempting a call to
029 * {@link #getProperty(String)} which may be more expensive. Implementations may
030 * consider caching the result of {@link #getPropertyNames()} to fully exploit this
031 * performance opportunity.
032 *
033 * <p>Most framework-provided {@code PropertySource} implementations are enumerable;
034 * a counter-example would be {@code JndiPropertySource} where, due to the
035 * nature of JNDI it is not possible to determine all possible property names at
036 * any given time; rather it is only possible to try to access a property
037 * (via {@link #getProperty(String)}) in order to evaluate whether it is present
038 * or not.
039 *
040 * @author Chris Beams
041 * @author Juergen Hoeller
042 * @since 3.1
043 * @param <T> the source type
044 */
045public abstract class EnumerablePropertySource<T> extends PropertySource<T> {
046
047        /**
048         * Create a new {@code EnumerablePropertySource} with the given name and source object.
049         * @param name the associated name
050         * @param source the source object
051         */
052        public EnumerablePropertySource(String name, T source) {
053                super(name, source);
054        }
055
056        /**
057         * Create a new {@code EnumerablePropertySource} with the given name and with a new
058         * {@code Object} instance as the underlying source.
059         * @param name the associated name
060         */
061        protected EnumerablePropertySource(String name) {
062                super(name);
063        }
064
065
066        /**
067         * Return whether this {@code PropertySource} contains a property with the given name.
068         * <p>This implementation checks for the presence of the given name within the
069         * {@link #getPropertyNames()} array.
070         * @param name the name of the property to find
071         */
072        @Override
073        public boolean containsProperty(String name) {
074                return ObjectUtils.containsElement(getPropertyNames(), name);
075        }
076
077        /**
078         * Return the names of all properties contained by the
079         * {@linkplain #getSource() source} object (never {@code null}).
080         */
081        public abstract String[] getPropertyNames();
082
083}