001/**
002 *
003 * Copyright 2003-2007 Jive Software.
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * 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 */
017
018package org.jivesoftware.smack.filter;
019
020import java.util.function.Predicate;
021
022import org.jivesoftware.smack.packet.Stanza;
023
024/**
025 * Defines a way to filter stanzas for particular attributes. Stanza filters are used when
026 * constructing stanza listeners or collectors -- the filter defines what stanzas match the criteria
027 * of the collector or listener for further stanza processing.
028 * <p>
029 * Several simple filters are pre-defined. These filters can be logically combined for more complex
030 * stanza filtering by using the {@link org.jivesoftware.smack.filter.AndFilter AndFilter} and
031 * {@link org.jivesoftware.smack.filter.OrFilter OrFilter} filters. It's also possible to define
032 * your own filters by implementing this interface. The code example below creates a trivial filter
033 * for stanzas with a specific ID (real code should use {@link StanzaIdFilter} instead).
034 *
035 * <pre>
036 * // Use an anonymous inner class to define a stanza filter that returns
037 * // all stanzas that have a stanza ID of &quot;RS145&quot;.
038 * StanzaFilter myFilter = new StanzaFilter() {
039 *     public boolean accept(Stanza stanza) {
040 *         return &quot;RS145&quot;.equals(stanza.getStanzaId());
041 *     }
042 * };
043 * // Create a new stanza collector using the filter we created.
044 * StanzaCollector myCollector = connection.createStanzaCollector(myFilter);
045 * </pre>
046 * <p>
047 * As a rule of thumb: If you have a predicate method, that is, a method which takes a single Stanza as argument, is pure
048 * (side effect free) and returns only a boolean, then it is a good indicator that the logic should be put into a
049 * {@link StanzaFilter} (and be referenced in {@link org.jivesoftware.smack.StanzaListener}).
050 * </p>
051 *
052 * @see org.jivesoftware.smack.StanzaCollector
053 * @see org.jivesoftware.smack.StanzaListener
054 * @author Matt Tucker
055 */
056public interface StanzaFilter extends Predicate<Stanza> {
057
058    /**
059     * Tests whether or not the specified stanza should pass the filter.
060     *
061     * @param stanza the stanza to test.
062     * @return true if and only if <code>stanza</code> passes the filter.
063     */
064    boolean accept(Stanza stanza);
065
066    @Override
067    default boolean test(Stanza stanza) {
068        return accept(stanza);
069    }
070
071    default <S extends Stanza> Predicate<S> asPredicate(Class<?> stanzaClass) {
072        return s -> {
073            if (!stanzaClass.isAssignableFrom(s.getClass())) {
074                return false;
075            }
076            return accept(s);
077        };
078    }
079}