001/*
002 * Copyright 2002-2017 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.web.reactive.result.condition;
018
019import java.util.Collection;
020import java.util.Collections;
021
022import org.springframework.lang.Nullable;
023import org.springframework.web.server.ServerWebExchange;
024
025/**
026 * A holder for a {@link RequestCondition} useful when the type of the request
027 * condition is not known ahead of time, e.g. custom condition. Since this
028 * class is also an implementation of {@code RequestCondition}, effectively it
029 * decorates the held request condition and allows it to be combined and compared
030 * with other request conditions in a type and null safe way.
031 *
032 * <p>When two {@code RequestConditionHolder} instances are combined or compared
033 * with each other, it is expected the conditions they hold are of the same type.
034 * If they are not, a {@link ClassCastException} is raised.
035 *
036 * @author Rossen Stoyanchev
037 * @since 5.0
038 */
039public final class RequestConditionHolder extends AbstractRequestCondition<RequestConditionHolder> {
040
041        @Nullable
042        private final RequestCondition<Object> condition;
043
044
045        /**
046         * Create a new holder to wrap the given request condition.
047         * @param requestCondition the condition to hold (may be {@code null})
048         */
049        @SuppressWarnings("unchecked")
050        public RequestConditionHolder(@Nullable RequestCondition<?> requestCondition) {
051                this.condition = (RequestCondition<Object>) requestCondition;
052        }
053
054
055        /**
056         * Return the held request condition, or {@code null} if not holding one.
057         */
058        @Nullable
059        public RequestCondition<?> getCondition() {
060                return this.condition;
061        }
062
063        @Override
064        protected Collection<?> getContent() {
065                return (this.condition != null ? Collections.singleton(this.condition) : Collections.emptyList());
066        }
067
068        @Override
069        protected String getToStringInfix() {
070                return " ";
071        }
072
073        /**
074         * Combine the request conditions held by the two RequestConditionHolder
075         * instances after making sure the conditions are of the same type.
076         * Or if one holder is empty, the other holder is returned.
077         */
078        @Override
079        public RequestConditionHolder combine(RequestConditionHolder other) {
080                if (this.condition == null && other.condition == null) {
081                        return this;
082                }
083                else if (this.condition == null) {
084                        return other;
085                }
086                else if (other.condition == null) {
087                        return this;
088                }
089                else {
090                        assertEqualConditionTypes(this.condition, other.condition);
091                        RequestCondition<?> combined = (RequestCondition<?>) this.condition.combine(other.condition);
092                        return new RequestConditionHolder(combined);
093                }
094        }
095
096        /**
097         * Get the matching condition for the held request condition wrap it in a
098         * new RequestConditionHolder instance. Or otherwise if this is an empty
099         * holder, return the same holder instance.
100         */
101        @Override
102        public RequestConditionHolder getMatchingCondition(ServerWebExchange exchange) {
103                if (this.condition == null) {
104                        return this;
105                }
106                RequestCondition<?> match = (RequestCondition<?>) this.condition.getMatchingCondition(exchange);
107                return (match != null ? new RequestConditionHolder(match) : null);
108        }
109
110        /**
111         * Compare the request conditions held by the two RequestConditionHolder
112         * instances after making sure the conditions are of the same type.
113         * Or if one holder is empty, the other holder is preferred.
114         */
115        @Override
116        public int compareTo(RequestConditionHolder other, ServerWebExchange exchange) {
117                if (this.condition == null && other.condition == null) {
118                        return 0;
119                }
120                else if (this.condition == null) {
121                        return 1;
122                }
123                else if (other.condition == null) {
124                        return -1;
125                }
126                else {
127                        assertEqualConditionTypes(this.condition, other.condition);
128                        return this.condition.compareTo(other.condition, exchange);
129                }
130        }
131
132        /**
133         * Ensure the held request conditions are of the same type.
134         */
135        private void assertEqualConditionTypes(RequestCondition<?> cond1, RequestCondition<?> cond2) {
136                Class<?> clazz = cond1.getClass();
137                Class<?> otherClazz = cond2.getClass();
138                if (!clazz.equals(otherClazz)) {
139                        throw new ClassCastException("Incompatible request conditions: " + clazz + " vs " + otherClazz);
140                }
141        }
142
143}