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.http.codec.json;
018
019import java.lang.annotation.Annotation;
020import java.lang.reflect.Type;
021import java.util.Arrays;
022import java.util.Collections;
023import java.util.HashMap;
024import java.util.List;
025import java.util.Map;
026
027import com.fasterxml.jackson.annotation.JsonView;
028import com.fasterxml.jackson.databind.JavaType;
029import com.fasterxml.jackson.databind.ObjectMapper;
030import org.apache.commons.logging.Log;
031
032import org.springframework.core.GenericTypeResolver;
033import org.springframework.core.MethodParameter;
034import org.springframework.core.ResolvableType;
035import org.springframework.core.codec.Hints;
036import org.springframework.http.HttpLogging;
037import org.springframework.http.server.reactive.ServerHttpRequest;
038import org.springframework.http.server.reactive.ServerHttpResponse;
039import org.springframework.lang.Nullable;
040import org.springframework.util.Assert;
041import org.springframework.util.MimeType;
042import org.springframework.util.ObjectUtils;
043
044/**
045 * Base class providing support methods for Jackson 2.9 encoding and decoding.
046 *
047 * @author Sebastien Deleuze
048 * @author Rossen Stoyanchev
049 * @since 5.0
050 */
051public abstract class Jackson2CodecSupport {
052
053        /**
054         * The key for the hint to specify a "JSON View" for encoding or decoding
055         * with the value expected to be a {@link Class}.
056         * @see <a href="https://www.baeldung.com/jackson-json-view-annotation">Jackson JSON Views</a>
057         */
058        public static final String JSON_VIEW_HINT = Jackson2CodecSupport.class.getName() + ".jsonView";
059
060        /**
061         * The key for the hint to access the actual ResolvableType passed into
062         * {@link org.springframework.http.codec.HttpMessageReader#read(ResolvableType, ResolvableType, ServerHttpRequest, ServerHttpResponse, Map)}
063         * (server-side only). Currently set when the method argument has generics because
064         * in case of reactive types, use of {@code ResolvableType.getGeneric()} means no
065         * MethodParameter source and no knowledge of the containing class.
066         */
067        static final String ACTUAL_TYPE_HINT = Jackson2CodecSupport.class.getName() + ".actualType";
068
069        private static final String JSON_VIEW_HINT_ERROR =
070                        "@JsonView only supported for write hints with exactly 1 class argument: ";
071
072        private static final List<MimeType> DEFAULT_MIME_TYPES = Collections.unmodifiableList(
073                        Arrays.asList(
074                                        new MimeType("application", "json"),
075                                        new MimeType("application", "*+json")));
076
077
078        protected final Log logger = HttpLogging.forLogName(getClass());
079
080        private final ObjectMapper objectMapper;
081
082        private final List<MimeType> mimeTypes;
083
084
085        /**
086         * Constructor with a Jackson {@link ObjectMapper} to use.
087         */
088        protected Jackson2CodecSupport(ObjectMapper objectMapper, MimeType... mimeTypes) {
089                Assert.notNull(objectMapper, "ObjectMapper must not be null");
090                this.objectMapper = objectMapper;
091                this.mimeTypes = !ObjectUtils.isEmpty(mimeTypes) ?
092                                Collections.unmodifiableList(Arrays.asList(mimeTypes)) : DEFAULT_MIME_TYPES;
093        }
094
095
096        public ObjectMapper getObjectMapper() {
097                return this.objectMapper;
098        }
099
100        /**
101         * Subclasses should expose this as "decodable" or "encodable" mime types.
102         */
103        protected List<MimeType> getMimeTypes() {
104                return this.mimeTypes;
105        }
106
107
108        protected boolean supportsMimeType(@Nullable MimeType mimeType) {
109                return (mimeType == null || this.mimeTypes.stream().anyMatch(m -> m.isCompatibleWith(mimeType)));
110        }
111
112        protected JavaType getJavaType(Type type, @Nullable Class<?> contextClass) {
113                return this.objectMapper.constructType(GenericTypeResolver.resolveType(type, contextClass));
114        }
115
116        protected Map<String, Object> getHints(ResolvableType resolvableType) {
117                MethodParameter param = getParameter(resolvableType);
118                if (param != null) {
119                        Map<String, Object> hints = null;
120                        if (resolvableType.hasGenerics()) {
121                                hints = new HashMap<>(2);
122                                hints.put(ACTUAL_TYPE_HINT, resolvableType);
123                        }
124                        JsonView annotation = getAnnotation(param, JsonView.class);
125                        if (annotation != null) {
126                                Class<?>[] classes = annotation.value();
127                                Assert.isTrue(classes.length == 1, JSON_VIEW_HINT_ERROR + param);
128                                hints = (hints != null ? hints : new HashMap<>(1));
129                                hints.put(JSON_VIEW_HINT, classes[0]);
130                        }
131                        if (hints != null) {
132                                return hints;
133                        }
134                }
135                return Hints.none();
136        }
137
138        @Nullable
139        protected MethodParameter getParameter(ResolvableType type) {
140                return (type.getSource() instanceof MethodParameter ? (MethodParameter) type.getSource() : null);
141        }
142
143        @Nullable
144        protected abstract <A extends Annotation> A getAnnotation(MethodParameter parameter, Class<A> annotType);
145
146}