Oliver Drotbohm
3 years ago
4 changed files with 1 additions and 406 deletions
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/* |
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* Copyright 2019-2023 the original author or authors. |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* https://www.apache.org/licenses/LICENSE-2.0
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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package org.springframework.data.mapping; |
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import java.util.Collection; |
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import java.util.HashMap; |
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import java.util.List; |
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import java.util.Map; |
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import java.util.Set; |
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import java.util.function.Function; |
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import org.springframework.lang.Nullable; |
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import org.springframework.util.Assert; |
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/** |
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* A context object for lookups of values for {@link PersistentPropertyPaths} via a {@link PersistentPropertyAccessor}. |
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* It allows to register functions to post-process the objects returned for a particular property, so that the |
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* subsequent traversal would rather use the processed object. This is especially helpful if you need to traverse paths |
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* that contain {@link Collection}s and {@link Map} that usually need indices and keys to reasonably traverse nested |
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* properties. |
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* |
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* @author Oliver Drotbohm |
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* @since 2.2 |
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* @soundtrack 8-Bit Misfits - Crash Into Me (Dave Matthews Band cover) |
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*/ |
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public class TraversalContext { |
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private Map<PersistentProperty<?>, Function<Object, Object>> handlers = new HashMap<>(); |
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/** |
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* Registers a {@link Function} to post-process values for the given property. |
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* |
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* @param property must not be {@literal null}. |
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* @param handler must not be {@literal null}. |
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* @return |
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*/ |
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public TraversalContext registerHandler(PersistentProperty<?> property, Function<Object, Object> handler) { |
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Assert.notNull(property, "Property must not be null"); |
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Assert.notNull(handler, "Handler must not be null"); |
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handlers.put(property, handler); |
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return this; |
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} |
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/** |
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* Registers a {@link Function} to handle {@link Collection} values for the given property. |
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* |
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* @param property must not be {@literal null}. |
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* @param handler must not be {@literal null}. |
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* @return |
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*/ |
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@SuppressWarnings("unchecked") |
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public TraversalContext registerCollectionHandler(PersistentProperty<?> property, |
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Function<? super Collection<?>, Object> handler) { |
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return registerHandler(property, Collection.class, (Function<Object, Object>) handler); |
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} |
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/** |
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* Registers a {@link Function} to handle {@link List} values for the given property. |
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* |
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* @param property must not be {@literal null}. |
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* @param handler must not be {@literal null}. |
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* @return |
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*/ |
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@SuppressWarnings("unchecked") |
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public TraversalContext registerListHandler(PersistentProperty<?> property, |
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Function<? super List<?>, Object> handler) { |
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return registerHandler(property, List.class, (Function<Object, Object>) handler); |
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} |
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/** |
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* Registers a {@link Function} to handle {@link Set} values for the given property. |
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* |
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* @param property must not be {@literal null}. |
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* @param handler must not be {@literal null}. |
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* @return |
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*/ |
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@SuppressWarnings("unchecked") |
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public TraversalContext registerSetHandler(PersistentProperty<?> property, Function<? super Set<?>, Object> handler) { |
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return registerHandler(property, Set.class, (Function<Object, Object>) handler); |
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} |
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/** |
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* Registers a {@link Function} to handle {@link Map} values for the given property. |
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* |
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* @param property must not be {@literal null}. |
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* @param handler must not be {@literal null}. |
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* @return |
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*/ |
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@SuppressWarnings("unchecked") |
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public TraversalContext registerMapHandler(PersistentProperty<?> property, |
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Function<? super Map<?, ?>, Object> handler) { |
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return registerHandler(property, Map.class, (Function<Object, Object>) handler); |
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} |
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/** |
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* Registers the given {@link Function} to post-process values obtained for the given {@link PersistentProperty} for |
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* the given type. |
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* |
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* @param <T> the type of the value to handle. |
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* @param property must not be {@literal null}. |
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* @param type must not be {@literal null}. |
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* @param handler must not be {@literal null}. |
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* @return |
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*/ |
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public <T> TraversalContext registerHandler(PersistentProperty<?> property, Class<T> type, |
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Function<? super T, Object> handler) { |
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Assert.isTrue(type.isAssignableFrom(property.getType()), () -> String |
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.format("Cannot register a property handler for %s on a property of type %s", type, property.getType())); |
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Function<Object, T> caster = (Function<Object, T>) it -> type.cast(it); |
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return registerHandler(property, caster.andThen(handler)); |
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} |
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/** |
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* Post-processes the value obtained for the given {@link PersistentProperty} using the registered handler. |
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* |
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* @param property must not be {@literal null}. |
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* @param value can be {@literal null}. |
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* @return the post-processed value or the value itself if no handlers registered. |
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*/ |
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@Nullable |
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Object postProcess(PersistentProperty<?> property, @Nullable Object value) { |
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Function<Object, Object> handler = handlers.get(property); |
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return handler == null ? value : handler.apply(value); |
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} |
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} |
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