org.springframework.data.rest.webmvc.EmbeddedResourcesAssembler.java Source code

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Here is the source code for org.springframework.data.rest.webmvc.EmbeddedResourcesAssembler.java

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/*
 * Copyright 2016-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.data.rest.webmvc;

import lombok.NonNull;
import lombok.RequiredArgsConstructor;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import org.springframework.data.mapping.PersistentEntity;
import org.springframework.data.mapping.PersistentProperty;
import org.springframework.data.mapping.PersistentPropertyAccessor;
import org.springframework.data.mapping.SimpleAssociationHandler;
import org.springframework.data.mapping.context.PersistentEntities;
import org.springframework.data.rest.core.mapping.ResourceMetadata;
import org.springframework.data.rest.webmvc.mapping.Associations;
import org.springframework.data.rest.webmvc.support.ExcerptProjector;
import org.springframework.hateoas.LinkRelation;
import org.springframework.hateoas.server.core.EmbeddedWrapper;
import org.springframework.hateoas.server.core.EmbeddedWrappers;
import org.springframework.util.Assert;

/**
 * @author Oliver Gierke
 */
@RequiredArgsConstructor
public class EmbeddedResourcesAssembler {

    private final @NonNull PersistentEntities entities;
    private final @NonNull Associations associations;
    private final @NonNull ExcerptProjector projector;
    private final @NonNull EmbeddedWrappers wrappers = new EmbeddedWrappers(false);

    /**
     * Returns the embedded resources to render. This will add an {@link RelatedResource} for linkable associations if
     * they have an excerpt projection registered.
     *
     * @param instance must not be {@literal null}.
     * @return
     */
    public Iterable<EmbeddedWrapper> getEmbeddedResources(Object instance) {

        Assert.notNull(instance, "Entity instance must not be null!");

        PersistentEntity<?, ?> entity = entities.getRequiredPersistentEntity(instance.getClass());

        final List<EmbeddedWrapper> associationProjections = new ArrayList<EmbeddedWrapper>();
        final PersistentPropertyAccessor<?> accessor = entity.getPropertyAccessor(instance);
        final ResourceMetadata metadata = associations.getMetadataFor(entity.getType());

        entity.doWithAssociations((SimpleAssociationHandler) association -> {

            PersistentProperty<?> property = association.getInverse();

            if (!associations.isLinkableAssociation(property)) {
                return;
            }

            if (!projector.hasExcerptProjection(property.getActualType())) {
                return;
            }

            Object value = accessor.getProperty(association.getInverse());

            if (value == null) {
                return;
            }

            LinkRelation rel = metadata.getMappingFor(property).getRel();

            if (value instanceof Collection) {

                Collection<?> collection = (Collection<?>) value;

                if (collection.isEmpty()) {
                    return;
                }

                List<Object> nestedCollection = new ArrayList<Object>();

                for (Object element : collection) {
                    if (element != null) {
                        nestedCollection.add(projector.projectExcerpt(element));
                    }
                }

                associationProjections.add(wrappers.wrap(nestedCollection, rel));

            } else {
                associationProjections.add(wrappers.wrap(projector.projectExcerpt(value), rel));
            }
        });

        return associationProjections;
    }
}