org.springframework.data.rest.core.support.DefaultSelfLinkProvider.java Source code

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Here is the source code for org.springframework.data.rest.core.support.DefaultSelfLinkProvider.java

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/*
 * Copyright 2015-2019 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.core.support;

import java.util.List;

import org.springframework.data.mapping.context.PersistentEntities;
import org.springframework.hateoas.Link;
import org.springframework.hateoas.server.EntityLinks;
import org.springframework.plugin.core.PluginRegistry;
import org.springframework.util.Assert;

/**
 * Default implementation of SelfLinkProvider that uses an {@link EntityLinks} instance to create self links. Considers
 * the configured {@link EntityLookup}s to use the returned resource identifier to eventually create the link.
 *
 * @author Oliver Gierke
 * @since 2.5
 * @soundtrack Trio Rotation - Travis
 */
public class DefaultSelfLinkProvider implements SelfLinkProvider {

    private final PersistentEntities entities;
    private final EntityLinks entityLinks;
    private final PluginRegistry<EntityLookup<?>, Class<?>> lookups;

    /**
     * Creates a new {@link DefaultSelfLinkProvider} from the {@link PersistentEntities}, {@link EntityLinks} and
     * {@link EntityLookup}s.
     *
     * @param entities must not be {@literal null}.
     * @param entityLinks must not be {@literal null}.
     * @param lookups must not be {@literal null}.
     */
    public DefaultSelfLinkProvider(PersistentEntities entities, EntityLinks entityLinks,
            List<? extends EntityLookup<?>> lookups) {

        Assert.notNull(entities, "PersistentEntities must not be null!");
        Assert.notNull(entityLinks, "EntityLinks must not be null!");
        Assert.notNull(lookups, "EntityLookups must not be null!");

        this.entities = entities;
        this.entityLinks = entityLinks;
        this.lookups = PluginRegistry.of(lookups);
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.rest.core.support.SelfLinkProvider#createSelfLinkFor(java.lang.Object)
     */
    public Link createSelfLinkFor(Object instance) {

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

        return entityLinks.linkToItemResource(instance.getClass(), getResourceId(instance));
    }

    /**
     * Returns the identifier to be used to create the self link URI.
     *
     * @param instance must not be {@literal null}.
     * @return
     */
    @SuppressWarnings("unchecked")
    private Object getResourceId(Object instance) {

        Class<? extends Object> instanceType = instance.getClass();

        return lookups.getPluginFor(instanceType)//
                .map(it -> it.getClass().cast(it))//
                .map(it -> it.getResourceIdentifier(instance))//
                .orElseGet(() -> identifierOrNull(instance));
    }

    private Object identifierOrNull(Object instance) {

        return entities.getRequiredPersistentEntity(instance.getClass())//
                .getIdentifierAccessor(instance).getIdentifier();
    }
}