GeneratingIdAccessor.java

/*
 * Copyright 2014 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
 *
 *      http://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.keyvalue.core;

import java.io.Serializable;
import java.util.Optional;

import org.springframework.data.mapping.IdentifierAccessor;
import org.springframework.data.mapping.PersistentProperty;
import org.springframework.data.mapping.PersistentPropertyAccessor;
import org.springframework.util.Assert;

/**
 * {@link IdentifierAccessor} adding a {@link #getOrGenerateIdentifier()} to automatically generate an identifier and
 * set it on the underling bean instance.
 * 
 * @author Oliver Gierke
 * @see #getOrGenerateIdentifier()
 */
class GeneratingIdAccessor implements IdentifierAccessor {

	private final PersistentPropertyAccessor accessor;
	private final PersistentProperty<?> identifierProperty;
	private final IdentifierGenerator generator;

	/**
	 * Creates a new {@link GeneratingIdAccessor} using the given {@link PersistentPropertyAccessor}, identifier property
	 * and {@link IdentifierGenerator}.
	 * 
	 * @param accessor must not be {@literal null}.
	 * @param identifierProperty must not be {@literal null}.
	 * @param generator must not be {@literal null}.
	 */
	public GeneratingIdAccessor(PersistentPropertyAccessor accessor, PersistentProperty<?> identifierProperty,
			IdentifierGenerator generator) {

		Assert.notNull(accessor, "PersistentPropertyAccessor must not be null!");
		Assert.notNull(identifierProperty, "Identifier property must not be null!");
		Assert.notNull(generator, "IdentifierGenerator must not be null!");

		this.accessor = accessor;
		this.identifierProperty = identifierProperty;
		this.generator = generator;
	}

	/*
	 * (non-Javadoc)
	 * @see org.springframework.data.keyvalue.core.IdentifierAccessor#getIdentifier()
	 */
	@Override
	public Optional<Object> getIdentifier() {
		return accessor.getProperty(identifierProperty);
	}

	/**
	 * Returns the identifier value of the backing bean or generates a new one using the configured
	 * {@link IdentifierGenerator}.
	 * 
	 * @return
	 */
	public Object getOrGenerateIdentifier() {

		Optional<Object> existingIdentifier = getIdentifier();

		if (existingIdentifier.isPresent()) {
			return existingIdentifier.get();
		}

		Object generatedIdentifier = generator.generateIdentifierOfType(identifierProperty.getTypeInformation());
		accessor.setProperty(identifierProperty, Optional.ofNullable(generatedIdentifier));

		return generatedIdentifier;
	}
}