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Spring Data module to provide sophisticated support for JPA repositories
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/*
 * Copyright 2008-2011 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.jpa.domain;

import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;

/**
 * Helper class to easily combine {@link Specification} instances.
 * 
 * @author Oliver Gierke
 */
public class Specifications implements Specification {

	private final Specification spec;

	/**
	 * Creates a new {@link Specifications} wrapper for the given {@link Specification}.
	 * 
	 * @param spec
	 */
	private Specifications(Specification spec) {

		this.spec = spec;
	}

	/**
	 * Simple static factory method to add some syntactic sugar around a {@link Specification}.
	 * 
	 * @param 
	 * @param spec
	 * @return
	 */
	public static  Specifications where(Specification spec) {

		return new Specifications(spec);
	}

	/**
	 * ANDs the given {@link Specification} to the current one.
	 * 
	 * @param other
	 * @return
	 */
	public Specifications and(final Specification other) {

		return new Specifications(new Specification() {

			public Predicate toPredicate(Root root, CriteriaQuery query, CriteriaBuilder builder) {

				return builder.and(spec.toPredicate(root, query, builder), other.toPredicate(root, query, builder));
			}
		});
	}

	/**
	 * ORs the given specification to the current one.
	 * 
	 * @param other
	 * @return
	 */
	public Specifications or(final Specification other) {

		return new Specifications(new Specification() {

			public Predicate toPredicate(Root root, CriteriaQuery query, CriteriaBuilder builder) {

				return builder.or(spec.toPredicate(root, query, builder), other.toPredicate(root, query, builder));
			}
		});
	}

	/**
	 * Negates the given {@link Specification}.
	 * 
	 * @param 
	 * @param spec
	 * @return
	 */
	public static  Specifications not(final Specification spec) {

		return new Specifications(spec) {

			@Override
			public Predicate toPredicate(Root root, CriteriaQuery query, CriteriaBuilder builder) {

				return builder.not(spec.toPredicate(root, query, builder));
			}
		};
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.springframework.data.jpa.domain.Specification#toPredicate(javax.
	 * persistence.criteria.Root, javax.persistence.criteria.CriteriaQuery,
	 * javax.persistence.criteria.CriteriaBuilder)
	 */
	public Predicate toPredicate(Root root, CriteriaQuery query, CriteriaBuilder builder) {

		return spec.toPredicate(root, query, builder);
	}
}