OrderBySource.java

/*
 * Copyright 2008-2017 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.repository.query.parser;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.springframework.data.domain.Sort;
import org.springframework.data.domain.Sort.Direction;
import org.springframework.data.domain.Sort.Order;
import org.springframework.data.mapping.PropertyPath;
import org.springframework.util.StringUtils;

/**
 * Simple helper class to create a {@link Sort} instance from a method name end. It expects the last part of the method
 * name to be given and supports lining up multiple properties ending with the sorting direction. So the following
 * method ends are valid: {@code LastnameUsernameDesc}, {@code LastnameAscUsernameDesc}.
 * 
 * @author Oliver Gierke
 * @author Christoph Strobl
 * @author Mark Paluch
 */
class OrderBySource {

	public static OrderBySource EMPTY = new OrderBySource("");

	private static final String BLOCK_SPLIT = "(?<=Asc|Desc)(?=\\p{Lu})";
	private static final Pattern DIRECTION_SPLIT = Pattern.compile("(.+?)(Asc|Desc)?$");
	private static final String INVALID_ORDER_SYNTAX = "Invalid order syntax for part %s!";
	private static final Set<String> DIRECTION_KEYWORDS = new HashSet<>(Arrays.asList("Asc", "Desc"));

	private final List<Order> orders;

	/**
	 * Creates a new {@link OrderBySource} for the given String clause not doing any checks whether the referenced
	 * property actually exists.
	 * 
	 * @param clause must not be {@literal null}.
	 */
	public OrderBySource(String clause) {
		this(clause, Optional.empty());
	}

	/**
	 * Creates a new {@link OrderBySource} for the given clause, checking the property referenced exists on the given
	 * type.
	 * 
	 * @param clause must not be {@literal null}.
	 * @param domainClass must not be {@literal null}.
	 */
	public OrderBySource(String clause, Optional<Class<?>> domainClass) {

		this.orders = new ArrayList<>();

		if (!StringUtils.hasText(clause)) {
			return;
		}

		for (String part : clause.split(BLOCK_SPLIT)) {

			Matcher matcher = DIRECTION_SPLIT.matcher(part);

			if (!matcher.find()) {
				throw new IllegalArgumentException(String.format(INVALID_ORDER_SYNTAX, part));
			}

			String propertyString = matcher.group(1);
			String directionString = matcher.group(2);

			// No property, but only a direction keyword
			if (DIRECTION_KEYWORDS.contains(propertyString) && directionString == null) {
				throw new IllegalArgumentException(String.format(INVALID_ORDER_SYNTAX, part));
			}

			this.orders.add(createOrder(propertyString, Direction.fromOptionalString(directionString), domainClass));
		}
	}

	/**
	 * Creates an {@link Order} instance from the given property source, direction and domain class. If the domain class
	 * is given, we will use it for nested property traversal checks.
	 * 
	 * @param propertySource
	 * @param direction
	 * @param domainClass can be {@literal null}.
	 * @return
	 * @see PropertyPath#from(String, Class)
	 */
	private Order createOrder(String propertySource, Optional<Direction> direction, Optional<Class<?>> domainClass) {

		return domainClass.map(type -> {

			PropertyPath propertyPath = PropertyPath.from(propertySource, type);
			return direction.map(it -> new Order(it, propertyPath.toDotPath()))
					.orElseGet(() -> Order.by(propertyPath.toDotPath()));

		}).orElseGet(() -> direction//
				.map(it -> new Order(it, StringUtils.uncapitalize(propertySource)))
				.orElseGet(() -> Order.by(StringUtils.uncapitalize(propertySource))));
	}

	/**
	 * Returns the clause as {@link Sort}.
	 * 
	 * @return the {@link Sort}.
	 */
	public Sort toSort() {
		return Sort.by(this.orders);
	}

	/*
	 * (non-Javadoc)
	 * @see java.lang.Object#toString()
	 */
	@Override
	public String toString() {
		return "Order By " + StringUtils.collectionToDelimitedString(orders, ", ");
	}
}