org.springframework.xd.dirt.util.PagingUtility.java Source code

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Here is the source code for org.springframework.xd.dirt.util.PagingUtility.java

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/*
 * 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.xd.dirt.util;

import java.util.Collections;
import java.util.List;

import org.apache.commons.collections.CollectionUtils;

import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageImpl;
import org.springframework.data.domain.Pageable;
import org.springframework.util.Assert;

/**
 * Utility class for paging support in repository accessor methods.
 *
 * @author Mark Fisher
 * @author Ilayaperumal Gopinathan
 * @author Gunnar Hillert
 */
public class PagingUtility<T extends Comparable<? super T>> {

    /**
     * Get the paged data of the given list.
     *
     * @param pageable the paging information, must not be null
     * @param list the list of content to paginate, must not be null
     * @return the paginated implementation of the given list of <T>
     * @throws PageNotFoundException in case an invalid page is requested
     */
    public Page<T> getPagedData(Pageable pageable, List<T> list) throws PageNotFoundException {

        Assert.notNull(pageable, "Pagination info can't be null.");
        Assert.notNull(list, "The provided list must not be null.");

        final int offset = pageable.getOffset();
        final int to = Math.min(list.size(), offset + pageable.getPageSize());

        if (offset > to) {
            throw new PageNotFoundException(String.format("Page %s does not exist.", pageable.getPageNumber()));
        }

        if (CollectionUtils.isEmpty(list)) {
            return new PageImpl<T>(list);
        }

        Collections.sort(list);

        final List<T> data = list.subList(offset, to);
        return new PageImpl<T>(data, pageable, list.size());
    }

}