com.expedia.seiso.web.hateoas.link.PaginationLinkBuilder.java Source code

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Here is the source code for com.expedia.seiso.web.hateoas.link.PaginationLinkBuilder.java

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/* 
 * Copyright 2013-2015 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 com.expedia.seiso.web.hateoas.link;

import lombok.NonNull;
import lombok.RequiredArgsConstructor;
import lombok.val;

import org.springframework.data.domain.Page;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.web.util.UriComponents;
import org.springframework.web.util.UriComponentsBuilder;

import com.expedia.seiso.web.Relations;
import com.expedia.seiso.web.hateoas.Link;

/**
 * Builder for pagination links (self, first, previous, next, last). This is for paging resources generally, not for any
 * particular kind of paging resource (e.g. repo search). So we don't include the "up" relation here, since that would
 * require knowledge of the parent resource.
 * 
 * @author Willie Wheeler
 */
@RequiredArgsConstructor
public class PaginationLinkBuilder {
    @NonNull
    private Page page;
    @NonNull
    private UriComponents uriComponents;
    @NonNull
    private MultiValueMap<String, String> params;

    public Link buildSelfLink() {
        // @formatter:off
        val href = uriComponentsBuilder().queryParams(params).build().toString();
        // @formatter:on
        return new Link(Relations.SELF, href);
    }

    public Link buildFirstLink() {
        val totalPages = page.getTotalPages();
        val firstPage = 0;

        if (totalPages <= 0) {
            return null;
        }

        // @formatter:off
        val href = uriComponentsBuilder().queryParams(paramsWithReplacementPageNumber(firstPage)).build()
                .toString();
        // @formatter:on
        return new Link(Relations.FIRST, href);
    }

    public Link buildPreviousLink() {
        val totalPages = page.getTotalPages();
        val firstPage = 0;
        val currentPage = page.getNumber();

        if (totalPages <= 0 || currentPage <= firstPage) {
            return null;
        }

        // @formatter:off
        val href = uriComponentsBuilder().queryParams(paramsWithReplacementPageNumber(currentPage - 1)).build()
                .toString();
        // @formatter:on

        return new Link(Relations.PREVIOUS, href);
    }

    public Link buildNextLink() {
        val totalPages = page.getTotalPages();
        val lastPage = totalPages - 1;
        val currentPage = page.getNumber();

        if (totalPages <= 0 || currentPage >= lastPage) {
            return null;
        }

        // @formatter:off
        val href = uriComponentsBuilder().queryParams(paramsWithReplacementPageNumber(currentPage + 1)).build()
                .toString();
        // @formatter:on

        return new Link(Relations.NEXT, href);
    }

    public Link buildLastLink() {
        val totalPages = page.getTotalPages();
        val lastPage = totalPages - 1;

        if (totalPages <= 0) {
            return null;
        }

        // @formatter:off
        val href = uriComponentsBuilder().queryParams(paramsWithReplacementPageNumber(lastPage)).build().toString();
        // @formatter:on

        return new Link(Relations.LAST, href);
    }

    private UriComponentsBuilder uriComponentsBuilder() {
        return UriComponentsBuilder.fromUri(uriComponents.toUri());
    }

    private MultiValueMap<String, String> paramsWithReplacementPageNumber(int pageNumber) {
        val newParams = new LinkedMultiValueMap<String, String>(params);
        newParams.set("page", String.valueOf(pageNumber));
        return newParams;
    }
}