org.n52.web.common.PageLinkUtil Maven / Gradle / Ivy

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/*
 * Copyright (C) 2013-2019 52°North Initiative for Geospatial Open Source
 * Software GmbH
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 *
 * If the program is linked with libraries which are licensed under one of
 * the following licenses, the combination of the program with the linked
 * library is not considered a "derivative work" of the program:
 *
 *     - Apache License, version 2.0
 *     - Apache Software License, version 1.0
 *     - GNU Lesser General Public License, version 3
 *     - Mozilla Public License, versions 1.0, 1.1 and 2.0
 *     - Common Development and Distribution License (CDDL), version 1.0
 *
 * Therefore the distribution of the program linked with libraries licensed
 * under the aforementioned licenses, is permitted by the copyright holders
 * if the distribution is compliant with both the GNU General Public License
 * version 2 and the aforementioned licenses.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
 * for more details.
 */
package org.n52.web.common;

import java.util.Optional;

import javax.servlet.http.HttpServletResponse;

public final class PageLinkUtil {

    private PageLinkUtil() {
        // no instance
    }

    public static void addPagingHeaders(String href, HttpServletResponse response, Paginated paginated) {
        addLinkHeader("self", href, paginated.getCurrent(), response);
        addLinkHeader("previous", href, paginated.getPrevious(), response);
        addLinkHeader("next", href, paginated.getNext(), response);
        addLinkHeader("first", href, paginated.getFirst(), response);
        addLinkHeader("last", href, paginated.getLast(), response);
    }

    private static void addLinkHeader(String rel,
                                      String href,
                                      Optional pagination,
                                      HttpServletResponse response) {
        if (pagination.isPresent()) {
            String header = "Link";
            Pagination pageLink = pagination.get();
            StringBuilder sb = new StringBuilder();
            String value = sb.append("<")
                             .append(href)
                             .append("?")
                             .append(pageLink.toString())
                             .append("> rel=\"")
                             .append(rel)
                             .append("\"")
                             .toString();
            response.addHeader(header, value);
        }
    }
}