org.matonto.rest.util.LinksUtils.java Source code

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Here is the source code for org.matonto.rest.util.LinksUtils.java

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package org.matonto.rest.util;

/*-
 * #%L
 * org.matonto.rest.util
 * $Id:$
 * $HeadURL:$
 * %%
 * Copyright (C) 2016 iNovex Information Systems, Inc.
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * 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.
 * 
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 * #L%
 */

import org.apache.http.NameValuePair;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.message.BasicNameValuePair;
import org.matonto.rest.util.jaxb.Links;

import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.UriInfo;

public class LinksUtils {

    private static String buildQueryString(MultivaluedMap<String, String> queryParams, int start) {
        List<NameValuePair> params = new ArrayList<>();

        queryParams.forEach((key, values) -> {
            if (key.equals("offset")) {
                params.add(new BasicNameValuePair(key, String.valueOf(start)));
            } else {
                params.add(new BasicNameValuePair(key, values.get(0)));
            }
        });

        return URLEncodedUtils.format(params, '&', Charset.forName("UTF-8"));
    }

    /**
     * Creates the Links that will be used to get the next and previous page of results based off of the provided
     * details.
     *
     * @param uriInfo the request URI information.
     * @param size the number of results returned.
     * @param limit the maximum number of results returned.
     * @param offset the offset of the results.
     * @return Links for the provided details.
     */
    public static Links buildLinks(UriInfo uriInfo, int size, int totalSize, int limit, int offset) {
        String path = uriInfo.getPath(false);

        Links links = new Links();
        links.setBase(uriInfo.getBaseUri().toString());
        links.setSelf(uriInfo.getAbsolutePath().toString());
        links.setContext(path);

        if (size == limit && totalSize - (offset + limit) > 0) {
            String next = path + "?" + buildQueryString(uriInfo.getQueryParameters(), offset + limit);
            links.setNext(next);
        }

        if (offset != 0) {
            String prev = path + "?" + buildQueryString(uriInfo.getQueryParameters(), offset - limit);
            links.setPrev(prev);
        }

        return links;
    }

    /**
     * Checks whether the passed limit and offset values are valid pagination parameters. The
     * offset must not be negative and the limits must not be zero or negative.
     *
     * @param limit the maximum number of results to return
     * @param offset the offset of the results
     */
    public static void validateParams(int limit, int offset) {
        if (offset < 0) {
            throw ErrorUtils.sendError("Offset cannot be negative.", Response.Status.BAD_REQUEST);
        }
        if (limit <= 0) {
            throw ErrorUtils.sendError("Limit must be positive", Response.Status.BAD_REQUEST);
        }
    }
}