com.sonoport.freesound.response.mapping.PagingResponseMapper.java Source code

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Here is the source code for com.sonoport.freesound.response.mapping.PagingResponseMapper.java

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/*
 * Copyright 2014 Sonoport (Asia) Pte Ltd
 *
 * 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.sonoport.freesound.response.mapping;

import java.util.LinkedList;
import java.util.List;

import org.json.JSONArray;
import org.json.JSONObject;

/**
 * {@link Mapper} implementation used to parse JSON representation of a list of items that may spread over multiple
 * pages.
 *
 * @param <I> The data type of the individual items in the list
 */
public class PagingResponseMapper<I extends Object> extends Mapper<JSONObject, List<I>> {

    /** {@link Mapper} used to process the individual items in the list. */
    private final Mapper<JSONObject, I> itemMapper;

    /**
     * @param itemMapper {@link Mapper} used to process the individual items
     */
    public PagingResponseMapper(final Mapper<JSONObject, I> itemMapper) {
        this.itemMapper = itemMapper;
    }

    @Override
    public List<I> map(final JSONObject source) {
        final List<I> items = new LinkedList<>();
        final JSONArray resultsArray = extractFieldValue(source, "results", JSONArray.class);

        if (resultsArray != null) {
            for (int i = 0; i < resultsArray.length(); i++) {
                if (!resultsArray.isNull(i)) {
                    final JSONObject jsonObject = resultsArray.getJSONObject(i);
                    if ((jsonObject != null)) {
                        final I item = itemMapper.map(jsonObject);
                        items.add(item);
                    }
                }
            }
        }

        return items;
    }

    /**
     * Retrieve the total number of results for the query from the JSON message.
     *
     * @param source JSON response from freesound
     * @return Total number of results
     */
    public Integer extractCount(final JSONObject source) {
        return extractFieldValue(source, "count", Integer.class);
    }

    /**
     * Retrieve the URI of the next page of results (if any) for the query from the JSON message.
     *
     * @param source JSON response from freesound
     * @return Next page URI
     */
    public String extractNextPageURI(final JSONObject source) {
        return extractFieldValue(source, "next", String.class);
    }

    /**
     * Retrieve the URI of the previous page of results (if any) for the query from the JSON message.
     *
     * @param source JSON response from freesound
     * @return Previous page URI
     */
    public String extractPreviousPageURI(final JSONObject source) {
        return extractFieldValue(source, "previous", String.class);
    }
}