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

Introduction

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

Source

/*
 * 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.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.TimeZone;

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

/**
 * Abstract class defining common functionality required when converting objects of different types. In general, this
 * means JSON objects received from calls to the freesound.org API into the DTOs returned by this library.
 *
 * @param <S> The source type we are converting from
 * @param <R> The type we are converting to
 */
public abstract class Mapper<S extends Object, R extends Object> {

    /** The date/time format used by freesound. */
    private static final String FREESOUND_DATE_FORMAT = "yyyy-MM-dd'T'HH:mm:ss";

    /**
     * Perform the conversion between the two specified types.
     *
     * @param source The object we are converting from
     * @return The converted object
     */
    public abstract R map(S source);

    /**
     * Extract a named value from a {@link JSONObject}. This method checks whether the value exists and is not an
     * instance of <code>JSONObject.NULL</code>.
     *
     * @param jsonObject The {@link JSONObject} being processed
     * @param field The field to retrieve
     * @param fieldType The data type of the field
     * @return The field value (or null if not found)
     *
     * @param <T> The data type to return
     */
    @SuppressWarnings("unchecked")
    protected <T extends Object> T extractFieldValue(final JSONObject jsonObject, final String field,
            final Class<T> fieldType) {
        T fieldValue = null;
        if ((jsonObject != null) && jsonObject.has(field) && !jsonObject.isNull(field)) {
            try {
                if (fieldType == String.class) {
                    fieldValue = (T) jsonObject.getString(field);
                } else if (fieldType == Integer.class) {
                    fieldValue = (T) Integer.valueOf(jsonObject.getInt(field));
                } else if (fieldType == Long.class) {
                    fieldValue = (T) Long.valueOf(jsonObject.getLong(field));
                } else if (fieldType == Float.class) {
                    fieldValue = (T) Float.valueOf(Double.toString(jsonObject.getDouble(field)));
                } else if (fieldType == JSONArray.class) {
                    fieldValue = (T) jsonObject.getJSONArray(field);
                } else if (fieldType == JSONObject.class) {
                    fieldValue = (T) jsonObject.getJSONObject(field);
                } else {
                    fieldValue = (T) jsonObject.get(field);
                }
            } catch (final JSONException | ClassCastException e) {
                // TODO Log a warning
            }
        }

        return fieldValue;
    }

    /**
     * Transform a JSON dictionary into a {@link Map} of key-value pairs.
     *
     * @param jsonDictionaryObject The dictionary object to convert
     * @return {@link Map} of values
     */
    protected Map<String, String> parseDictionary(final JSONObject jsonDictionaryObject) {
        final Map<String, String> dictionaryAsMap = new HashMap<>();
        if (jsonDictionaryObject != null) {
            for (final String key : JSONObject.getNames(jsonDictionaryObject)) {
                dictionaryAsMap.put(key, extractFieldValue(jsonDictionaryObject, key, String.class));
            }
        }

        return dictionaryAsMap;
    }

    /**
     * Transform a JSON Array into a {@link List}.
     *
     * @param jsonArray The {@link JSONArray} to convert
     * @return List of values
     */
    protected List<String> parseArray(final JSONArray jsonArray) {
        final List<String> arrayContents = new ArrayList<>();

        if (jsonArray != null) {
            for (int i = 0; i < jsonArray.length(); i++) {
                final String element = jsonArray.getString(i);
                if (element != null) {
                    arrayContents.add(element);
                }
            }
        }

        return arrayContents;
    }

    /**
     * Transform an array of JSON Objects into a {@link List} of DTOs.
     *
     * @param <T> The object type contained with in the array
     *
     * @param jsonArray The {@link JSONArray} to convert
     * @param objectMapper The {@link Mapper} to use to process the JSON objects
     *
     * @return List of DTOs
     */
    protected <T extends Object> List<T> parseArray(final JSONArray jsonArray,
            final Mapper<JSONObject, T> objectMapper) {
        final List<T> arrayContents = new ArrayList<>();

        if (jsonArray != null) {
            for (int i = 0; i < jsonArray.length(); i++) {
                final JSONObject element = jsonArray.getJSONObject(i);
                if (element != null) {
                    arrayContents.add(objectMapper.map(element));
                }
            }
        }

        return arrayContents;
    }

    /**
     * Parse a date from a {@link String} to a {@link Date} object, assuming the freesound standard format.
     *
     * @param dateString The string to convert
     * @return {@link Date} representation
     */
    protected Date parseDate(final String dateString) {
        Date date = null;
        if (dateString != null) {
            try {
                final SimpleDateFormat dateFormat = new SimpleDateFormat(FREESOUND_DATE_FORMAT);
                dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));

                date = dateFormat.parse(dateString);
            } catch (final ParseException e) {
                // TODO Log a warning
            }
        }

        return date;
    }
}