com.talvish.tales.serialization.json.translators.ArrayToJsonArrayTranslator.java Source code

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Here is the source code for com.talvish.tales.serialization.json.translators.ArrayToJsonArrayTranslator.java

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// ***************************************************************************
// *  Copyright 2012 Joseph Molnar
// *
// *  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.talvish.tales.serialization.json.translators;

import java.lang.reflect.Array;

import com.google.common.base.Preconditions;
import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonNull;
import com.talvish.tales.parts.translators.TranslationException;
import com.talvish.tales.parts.translators.Translator;

/**
 * Translator that converts a collection into a json array,
 * or, if null, {@code JsonNull}.
 * @author jmolnar
 *
 */
public class ArrayToJsonArrayTranslator implements Translator {
    private final Translator elementTranslator;
    private final boolean writeSingle;

    /**
     * Constructor taking the element translator.
     * There is no special handling of single element arrays.
     * @param theElementTranslator the translator to use on the elements
     */
    public ArrayToJsonArrayTranslator(Translator theElementTranslator) {
        this(theElementTranslator, false);
    }

    /**
     * Constructor taking the element translator and indication of 
     * special handling of a single element array.
     * @param theElementTranslator the translator to use on the elements
     * @param writeSingle true means that if there is a single element it isn't written as an array but as the object
     */
    public ArrayToJsonArrayTranslator(Translator theElementTranslator, boolean writeSingle) {
        Preconditions.checkNotNull(theElementTranslator);

        elementTranslator = theElementTranslator;
        this.writeSingle = writeSingle;
    }

    /**
     * Translates the received object into a json array.
     * If the object is of the wrong type, a TranslationException will occur.
     */
    @Override
    public Object translate(Object anObject) {
        Object returnValue;

        if (anObject == null) {
            returnValue = JsonNull.INSTANCE;
        } else {
            try {
                if (anObject.getClass().isArray()) {
                    int arrayLength = Array.getLength(anObject);
                    if (arrayLength != 1 || !writeSingle) {
                        JsonArray jsonArray = new JsonArray();
                        for (int count = 0; count < arrayLength; count += 1) {
                            jsonArray.add((JsonElement) elementTranslator.translate(Array.get(anObject, count)));
                        }
                        returnValue = jsonArray;
                    } else {
                        // this happens we are allowing the single item arrays to be written out as a non-array
                        returnValue = (JsonElement) elementTranslator.translate(Array.get(anObject, 0));
                    }
                } else {
                    throw new TranslationException(String.format(
                            "Received a '%s' instead of an array, so unable to translate into a json array.",
                            anObject.getClass().getName()));
                }
            } catch (ClassCastException e) {
                throw new TranslationException(e);
            }
        }
        return returnValue;
    }
}