com.google.cloud.dataflow.sdk.runners.worker.DataflowApiUtils.java Source code

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/*******************************************************************************
 * Copyright (C) 2016 Google Inc.
 *
 * 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.google.cloud.dataflow.sdk.runners.worker;

import com.google.api.client.json.GenericJson;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.JsonGenerator;
import com.google.cloud.dataflow.sdk.util.Transport;
import com.google.common.io.ByteStreams;
import com.google.common.io.CountingOutputStream;

import java.io.IOException;
import java.nio.charset.StandardCharsets;

/**
 * A utility class for generic interactions with the Google Cloud Dataflow API.
 */
public final class DataflowApiUtils {
    /**
     * Determines the serialized size (in bytes) of the {@link GenericJson} object that will be
     * serialized and sent to the Google Cloud Dataflow service API.
     *
     * <p>Uses only constant memory.
     */
    public static long computeSerializedSizeBytes(GenericJson object) throws IOException {
        JsonFactory factory = object.getFactory();
        if (factory == null) {
            factory = Transport.getJsonFactory();
        }

        CountingOutputStream stream = new CountingOutputStream(ByteStreams.nullOutputStream());
        JsonGenerator generator = null;
        try {
            generator = factory.createJsonGenerator(stream, StandardCharsets.UTF_8);
            generator.serialize(object);
            generator.close(); // also closes the stream.
        } finally {
            if (generator != null) {
                generator.close();
            }
        }
        return stream.getCount();
    }

    // Prevent construction of utility class.
    private DataflowApiUtils() {
    }
}