org.sejda.sambox.output.AsyncPDFBodyObjectsWriter Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of sambox Show documentation
An Apache PDFBox fork intended to be used as PDF processor for Sejda and PDFsam related projects
There is a newer version: 3.0.21
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.sejda.sambox.output;

import static org.sejda.commons.util.RequireUtils.requireNotNullArg;

import java.io.IOException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicReference;

import org.sejda.sambox.cos.IndirectCOSObjectReference;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Implementation of a PDFBodyObjectsWriter that asynchronously writes {@link IndirectCOSObjectReference}. Objects are
 * written submitting a task to a single thread executor service.
 * 
 * @author Andrea Vacondio
 *
 */
class AsyncPDFBodyObjectsWriter implements PDFBodyObjectsWriter
{

    private static final Logger LOG = LoggerFactory.getLogger(AsyncPDFBodyObjectsWriter.class);

    private final ExecutorService executor = Executors.newSingleThreadExecutor(
            target -> new Thread(null, target, "pdf-writer-thread", 0));
    private final AtomicReference executionException = new AtomicReference<>();
    private final IndirectObjectsWriter writer;

    AsyncPDFBodyObjectsWriter(IndirectObjectsWriter writer)
    {
        requireNotNullArg(writer, "Cannot write to a null writer");
        this.writer = writer;
    }

    @Override
    public void writeObject(IndirectCOSObjectReference ref) throws IOException
    {
        assertCanSubmitAsyncTask();
        executor.execute(() -> {
            try
            {
                if (executionException.get() == null)
                {
                    writer.writeObjectIfNotWritten(ref);
                }
            }
            catch (IOException e)
            {
                executionException.set(e);
            }
            catch (Exception e)
            {
                executionException.set(new IOException(e));
            }
        });
    }

    private void assertCanSubmitAsyncTask() throws IOException
    {
        IOException previous = executionException.get();
        if (previous != null)
        {
            executor.shutdownNow();
            throw previous;
        }
    }

    @Override
    public void onWriteCompletion() throws IOException
    {
        assertCanSubmitAsyncTask();
        try
        {
            executor.submit(() -> {
                IOException previous = executionException.get();
                if (previous != null)
                {
                    throw previous;
                }
                LOG.debug("Written document body");
                return null;
            }).get();
        }
        catch (InterruptedException e)
        {
            throw new IOException(e);
        }
        catch (ExecutionException e)
        {
            throw new IOException(e.getCause());
        }

    }

    @Override
    public void close()
    {
        executor.shutdown();
    }
}