Example of static helpers to convert to and from InputStreams

DocumentToBinary.java

package example;

import org.bson.BsonBinaryReader;
import org.bson.BsonBinaryWriter;
import org.bson.Document;
import org.bson.codecs.Codec;
import org.bson.codecs.DecoderContext;
import org.bson.codecs.DocumentCodec;
import org.bson.codecs.EncoderContext;
import org.bson.io.BasicOutputBuffer;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;

import static java.util.Arrays.asList;

public class DocumentToBinary {
    private static Codec<Document> DOCUMENT_CODEC = new DocumentCodec();

    public static void main(final String[] args) {
        Document myDocument = new Document("_id", 1).append("key1", asList(1, 2, 3, 4));

        try {
            Document myCopiedDocument = fromInputStream(toInputStream(myDocument));
            assert myCopiedDocument.equals(myDocument);
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    public static InputStream toInputStream(final Document document) {
        BasicOutputBuffer outputBuffer = new BasicOutputBuffer();
        BsonBinaryWriter writer = new BsonBinaryWriter(outputBuffer);
        DOCUMENT_CODEC.encode(writer, document, EncoderContext.builder().isEncodingCollectibleDocument(true).build());
        return new ByteArrayInputStream(outputBuffer.toByteArray());
    }

    public static Document fromInputStream(final InputStream input) throws IOException {
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        int len;
        while ((len = input.read(buffer)) != -1) {
            outputStream.write(buffer, 0, len);
        }
        outputStream.close();
        BsonBinaryReader bsonReader = new BsonBinaryReader(ByteBuffer.wrap(outputStream.toByteArray()));
        return DOCUMENT_CODEC.decode(bsonReader, DecoderContext.builder().build());
    }
}