BlobstoreBlobService.java

package org.activityinfo.server.util.blob;

import com.google.appengine.api.blobstore.BlobKey;
import com.google.appengine.api.blobstore.BlobstoreInputStream;
import com.google.appengine.api.datastore.*;
import com.google.appengine.api.files.AppEngineFile;
import com.google.appengine.api.files.FileService;
import com.google.appengine.api.files.FileServiceFactory;
import com.google.appengine.api.files.FileWriteChannel;
import com.google.common.io.ByteStreams;
import com.google.common.io.InputSupplier;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.channels.Channels;

public class BlobstoreBlobService implements BlobService {

    private FileService fileService = FileServiceFactory.getFileService();
    private DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();

    @Override
    public void put(String key, InputSupplier<? extends InputStream> blob) throws IOException {

        OutputStream out = put(key);
        ByteStreams.copy(blob, out);
        out.close();
    }

    @Override
    public OutputStream put(final String key) throws IOException {
        final AppEngineFile file = fileService.createNewBlobFile("application/octet-stream");
        boolean lock = true;
        final FileWriteChannel writeChannel = fileService.openWriteChannel(file, lock);
        final OutputStream os = Channels.newOutputStream(writeChannel);

        return new DelegatingOutputStream(os) {

            @Override
            protected void afterClosed() throws IOException {
                try {
                    writeChannel.closeFinally();
                } catch (IOException e) {
                    throw e;
                } catch (Exception e) {
                    throw new IOException(e);
                }

                Entity entity = new Entity("Blob", key);
                entity.setUnindexedProperty("blobKey", fileService.getBlobKey(file));
                datastore.put(entity);
            }
        };
    }

    @Override
    public InputSupplier<InputStream> get(String key) throws BlobNotFoundException {
        Entity entity;
        try {
            entity = datastore.get(KeyFactory.createKey("Blob", key));
        } catch (EntityNotFoundException e) {
            throw new BlobNotFoundException();
        }

        final BlobKey blobKey = (BlobKey) entity.getProperty("blobKey");

        return new InputSupplier<InputStream>() {
            @Override
            public InputStream getInput() throws IOException {
                return new BlobstoreInputStream(blobKey);
            }
        };
    }

}