com.google.enterprise.connector.util.diffing.OrderedSnapshotWriter.java Source code

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Here is the source code for com.google.enterprise.connector.util.diffing.OrderedSnapshotWriter.java

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// Copyright 2013 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.enterprise.connector.util.diffing;

import static com.google.enterprise.connector.util.diffing.DocumentSnapshotComparator.COMPARATOR;

import com.google.common.io.NullOutputStream;

import java.io.OutputStreamWriter;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * A wrapper on the SnapshotWriter that enforces an ordering on the
 * written snapshots, to prevent duplicates being written to the
 * store. This is slightly hacky because SnapshotWriter is a concrete
 * implementation rather than an interface.
 */
class OrderedSnapshotWriter extends SnapshotWriter {
    private static final Logger LOG = Logger.getLogger(OrderedSnapshotWriter.class.getName());

    private final SnapshotWriter delegate;

    /** The largest document snapshot we have seen. */
    private DocumentSnapshot maxWrittenSnapshot;

    public OrderedSnapshotWriter(SnapshotWriter delegate) throws SnapshotWriterException {
        // The superclass is not actually used, but the Writer argument
        // cannot be null. We use a null sink.
        super(new OutputStreamWriter(new NullOutputStream()), null, null);
        this.delegate = delegate;
        this.maxWrittenSnapshot = null;
    }

    @Override
    public void write(DocumentSnapshot snapshot) throws SnapshotWriterException, IllegalArgumentException {
        if (maxWrittenSnapshot == null || COMPARATOR.compare(snapshot, maxWrittenSnapshot) > 0) {
            maxWrittenSnapshot = snapshot;
            delegate.write(snapshot);
        } else {
            LOG.log(Level.WARNING, "Processed out of order document snapshot {0}, " + "not writing to store.",
                    snapshot.getDocumentId());
        }
    }

    @Override
    public void close() throws SnapshotWriterException {
        delegate.close();
    }

    @Override
    public String getPath() {
        return delegate.getPath();
    }

    @Override
    public long getRecordCount() {
        return delegate.getRecordCount();
    }
}