org.apache.flume.serialization.EventDeserializer Maven / Gradle / Ivy
/**
* 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.apache.flume.serialization;
import java.io.Closeable;
import java.io.IOException;
import java.util.List;
import org.apache.flume.Context;
import org.apache.flume.Event;
import org.apache.flume.annotations.InterfaceAudience;
import org.apache.flume.annotations.InterfaceStability;
/**
* Establishes a contract for reading events stored in arbitrary formats from
* reliable, resettable streams.
*/
@InterfaceAudience.Public
@InterfaceStability.Evolving
public interface EventDeserializer extends Resettable, Closeable {
/**
* Read a single event from the underlying stream.
* @return Deserialized event or {@code null} if no events could be read.
* @throws IOException
* @see #mark()
* @see #reset()
*/
public Event readEvent() throws IOException;
/**
* Read a batch of events from the underlying stream.
* @param numEvents Maximum number of events to return.
* @return List of read events, or empty list if no events could be read.
* @throws IOException
* @see #mark()
* @see #reset()
*/
public List readEvents(int numEvents) throws IOException;
/**
* Marks the underlying input stream, indicating that the events previously
* returned by this EventDeserializer have been successfully committed.
* @throws IOException
* @see #reset()
*/
@Override
public void mark() throws IOException;
/**
* Resets the underlying input stream to the last known mark (or beginning
* of the stream if {@link #mark()} was never previously called. This should
* be done in the case of inability to commit previously-deserialized events.
* @throws IOException
* @see #mark()
*/
@Override
public void reset() throws IOException;
/**
* Calls {@link #reset()} on the stream and then closes it.
* In the case of successful completion of event consumption,
* {@link #mark()} MUST be called before {@code close()}.
* @throws IOException
* @see #mark()
* @see #reset()
*/
@Override
public void close() throws IOException;
/**
* Knows how to construct this deserializer.
* Note: Implementations MUST provide a public a no-arg constructor.
*/
public interface Builder {
public EventDeserializer build(Context context, ResettableInputStream in);
}
}