Writable.java
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上传日期:2018-01-08
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文件大小:3k
- /**
- * 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.hadoop.io;
- import java.io.DataOutput;
- import java.io.DataInput;
- import java.io.IOException;
- /**
- * A serializable object which implements a simple, efficient, serialization
- * protocol, based on {@link DataInput} and {@link DataOutput}.
- *
- * <p>Any <code>key</code> or <code>value</code> type in the Hadoop Map-Reduce
- * framework implements this interface.</p>
- *
- * <p>Implementations typically implement a static <code>read(DataInput)</code>
- * method which constructs a new instance, calls {@link #readFields(DataInput)}
- * and returns the instance.</p>
- *
- * <p>Example:</p>
- * <p><blockquote><pre>
- * public class MyWritable implements Writable {
- * // Some data
- * private int counter;
- * private long timestamp;
- *
- * public void write(DataOutput out) throws IOException {
- * out.writeInt(counter);
- * out.writeLong(timestamp);
- * }
- *
- * public void readFields(DataInput in) throws IOException {
- * counter = in.readInt();
- * timestamp = in.readLong();
- * }
- *
- * public static MyWritable read(DataInput in) throws IOException {
- * MyWritable w = new MyWritable();
- * w.readFields(in);
- * return w;
- * }
- * }
- * </pre></blockquote></p>
- */
- public interface Writable {
- /**
- * Serialize the fields of this object to <code>out</code>.
- *
- * @param out <code>DataOuput</code> to serialize this object into.
- * @throws IOException
- */
- void write(DataOutput out) throws IOException;
- /**
- * Deserialize the fields of this object from <code>in</code>.
- *
- * <p>For efficiency, implementations should attempt to re-use storage in the
- * existing object where possible.</p>
- *
- * @param in <code>DataInput</code> to deseriablize this object from.
- * @throws IOException
- */
- void readFields(DataInput in) throws IOException;
- }