hadoop Writable 源码
haddop Writable 代码
文件路径：/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/Writable.java
/**
* 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;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
/**
* 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>
* <blockquote><pre>
* public class MyWritable implements Writable {
* // Some data
* private int counter;
* private long timestamp;
*
* // Default constructor to allow (de)serialization
* MyWritable() { }
*
* 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>
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
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 any other problem for write.
*/
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 any other problem for readFields.
*/
void readFields(DataInput in) throws IOException;
}
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