编辑“︁Apache Hadoop数据序列化”︁（章节）

== Hadoop Writable 示例 ==
Hadoop原生使用<code>Writable</code>接口实现序列化。以下是自定义Writable类的示例：

<syntaxhighlight lang="java">
import org.apache.hadoop.io.Writable;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

public class SensorReading implements Writable {
    private String sensorId;
    private double temperature;
    
    // 反序列化方法
    @Override
    public void readFields(DataInput in) throws IOException {
        this.sensorId = in.readUTF();
        this.temperature = in.readDouble();
    }
    
    // 序列化方法
    @Override
    public void write(DataOutput out) throws IOException {
        out.writeUTF(sensorId);
        out.writeDouble(temperature);
    }
    
    // 其他getter/setter方法省略
}
</syntaxhighlight>

'''使用示例'''：
<syntaxhighlight lang="java">
SensorReading reading = new SensorReading("sensor-001", 28.5);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(baos);
reading.write(dos);  // 序列化

byte[] serializedData = baos.toByteArray();

// 反序列化过程
DataInputStream dis = new DataInputStream(new ByteArrayInputStream(serializedData));
SensorReading newReading = new SensorReading();
newReading.readFields(dis);
</syntaxhighlight>