hadoop自定义序列化

hadoop的MR中的m和r阶段的kv键值对都需要实现序列化，hadoop自带的Text，LongWriable...等，有时候需要自定义java数据类型作为key value，下面实现一个最简单的序列化实现。

package Test;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import org.apache.hadoop.io.Writable;
public class TestWritable implements Writable{
long id = 0L;
public TestWritable(){
super();
}
public TestWritable(long id){
super();
this.id = id;
}
@Override
public void write(DataOutput out) throws IOException {
out.writeLong(id);
}
@Override
public void readFields(DataInput in) throws IOException {
this.id = in.readLong();
}
@Override
public String toString() {
return ""+id;
}
}