如何在Hadoop中使用自定义类型

import org.apache.hadoop.io.Writable;

public class CustomType implements Writable {
    // 实现write方法以将对象序列化为字节流
    public void write(DataOutput out) throws IOException {
        // 将对象的字段写入输出流
        out.writeInt(field1);
        out.writeDouble(field2);
        // ...
    }

    // 实现readFields方法以从字节流中反序列化对象
    public void readFields(DataInput in) throws IOException {
        // 从输入流中读取字段并设置对象的值
        field1 = in.readInt();
        field2 = in.readDouble();
        // ...
    }
}

import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

public class MyMapper extends Mapper<LongWritable, Text, CustomType, Text> {
    private CustomType customKey = new CustomType();
    private Text outputValue = new Text();

    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        // 设置自定义类型对象的值
        customKey.setField1(123);
        customKey.setField2(3.14);
        // ...

        // 发出键值对
        context.write(customKey, outputValue);
    }
}

Configuration conf = new Configuration();
conf.set("io.serializations", "org.apache.hadoop.io.serializer.WritableSerialization,com.example.CustomType");