MapReduce自定义排序器不生效一个可能的原因

Posted 2021-12-01 144823836yj

有问题的代码：

package com.mytq.weather;

import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableComparator;


public class WSortComparator extends WritableComparator {

    public WSortComparator() {
        super(Weather.class, true);
    }


    @Override
    public int compare(Object a, Object b) { //使用object会有问题

        Weather t1 = (Weather)a;
        Weather t2 = (Weather)b;
        
        int c1 = Integer.compare(t1.getYear(), t2.getYear());
        if (c1 == 0) {
            int c2 = Integer.compare(t1.getMonth(), t2.getMonth());
            
            if (c2==0) {
                return -Integer.compare(t1.getWd(), t2.getWd()); // 温度倒序排列
            }
            
            returnreturn c1;
    }
}

需要将compare两个参数的类型由object修改为WritableComparable才行。

 

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在源码中暂时没找到调用逻辑┓( ´∀` )┏