hadoop - 获取空指针异常

Question

目前我正在尝试学习 map reduce 中的二级排序，但在运行我的映射器时出现空指针异常错误。我正在使用这个 link 但是在运行代码时出现错误。这是我的 callStack。

16/06/18 13:34:53 INFO mapreduce.Job: Task Id : attempt_1466235357420_0007_m_000000_0, Status : FAILED Error: java.lang.NullPointerException at SecondartSort.SecondarySortSample1.SecondarySortMapper.map(SecondarySortMapper.java:22) at SecondartSort.SecondarySortSample1.SecondarySortMapper.map(SecondarySortMapper.java:1) at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:145) at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:784) at org.apache.hadoop.mapred.MapTask.run(MapTask.java:341) at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:163) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:415)

我的映射器代码是:

public class SecondarySortMapper  extends Mapper<LongWritable , Text, CustomTextInt, IntWritable> {

    private CustomTextInt nameDepname;
    private Text name;
    private Text departmentName;
    private IntWritable sal;
    public void map (LongWritable key , Text value , Context context) throws IOException , InterruptedException{

        String[] line = value.toString().split(",");

        //String depName = line[3];
        String Fullname =line[2]+line[1];
        name.set(Fullname);
        departmentName.set(line[3]);
        nameDepname.set(name,departmentName);
        sal.set(Integer.parseInt(line[4]));
        context.write(nameDepname, sal);    
    }
}

数据文件是:

1,kumar,sunil,enginering,2200
2,mishra,sunil,enginering,1200
3,arora,karan,mech,1200
4,sharma,vivek,physics,2300
5,koushik,vivek,physics,1350
6,sindhu,armaan,math,2310
7,arora,armaan,math,500
8,yadav,pooja,mech,1800
9,kuthi,pooja,math,1600
10,arora,sunil,physics,1450
11,mishra,karan,enginering,3400
12,chandra,manish,physics,2300

请多多指教

谢谢普拉迪普

Answer 1

您实际上并没有创建任何类变量。这些都将是未初始化的:

private CustomTextInt nameDepname;
private Text name;
private Text departmentName;
private IntWritable sal;

例如 name 应该是这样的:

private Text name = new Text();