用Java编写MapReduce对2月 商品A 325 1月 商品A 235 1月 商品B 234 2月 商品C 572 3月 商品A 123 1月 商品C 321 2月 商品B 573 3月 商品C 876进行排序,要求先按月份升序排序,再按销售量降序排序,结果输出的是:1月 商品C 321 1月 商品A 235 1月 商品B 234 2月 商品B 573 2月 商品C 572 2月 商品A 325 3月 商品C 876 3月 商品B 648 3月 商品A 123
时间: 2024-01-07 10:06:04 浏览: 58
首先,需要定义一个自定义的Writable类型用于存储每个输入记录的月份、商品名称和销售量。代码如下:
```java
public class SalesRecord implements WritableComparable<SalesRecord> {
private Text month;
private Text product;
private IntWritable sales;
public SalesRecord() {
month = new Text();
product = new Text();
sales = new IntWritable();
}
public SalesRecord(String month, String product, int sales) {
this.month = new Text(month);
this.product = new Text(product);
this.sales = new IntWritable(sales);
}
public void write(DataOutput out) throws IOException {
month.write(out);
product.write(out);
sales.write(out);
}
public void readFields(DataInput in) throws IOException {
month.readFields(in);
product.readFields(in);
sales.readFields(in);
}
public int compareTo(SalesRecord other) {
int cmp = month.compareTo(other.month);
if (cmp != 0) {
return cmp;
}
return -sales.compareTo(other.sales);
}
public Text getMonth() {
return month;
}
public Text getProduct() {
return product;
}
public IntWritable getSales() {
return sales;
}
public void set(String month, String product, int sales) {
this.month = new Text(month);
this.product = new Text(product);
this.sales = new IntWritable(sales);
}
public String toString() {
return month + " " + product + " " + sales;
}
}
```
然后,需要编写Mapper和Reducer类。Mapper类将每个输入记录解析为一个SalesRecord对象,并将其输出。Reducer类将所有具有相同月份的SalesRecords收集在一起,并对它们按销售量进行排序。代码如下:
```java
public class SalesSorter {
public static class SalesMapper extends Mapper<Object, Text, SalesRecord, NullWritable> {
private SalesRecord salesRecord = new SalesRecord();
public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
String[] fields = value.toString().split(" ");
salesRecord.set(fields[1], fields[2], Integer.parseInt(fields[3]));
context.write(salesRecord, NullWritable.get());
}
}
public static class SalesReducer extends Reducer<SalesRecord, NullWritable, SalesRecord, NullWritable> {
public void reduce(SalesRecord key, Iterable<NullWritable> values, Context context) throws IOException, InterruptedException {
for (NullWritable value : values) {
context.write(key, NullWritable.get());
}
}
}
}
```
最后,需要在main函数中配置MapReduce作业,并运行它。代码如下:
```java
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
Job job = Job.getInstance(conf, "sales sort");
job.setJarByClass(SalesSorter.class);
job.setMapperClass(SalesMapper.class);
job.setReducerClass(SalesReducer.class);
job.setMapOutputKeyClass(SalesRecord.class);
job.setMapOutputValueClass(NullWritable.class);
job.setOutputKeyClass(SalesRecord.class);
job.setOutputValueClass(NullWritable.class);
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
```
将以上所有代码保存为一个Java文件并编译运行,就可以得到按月份升序排序、按销售量降序排序的结果。
阅读全文