WritableComparable排序
排序概述
排序分类
自定义排序WritableComparable原理分析
bean对象做为key传输,需要实现WritableComparable接口重写compareTo方法,就可以实现排序。
@Override
public int compareTo(FlowBean bean) {
int result;
// 按照总流量大小,倒序排列
if (this.sumFlow > bean.getSumFlow()) {
result = -1;
}else if (this.sumFlow < bean.getSumFlow()) {
result = 1;
}else {
result = 0;
}
return result;
}
WritableComparable排序案例实操(全排序)
1)需求
根据案例2.3序列化案例产生的结果再次对总流量进行倒序排序。
(1)输入数据
原始数据:第一次处理后的数据part-r-00000
(2)期望输出数据
13509468723 7335 110349 117684
13736230513 2481 24681 27162
13956435636 132 1512 1644
13846544121 264 0 264
。。。 。。
2)需求分析
3)代码实现
(1)FlowBean对象在在需求1基础上增加了比较功能
import org.apache.hadoop.io.WritableComparable;
public class FlowBean implements WritableComparable<FlowBean> {
private long upFlow;
private long downFlow;
private long sumFlow;
// 反序列化时,需要反射调用空参构造函数,所以必须有
public FlowBean() {
}
// 序列化方法
@Override
public void write(DataOutput out) throws IOException {
out.writeLong(upFlow);
out.writeLong(downFlow);
out.writeLong(sumFlow);
}
// 反序列化方法 注意反序列化的顺序和序列化的顺序完全一致
@Override
public void readFields(DataInput in) throws IOException {
upFlow = in.readLong();
downFlow = in.readLong();
sumFlow = in.readLong();
}
@Override
public String toString() {
return upFlow + "\t" + downFlow + "\t" + sumFlow;
}
@Override
public int compareTo(FlowBean bean) {
int result;
// 按照总流量大小,倒序排列
if (sumFlow > bean.getSumFlow()) result = -1;
else if (sumFlow < bean.getSumFlow()) result = 1;
else result = 0;
return result;
}
}
(2)编写Mapper类
public class FlowCountSortMapper extends Mapper<LongWritable, Text, FlowBean, Text>{
FlowBean bean = new FlowBean();
Text v = new Text();
@Override
protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
// 1 获取一行
String line = value.toString();
// 2 截取
String[] fields = line.split("\t");
// 3 封装对象
String phoneNbr = fields[0];
long upFlow = Long.parseLong(fields[1]);
long downFlow = Long.parseLong(fields[2]);
bean.set(upFlow, downFlow);
v.set(phoneNbr);
// 4 输出
context.write(bean, v);
}
}
(3)编写Reducer类
public class FlowCountSortReducer extends Reducer<FlowBean, Text, Text, FlowBean>{
@Override
protected void reduce(FlowBean key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
// 循环输出,避免总流量相同情况
for (Text text : values) {
context.write(text, key);
}
}
}
(4)编写Driver类
public class FlowCountSortDriver {
public static void main(String[] args) throws ClassNotFoundException, IOException, InterruptedException {
// 输入输出路径需要根据自己电脑上实际的输入输出路径设置
args = new String[]{"e:/output","e:/output"};
// 1 获取配置信息,或者job对象实例
Configuration configuration = new Configuration();
Job job = Job.getInstance(configuration);
// 2 指定本程序的jar包所在的本地路径
job.setJarByClass(FlowCountSortDriver.class);
// 3 指定本业务job要使用的mapper/Reducer业务类
job.setMapperClass(FlowCountSortMapper.class);
job.setReducerClass(FlowCountSortReducer.class);
// 4 指定mapper输出数据的kv类型
job.setMapOutputKeyClass(FlowBean.class);
job.setMapOutputValueClass(Text.class);
// 5 指定最终输出的数据的kv类型
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(FlowBean.class);
// 6 指定job的输入原始文件所在目录
FileInputFormat.setInputPaths(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
// 7 将job中配置的相关参数,以及job所用的java类所在的jar包, 提交给yarn去运行
boolean result = job.waitForCompletion(true);
System.exit(result ? 0 : 1);
}
}
WritableComparable排序案例实操(区内排序)
1)需求
要求每个省份手机号输出的文件中按照总流量内部排序。
2)需求分析
基于前一个需求,增加自定义分区类,分区按照省份手机号设置。
3)案例实操
(1)增加自定义分区类
public class ProvincePartitioner extends Partitioner<FlowBean, Text> {
@Override
public int getPartition(FlowBean key, Text value, int numPartitions) {
// 1 获取手机号码前三位
String preNum = value.toString().substring(0, 3);
int partition = 4;
// 2 根据手机号归属地设置分区
if ("136".equals(preNum)) {
partition = 0;
}else if ("137".equals(preNum)) {
partition = 1;
}else if ("138".equals(preNum)) {
partition = 2;
}else if ("139".equals(preNum)) {
partition = 3;
}
return partition;
}
}
(2)在驱动类中添加分区类
// 加载自定义分区类
job.setPartitionerClass(ProvincePartitioner.class);
// 设置Reducetask个数
job.setNumReduceTasks(5);