Hadoop入门到精通：MapReduce高级操作——对象排序

//对象类：Employee.java，实现WritableComparable接口，重写compareTo()方法
package demo.sort.mr.object;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import org.apache.hadoop.io.WritableComparable;
//实现接口：WritableComparable
public class Employee implements WritableComparable<Employee> {
  private int empno;
  private String ename;
  private String job;
  private int mgr;
  private String hiredate;
  private int sal;
  private int comm;
  private int deptno;
  @Override
  public String toString() {
    return "[" + this.ename + "\t" + this.sal + "]";
  }
  @Override
  public int compareTo(Employee other) {
    // 按工资降序排列
    if (this.sal >= other.getSal()) {
      return -1;
    } else {
      return 1;
    }
  }
  @Override
  public void readFields(DataInput input) throws IOException {
    // 反序列化
    this.empno = input.readInt();
    this.ename = input.readUTF();
    this.job = input.readUTF();
    this.mgr = input.readInt();
    this.hiredate = input.readUTF();
    this.sal = input.readInt();
    this.comm = input.readInt();
    this.deptno = input.readInt();
  }
  @Override
  public void write(DataOutput output) throws IOException {
    // 序列化
    output.writeInt(this.empno);
    output.writeUTF(this.ename);
    output.writeUTF(this.job);
    output.writeInt(this.mgr);
    output.writeUTF(this.hiredate);
    output.writeInt(this.sal);
    output.writeInt(this.comm);
    output.writeInt(this.deptno);
  }
  public int getEmpno() {
    return empno;
  }
  public void setEmpno(int empno) {
    this.empno = empno;
  }
  public String getEname() {
    return ename;
  }
  public void setEname(String ename) {
    this.ename = ename;
  }
  public String getJob() {
    return job;
  }
  public void setJob(String job) {
    this.job = job;
  }
  public int getMgr() {
    return mgr;
  }
  public void setMgr(int mgr) {
    this.mgr = mgr;
  }
  public String getHiredate() {
    return hiredate;
  }
  public void setHiredate(String hiredate) {
    this.hiredate = hiredate;
  }
  public int getSal() {
    return sal;
  }
  public void setSal(int sal) {
    this.sal = sal;
  }
  public int getComm() {
    return comm;
  }
  public void setComm(int comm) {
    this.comm = comm;
  }
  public int getDeptno() {
    return deptno;
  }
  public void setDeptno(int deptno) {
    this.deptno = deptno;
  }
}

//Mapper文件：EmployeeSortMapper.java
package demo.sort.mr.object;
import java.io.IOException;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
public class EmployeeSortMapper extends Mapper<LongWritable, Text, Employee, NullWritable> {
  @Override
  protected void map(LongWritable key1, Text value1, Context context) 
      throws IOException, InterruptedException {
    // 把读入的数据封装成一个员工对象
    // 数据格式：7654,MARTIN,SALESMAN,7698,1981/9/28,1250,1400,30
    String str = value1.toString();
    // 分词
    String[] words = str.split(",");
    // 创建一个员工对象
    Employee e = new Employee();
    // 设置员工的属性
    e.setEmpno(Integer.parseInt(words[0]));
    e.setEname(words[1]);
    e.setJob(words[2]);
    try {
      e.setMgr(Integer.parseInt(words[3]));
    } catch (Exception ex) {
      e.setMgr(0);
    }
    e.setHiredate(words[4]);
    e.setSal(Integer.parseInt(words[5]));
    try {
      e.setComm(Integer.parseInt(words[6]));
    } catch (Exception ex) {
      e.setComm(0);
    }
    e.setDeptno(Integer.parseInt(words[7]));
    // 输出：员工对象，null
    context.write(e, NullWritable.get());
  }
}
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