利用hadoop命令rcc生成Record 一种简单的方式实现自定义的writable对象，hadoopwritable

利用hadoop命令rcc生成Record 一种简单的方式实现自定义的writable对象，hadoopwritable

 
hadoop 的bin目录下面一个rcc命令，网上介绍很少。看了一下源码。发现可以用来生成 java和c++的hadoop Record 类代码，比起自己直接实现writable 接口，简单很多而且不容易出错，不妨试一下。具体方法如下：

>rccUsage: rcc --language [java|c++] ddl-files

  1 新建 ddl文件

>vim stud.ddl module  com.xschao.bean {   class Stud{        ustring name;        long id;        int age;        ustring time;        }} 

其他的类型补充，具体是啥自行脑补：

 "\"byte\"",    "\"boolean\"",    "\"int\"",    "\"long\"",    "\"float\"",    "\"double\"",    "\"ustring\"",    "\"buffer\"",    "\"vector\"",    "\"map\"",

2 执行编译命令

> rcc --language java stud.ddl

查看生成的文件：

>tree .|-- com|   `-- xschao|       `-- bean|           `-- Stud.java|-- command_example.sh`-- stud.ddl3 directories, 3 files

Stud.java即为生成的java代码

// File generated by hadoop record compiler. Do not edit.package com.xschao.bean;public class Stud extends org.apache.hadoop.record.Record {  private static final org.apache.hadoop.record.meta.RecordTypeInfo _rio_recTypeInfo;  private static org.apache.hadoop.record.meta.RecordTypeInfo _rio_rtiFilter;  private static int[] _rio_rtiFilterFields;  static {    _rio_recTypeInfo = new org.apache.hadoop.record.meta.RecordTypeInfo("Stud");    _rio_recTypeInfo.addField("name", org.apache.hadoop.record.meta.TypeID.StringTypeID);    _rio_recTypeInfo.addField("id", org.apache.hadoop.record.meta.TypeID.LongTypeID);    _rio_recTypeInfo.addField("age", org.apache.hadoop.record.meta.TypeID.IntTypeID);    _rio_recTypeInfo.addField("time", org.apache.hadoop.record.meta.TypeID.StringTypeID);  }    private String name;  private long id;  private int age;  private String time;  public Stud() { }  public Stud(    final String name,    final long id,    final int age,    final String time) {    this.name = name;    this.id = id;    this.age = age;    this.time = time;  }。。。。。。。。。。。。。。。。。。。。。

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格格巫--蓝精灵-