HIVE UDF，

HIVE UDF，

项目

MyEclips>New>Java Project>project Name :* trimCharacter *
新建包:package com.tenly.trim;
新建类: trimCharacter
功能实现:去掉数据左右两点

导包

复制:
/hive/lib一级目录下所有包(多余jar包一并复制)
/hadoop/share/hadoop/common/hadoop-common-*.jar
将包加入项目

UDF代码

代码

package com.tenly.trim;
import org.apache.hadoop.hive.ql.exec.UDF;
//继承UDF
public class trimCharacter extends UDF{
//可多个参数
public String evaluate
(String value,String leftCharacter,String rightCharacter)
{
if(value==null || value.length()==0 && 
leftCharacter==null ||leftCharacter.length()==0&&
rightCharacter==null ||rightCharacter.length()==0)
{
       return "";
}else{ 
    String trimValue=value.trim();
    if(trimValue.indexOf(leftCharacter)==0 &&
trimValue.lastIndexOf(rightCharacter)==trimValue.length()-1){
    return trimValue.substring(1, trimValue.length()-1);
   }
 }
    return "";
   }
}

打包

trimCharacter >export>JAR file

上传至Hive节点(非HDFS路径,地址非固定): /usr/local/hive/udf

执行

数据创建,上传HDFS,创建外部表

[root@namenode hadoop]#  `cat  /usr/local/hive/udf/a.txt 
100001  '一个悲催的程序员'
100002  '在写一个悲催的笔记'
100003  '另一个悲催的程序员'
100004  '正在看这篇笔记' 
[root@namenode hadoop]# `hadoop fs -put /usr/local/hive/udf/a.txt  /usr/local/hive/udf`

hive> create external table MyTestUDF(id string , note string) ROW FORMAT DELIMITED FIELDS TERMINATED BY '\t'   LOCATION '/usr/local/hive/udf';

hive> select * from MyTestUDF;
100001  '一个悲催的程序员'
100002  '在写一个悲催的笔记'
100003  '另一个悲催的程序员'
100004  '正在看这篇笔记'

执行UDF三步: 1.加载Jar,2.创建UDF函数,3.使用函数.

hive> add jar /usr/local/hive/udf/trimCharacter.jar
#Added [/usr/local/hive/udf/trimCharacter.jar] to class path
#Added resources: [/usr/local/hive/udf/trimCharacter.jar]

 hive> CREATE TEMPORARY FUNCTION trimCharacter AS 'com.tenly.trim.trimCharacter';

 hive> select id,trimCharacter(note,"'","'")  from MyTestUDF;