自定义UDF函数
1.创建一个Maven工程Hive
2.导入依赖
<dependencies>
<!-- https://mvnrepository.com/artifact/org.apache.hive/hive-exec -->
<dependency>
<groupId>org.apache.hive</groupId>
<artifactId>hive-exec</artifactId>
<version>1.2.1</version>
</dependency>
</dependencies>
3.创建一个类
package com.bigdata.hive;
import org.apache.hadoop.hive.ql.exec.UDF;
public class Lower extends UDF {
public String evaluate (final String s) {
if (s == null) {
return null;
}
return s.toLowerCase();
}
}
4.打成jar包上传到服务器/opt/module/datas/udf.jar
5.将jar包添加到hive的classpath
hive (default)> add jar /opt/module/datas/udf.jar;
6.创建临时函数与开发好的java class关联
hive (default)> create temporary function mylower as "com.bigdata.hive.Lower";
7.即可在hql中使用自定义的函数strip
hive (default)> select ename, mylower(ename) lowername from emp;