HIVE的基本使用05(自定义java函数UDF) demo

maven导入jar包

        cloudera

 https://repository.cloudera.com/artifactory/cloudera-repos/

        org.apache.hadoop

        hadoop-common

        2.6.0-cdh5.14.0

        org.apache.hive

        hive-exec

        1.1.0-cdh5.14.0

        org.apache.maven.plugins

        maven-compiler-plugin

        3.0

            1.8

            1.8

            UTF-8

         org.apache.maven.plugins

         maven-shade-plugin

         2.2

                 package

                     shade

                             *:*

                                 meta-INFRSA

-------------------------------------------主程序代码------------------------------------

package com.cn;

import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.io.Text;


public class UpperFunctionDemo extends UDF {

    
    public Text evaluate(Text text){
        String result = null;
        if (text != null){
            result = text.toString().toUpperCase();
            return new Text(result);
        }else{
            return null;
        }

    }
        
}

----------------------------------java代码编写完成的后续操作-------------------------------

1.将项目打包放到hive的lib目录

2.重命名我们的jar包名称（可有可无，保持包的名字规范即可）

cd /export/servers/hive-1.1.0-cdh5.14.0/lib

mv original-day_06_hive_udf-1.0-SNAPSHOT.jar udf.jar

3.hive的客户端添加我们的jar包

add jar /export/servers/hive-1.1.0-cdh5.14.0/lib/udf.jar;

4.在hive客户端内创建自定义函数，指定对应jar包，以及入口类

create temporary function tolowercase as 'cn.itcast.udf.ItcastUDF';

5.测试自定义函数

select tolowercase('abc');