Hive's custom function and calling Java method through reflect

Homo sapiens 2021-01-22 18:08:12
hive custom function calling java


This blog is about Hive User defined function related content !

First, let's look at the functions that come with the system !

Get into Hive, Enter at the command line show functions;

Find out hive There are nearly a hundred functions that come with it , But we usually use just a few , And its function is very limited ! occasionally , In order to better realize the business requirements , Maybe we need to customize Hive! According to the user-defined function category, it can be divided into the following three types :

(1)UDF(User-Defined-Function) One in, one out (2)UDAF(User-Defined Aggregation Function) Aggregation function , More in one out Be similar to :count/max/min (3)UDTF(User-Defined Table-Generating Functions) One in, many out Such as lateral view explore()

Programming steps :

(1) Inherit org.apache.hadoop.hive.ql.UDF (2) Need to achieve evaluate function ;evaluate Functions support overloading ;

matters needing attention :

(1)UDF There must be a return type , Can return null, But the return type cannot be void; (2)UDF Commonly used Text/LongWritable Other types , It is not recommended to use java type ;

Simple UDF Example

First step : establish maven java engineering , Import jar package

<repositories>
<repository>
<id>cloudera</id>
<url>https://repository.cloudera.com/artifactory/cloudera-repos/</url>
</repository>
</repositories>
<dependencies>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-common</artifactId>
<version>2.6.0-cdh5.14.0</version>
</dependency>
<dependency>
<groupId>org.apache.hive</groupId>
<artifactId>hive-exec</artifactId>
<version>1.1.0-cdh5.14.0</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.0</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>2.2</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<filters>
<filter>
<artifact>*:*</artifact>
<excludes>
<exclude>META-INF/*.SF</exclude>
<exclude>META-INF/*.DSA</exclude>
<exclude>META-INF/*/RSA</exclude>
</excludes>
</filter>
</filters>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>

The second step : Development java Class inheritance UDF, And overloading evaluate Method

public class UDF_01 extends UDF {
// Custom function , Implement uppercase conversion !
public Text evaluate(final Text s){
if (null == s){
return null;
}
// Return capital letters
return new Text(s.toString().toUpperCase());
}
}

The third step : Package our projects , And upload them to linux Under the directory of

Here we will Hive.jar Stored in /opt/hive Under the directory of

Step four : take jar Package is added to the hive stay hive shell Inside add jar route +jar package

Step five : Create temporary functions ( Permanent functions will temporary Delete )

Step six : Call validation

adopt reflect call java Method

After going through the above custom function , I believe you still think the process is a little cumbersome . Never mind , Next, Xiaojun will bring you how to Hive Call in java Method .

First step : Use java Code business logic , And package and upload

public class JAVA_02 {
public static String addInfo(String info){
return info+"__ I love Hive! __ ";
}
}

The second step : take jar Package is added to the hive

The third step : call

select reflect (‘ Parameter one ’,‘ Parameter two ’,‘ Parameter 3 ’)

Parameter one : Package name - Class name Parameter two : Method name Parameter 3 : The data that needs to be calculated

That's all for this sharing , I don't know if the operation is smooth ? In the future, small bacteria will bring you more Hive Highlights of , Coming soon !!!

Participation of this paper Tencent cloud media sharing plan , You are welcome to join us , share .

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https://javamana.com/2021/01/20210122180032355r.html

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