一、依赖
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>org.example</groupId><artifactId>hivejdbc</artifactId><version>1.0-SNAPSHOT</version><properties><maven.compiler.source>8</maven.compiler.source><maven.compiler.target>8</maven.compiler.target></properties><dependencies><dependency><groupId>org.apache.hive</groupId><artifactId>hive-jdbc</artifactId><version>2.1.1</version><exclusions><exclusion><groupId>org.eclipse.jetty</groupId><artifactId>jetty-runner</artifactId></exclusion></exclusions></dependency><!-- https://mvnrepository.com/artifact/org.apache.hive/hive-exec --><dependency><groupId>org.apache.hive</groupId><artifactId>hive-exec</artifactId><version>3.0.0</version></dependency></dependencies></project>
二、定义类，继承GenericUDF
package cn.edu.tju;
import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDF;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.PrimitiveObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;public class StringLengthUdf extends GenericUDF {@Overridepublic ObjectInspector initialize(ObjectInspector[] objectInspectors) throws UDFArgumentException {return PrimitiveObjectInspectorFactory.javaIntObjectInspector;}@Overridepublic Object evaluate(DeferredObject[] deferredObjects) throws HiveException {String str = deferredObjects[0].get().toString();if(str == null){throw new RuntimeException("空字符串!");}return str.length();}@Overridepublic String getDisplayString(String[] strings) {return "";}
}三、打包jar包
四、上传到hive的服务器
五、通过hive的add jar 添加到hive环境
add jar /root/demo.jar
六、基于jar包创建自定义函数,引号中的是自定义函数类的全路径
create function stringLength as "cn.edu.tju.StringLengthUdf";
七、使用自定义函数：
select stringLength('what is your name?');
)
