3）在hive的命令行窗口创建函数

添加jar

add jar jar_path

创建function

create [temporary] function [dbname.]function_name AS class_name;

4）在hive的命令行窗口删除函数

drop [temporary] function [if exists] [dbname.]function_name;

自定义UDF函数

需求：自定义一个UDF函数实现计算字符串长度

（1）创建maven工程

（2）导入依赖

    <dependencies>
        <dependency>
            <groupId>org.apache.hive</groupId>
            <artifactId>hive-exec</artifactId>
            <version>3.1.2</version>
        </dependency>
    </dependencies>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

（3）编写代码

import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.exec.UDFArgumentLengthException;
import org.apache.hadoop.hive.ql.exec.UDFArgumentTypeException;
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.primitive.PrimitiveObjectInspectorFactory;

/**
* 自定义UDF函数需要继承GenericUDF类
* 需求：计算指定字符串的长度
*/
public class MyStringLength extends GenericUDF {
    /**
    * @objectInspectors 输入参数类型的鉴别器对象
    * @return 返回值类型的鉴别器类型对象
    * @throws UDFArgmentException
    */
    public ObjectInspector initialize(ObjectInspector[] objectInspectors) throws UDFArgumentException {
        //判断输入参数的个数
        if (objectInspectors.length != 1) {
            throw new UDFArgumentLengthException("Input args Length Error!!!");
        }
        //判断输入参数的类型
        if (!objectInspectors[0].getCategory().equals(ObjectInspector.Category.PRIMITIVE)) {
            throw new UDFArgumentTypeException(0,"Input Type Error!!!");
        }
        //函数本身返回值为int，需要返回int类型的鉴别器对象
        return PrimitiveObjectInspectorFactory.javaIntObjectInspector;
    }

    /**
     * 函数的逻辑处理
     * @deferredObjects 输入的参数
     * @return 返回值
     * @throws HiveException
     */
    public Object evaluate(DeferredObject[] deferredObjects) throws HiveException {
        if (deferredObjects[0].get() == null) {
            return 0;
        }
        return deferredObjects[0].get().toString().length();
    }

    public String getDisplayString(String[] strings) {
        return null;
    }
}

（4）打包上传到hive

1）打包

2）将包添加到hive

hive (test)> add jar /root/datas/jar/functionlen-1.0-SNAPSHOT.jar;

创建临时函数

hive (test)> create temporary function mylen as "com.zj.MyStringLength";

（5）测试

hive (test)> select name,mylen(name) name_len from movie;

自定义UDTF函数

需求：自定义UDTF函数实现切分字符串

（1）创建maven工程

（2）导入依赖

    <dependencies>
        <dependency>
            <groupId>org.apache.hive</groupId>
            <artifactId>hive-exec</artifactId>
            <version>3.1.2</version>
        </dependency>
    </dependencies>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

（3）编写代码

import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDTF;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorFactory;
import org.apache.hadoop.hive.serde2.objectinspector.StructObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;
import java.util.ArrayList;
import java.util.List;

public class MyUDTF extends GenericUDTF {

    private ArrayList<String> outList = new ArrayList<String>();

    public StructObjectInspector initialize(StructObjectInspector argOIs) throws UDFArgumentException{
        //1.定义输出数据的列名和类型
        List<String> fieldNames = new ArrayList<String>();
        List<ObjectInspector> fieldOTs = new ArrayList<>();
        //2.添加输出数据的列名和类型
        fieldNames.add("lineToWord");
        fieldOTs.add(PrimitiveObjectInspectorFactory.javaStringObjectInspector);

        return ObjectInspectorFactory.getStandardStructObjectInspector(fieldNames,fieldOTs);
    }


    public void process(Object[] objects) throws HiveException {
        //1.获取原始数据
        String object = objects[0].toString();
        //2.获取数据输入的第二个参数，此处为分隔符
        String splitKey = objects[1].toString();
        //3.将原始数据按照传入的分隔符进行切分
        String[] fields = object.split(splitKey);
        //4.遍历切分后的结果，并写出
        for (String field : fields) {
            //清空集合
            outList.clear();
            //将每一个单词添加至集合
            outList.add(field);
            //将集合内容写出
            forward(outList);
        }
    }

    public void close() throws HiveException {

    }
}

（4）打包上传到hive

1）打包

2）将包添加到hive

hive (test)> add jar /root/datas/jar/functionlen-1.0-SNAPSHOT.jar;

创建临时函数

hive (test)> create temporary function myudtf as "com.zj.MyUDTF";

（5）测试

hive (test)> select myudtf("hello,world,hello,hive,hello,spark",",");

本文为学习笔记！！！