前言

老版本编写UDF时，需要继承 org.apache.hadoop.hive.ql.exec.UDF类，然后直接实现evaluate()方法即可。
由于公司hive版本比较高（3.x）,这次编写UDF就采用了新的版本，继承类org.apache.hadoop.hive.ql.udf.generic.GenericUDF，实现三个方法

1. 新建项目

打开IDEA，新建一个项目，基本配置如下，Archetype选择图中所示

2.配置maven依赖

导入编写UDF需要用到的依赖

<dependencies><!-- https://mvnrepository.com/artifact/org.apache.hive/hive-exec --><dependency><groupId>org.apache.hive</groupId><artifactId>hive-exec</artifactId><version>3.1.2</version><exclusions><exclusion><groupId>org.apache.commons</groupId><artifactId>commons-compress</artifactId></exclusion></exclusions></dependency>
<build><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><configuration><source>8</source><target>8</target></configuration></plugin></plugins></build>

3.编写代码

目录结构可自行定义，这块不影响实际功能，代码整体框架如下
我这里代码传入三列数据，返回一列数据，入参可以判断一下是否传入数据正确，以及数据类型是否匹配
主要实现三个方法，具体内容在代码块中有说明

1. initialize
2. evaluate
3. getDisplayString

public class ComputeUnitPrice extends GenericUDF {WritableHiveDecimalObjectInspector  decimalObjectInspector;//初始化方法，做一些检查@Overridepublic ObjectInspector initialize(ObjectInspector[] arguments) throws UDFArgumentException {// 判断输入参数的个数if(arguments.length !=3){throw new UDFArgumentLengthException("This UDF Only takes 3 arguments: String, String, Decimal");}ObjectInspector param1 = arguments[0];ObjectInspector param2 = arguments[1];ObjectInspector param3 = arguments[2];// 判断输入参数的类型if(!(param1 instanceof StringObjectInspector)){throw new UDFArgumentException("Param1 Type is error,Must be : String");}if(!(param2 instanceof StringObjectInspector)){throw new UDFArgumentException("Param2 Type is error,Must be : String");}
//        if(!(param3 instanceof JavaConstantHiveDecimalObjectInspector)){
//            throw new UDFArgumentException("Param3 Type is error,Must be : JavaHiveDecimal");
//        }this.decimalObjectInspector = (WritableHiveDecimalObjectInspector ) param3;//函数返回值为 Decimal，需要返回 Decimal类型的鉴别器对象return PrimitiveObjectInspectorFactory.javaHiveDecimalObjectInspector;}
}@Overridepublic Object evaluate(DeferredObject[] arguments) throws HiveException {//计算逻辑编写}//udf的说明@Overridepublic String getDisplayString(String[] children) {return "ComputeUnitPrice";}//main方法测试一下数据结果public static void main(String[] args) throws HiveException {ComputeUnitPrice computeUnitPrice = new ComputeUnitPrice();DeferredObject[] param = {new DeferredJavaObject("箱"), new DeferredJavaObject("800g*8袋/箱"), new DeferredJavaObject(100.20)};JavaDoubleObjectInspector javaDoubleObjectInspector = PrimitiveObjectInspectorFactory.javaDoubleObjectInspector;ObjectInspector stringOi = PrimitiveObjectInspectorFactory.javaStringObjectInspector;ObjectInspector doubleOi = PrimitiveObjectInspectorFactory.javaDoubleObjectInspector;computeUnitPrice.initialize(new ObjectInspector[]{stringOi, stringOi,doubleOi});double res =  javaDoubleObjectInspector.get(computeUnitPrice.evaluate(param));System.out.println("res " + res);}

4.打jar包

将项目打成jar包

mvn clean package

执行完成，target目录下寻找自己的jar包

5.上传服务器

本地上传到机器，再由机器上传到hdfs或者s3等

6.代码中引用

add jars xxxxx/compute_sku_unit_price.jar;
create temporary function compute_sku_unit_price as 'xx.xxx.xxx.xxx.ComputeUnitPrice';
${your_sql};