自定义函数hello，并注册到hive源码中并重新编译

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1 编写自己的udf方法hello

package cn.zhangjin.hive.udf;

import org.apache.hadoop.hive.ql.exec.Description;

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

import org.apache.hadoop.io.Text;

/**

 * @author zj

 * @create 2019-02-22 17:51

 * 一个UDF: hello

 */

@Description(name = "sayhello",

        value = "_FUNC_(input_str) - returns Hello : input_str ",

        extended = "Example:\n "

                + "  > SELECT _FUNC_('wxk') FROM src LIMIT 1;\n"

                + "  'Hello : wxk'\n")

public class hello extends UDF {

    public Text evaluate(Text input) {

        return new Text("Hello: " + input);

    }

}

pom配置

    <url>http://maven.apache.org</url>

    <properties>

        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

        <hadoop.version>2.6.0-cdh5.7.0</hadoop.version>

        <hive.version>1.1.0-cdh5.7.0</hive.version>

    </properties>

    <repositories>

        <repository>

            <id>cloudera</id>

            <url>https://repository.cloudera.com/artifactory/cloudera-repos</url>

        </repository>

    </repositories>

    <!-- 设定插件仓库 -->

    <pluginRepositories>

        <pluginRepository>

            <id>jeesite-repos</id>

            <name>Jeesite Repository</name>

            <url>http://maven.aliyun.com/nexus/content/groups/public</url>

        </pluginRepository>

    </pluginRepositories>

    <dependencies>

        <dependency>

            <groupId>org.apache.hadoop</groupId>

            <artifactId>hadoop-common</artifactId>

            <version>${hadoop.version}</version>

        </dependency>

        <dependency>

            <groupId>org.apache.hive</groupId>

            <artifactId>hive-exec</artifactId>

            <version>${hive.version}</version>

        </dependency>

        <dependency>

            <groupId>org.apache.hive</groupId>

            <artifactId>hive-jdbc</artifactId>

            <version>${hive.version}</version>

        </dependency>

        <dependency>

            <groupId>junit</groupId>

            <artifactId>junit</artifactId>

            <version>4.10</version>

            <scope>test</scope>

        </dependency>

    </dependencies>

2 下载hive源码

?xml version="1.0" encoding="UTF-8"?

源码下载：http://archive.cloudera.com/cdh5/cdh/5/hive-1.1.0-cdh5.7.0-src.tar.gz

参见：FunctionRegistry

3 自己修改代码

（1）修改udf函数，并放入源码中

将hello.java  放入 hive-1.1.0-cdh5.7.0/ql/src/java/org/apache/hadoop/hive/ql/udf 文件夹中

vi hello.java

将 package com.****.hello; 修改为 package org.apache.hadoop.hive.ql.udf;

（2)修改FunctionRegistry.java 文件

vi hive-1.1.0-cdh5.7.0/ql/src/java/org/apache/hadoop/hive/ql/exec/FunctionRegistry.java

文件头部 一长串 import 下添加，因为我们要吧这个UDF添加进去。

import org.apache.hadoop.hive.ql.udf.hello;

文件头部 static 块中添加  system.registerUDF("hello", hello.class, false);

如下：

static {

    system.registerGenericUDF("concat", GenericUDFConcat.class);

    system.registerUDF("hello", hello.class, false);

    system.registerUDF("substr", UDFSubstr.class, false);

4 重新编译源码

maven install 这里用的idea导入工程进行编译