hive添加UDF

hive添加UDF

步骤如下：

  • 函数分为永久和临时函数，后者会话退出则消失，前者不会

  • 查看已有函数（创建好后也可以通过这个来查看是否成功）

show functions;
  • 写UDF的java文件，如：
/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.hive.ql.udf;

import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.hive.serde2.ByteStream;
import org.apache.hadoop.hive.serde2.io.ByteWritable;
import org.apache.hadoop.hive.serde2.io.DoubleWritable;
import org.apache.hadoop.hive.serde2.io.ShortWritable;
import org.apache.hadoop.hive.serde2.io.TimestampWritable;
import org.apache.hadoop.hive.serde2.lazy.LazyInteger;
import org.apache.hadoop.hive.serde2.lazy.LazyLong;
import org.apache.hadoop.io.BooleanWritable;
import org.apache.hadoop.io.BytesWritable;
import org.apache.hadoop.io.FloatWritable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;

/**
 * UDFToString.
 *
 */
public class UDFToString extends UDF {
  private final Text t = new Text();
  private final ByteStream.Output out = new ByteStream.Output();

  public UDFToString() {
  }

  public Text evaluate(NullWritable i) {
    return null;
  }

  private final byte[] trueBytes = {'T', 'R', 'U', 'E'};
  private final byte[] falseBytes = {'F', 'A', 'L', 'S', 'E'};

  public Text evaluate(BooleanWritable i) {
    if (i == null) {
      return null;
    } else {
      t.clear();
      t.set(i.get() ? trueBytes : falseBytes);
      return t;
    }
  }

  public Text evaluate(ByteWritable i) {
    if (i == null) {
      return null;
    } else {
      out.reset();
      LazyInteger.writeUTF8NoException(out, i.get());
      t.set(out.getData(), 0, out.getCount());
      return t;
    }
  }

  public Text evaluate(ShortWritable i) {
    if (i == null) {
      return null;
    } else {
      out.reset();
      LazyInteger.writeUTF8NoException(out, i.get());
      t.set(out.getData(), 0, out.getCount());
      return t;
    }
  }

  public Text evaluate(IntWritable i) {
    if (i == null) {
      return null;
    } else {
      out.reset();
      LazyInteger.writeUTF8NoException(out, i.get());
      t.set(out.getData(), 0, out.getCount());
      return t;
    }
  }

  public Text evaluate(LongWritable i) {
    if (i == null) {
      return null;
    } else {
      out.reset();
      LazyLong.writeUTF8NoException(out, i.get());
      t.set(out.getData(), 0, out.getCount());
      return t;
    }
  }

  public Text evaluate(FloatWritable i) {
    if (i == null) {
      return null;
    } else {
      t.set(i.toString());
      return t;
    }
  }

  public Text evaluate(DoubleWritable i) {
    if (i == null) {
      return null;
    } else {
      t.set(i.toString());
      return t;
    }
  }

  public Text evaluate(Text i) {
      if (i == null) {
          return null;
      }
      i.set(i.toString());
      return i;
  }

  public Text evaluate(TimestampWritable i) {
    if (i == null) {
      return null;
    } else {
      t.set(i.toString());
      return t;
    }
  }

  public Text evaluate (BytesWritable bw) {
    if (null == bw) {
      return null;
}
    t.set(bw.getBytes(),0,bw.getLength());
    return t;
  }
}
  • 将写好的java文件打包成jar：
jar cvf UDFUpper.jar -c bin UDFUpper.java
  • 进入hive，添加jar文件
hive> add jar UDFToString.jar;
Added [UDFToString.jar] to class path
Added resources: [UDFToString.jar]

  • 添加临时函数（会话结束函数消失）

    • 进入hive，添加jar文件

      hive> add jar UDFToString.jar;
Added [UDFToString.jar] to class path
Added resources: [UDFToString.jar]

    • 添加函数(注意class所在包)

      语法为：
CREATE TEMPORARY FUNCTION function_name AS class_name;

hive> create temporary function mytest as 'org.apache.hadoop.hive.ql.udf.UDFToString';
OK
Time taken: 0.009 seconds

路径出错会提示：
FAILED: Class default.udf.Upper not found
FAILED: Execution Error, return code 1 from org.apache.hadoop.hive.ql.exec.FunctionTask

具体类路径为UDF java文件里的package+'.'+java文件名

    • 删除临时函数

      DROP TEMPORARY FUNCTION [IF EXISTS] function_name;

  • 添加永久函数

    • 添加

      语法：
CREATE FUNCTION [db_name.]function_name AS class_name
  [USING JAR|FILE|ARCHIVE 'file_uri' [, JAR|FILE|ARCHIVE 'file_uri'] ];
  
注意：
如果hive非本地模式运行，则后面应该是为非本地文件等URI，如hdfs路径，否则会报错；

例子：
hive> create function default.hah as "org.apache.hadoop.hive.ql.udf.UDFToString" using jar "UDFToString.jar";
FAILED: Execution Error, return code 1 from org.apache.hadoop.hive.ql.exec.FunctionTask. Hive warehouse is non-local, but UDFToString.jar specifies file on local filesystem. Resources on non-local warehouse should specify a non-local scheme/path

hive> create function default.hah as "org.apache.hadoop.hive.ql.udf.UDFToString" using jar "hdfs:///hdfs_home/UDFToString.jar";
converting to local hdfs:///hdfs_home/UDFToString.jar
Added [/tmp/fda83e6d-e1af-4005-affa-9f9c4ee226a6_resources/UDFToString.jar] to class path
Added resources: [hdfs:///hdfs_home/UDFToString.jar]
OK
Time taken: 0.521 seconds

    • 删除

      DROP FUNCTION [IF EXISTS] function_name;
引用第三方包的情况

假如在你的UDF文件里引用了第三方包，那么只需要在生成jar文件的时候改变一下命令就可以了，如下：

javac -classpath hive-0.4.1.jar:commons-io-2.5.jar:bcprov-jdk15on-158.jar  com/example/hive/udf/UDFDecrypt.java

jar -cvf UDFDecrypt.jar ./com/example/hive/udf/UDFDecrypt.class

上面javac命令中classpath跟的是用到的第三方包名，使用：做间隔，后面跟的是java文件路径

此处参考了这里

参考
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原文地址：https://www.cnblogs.com/wswang/p/7718083.html