content: /*
   * 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 com.aliyun.odps.udf;
  
  import java.io.IOException;
  
  /**
   * UDF 基类
   * UDF (User Defined Scalar Function) 自定义函数，其输入输出是一对一的关系，即读入一行数据，写出一条输出值。
   * <p>
   * 自定义 UDF 需要继承这个类来实现一个 UDF，并根据输入输出类型编写 evaluate 方法。
   * </p>
   * 例如:
   * <pre>
   *   public class MyPlus extends UDF {
   *     Long evaluate(Long a, Long b) {
   *       if (a == null || b == null) {
   *         return null;
   *       }
   *       return a + b;
   *     }
   *   }
   * </pre>
   */
  public class UDF implements ContextFunction {
  
    @Override
    public void setup(ExecutionContext ctx) throws UDFException, IOException {
    }
  
    @Override
    public void close() throws UDFException, IOException {
    }
  }
  