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.annotation;
  
  import java.lang.annotation.ElementType;
  import java.lang.annotation.Retention;
  import java.lang.annotation.RetentionPolicy;
  import java.lang.annotation.Target;
  
  /**
   * 用于指定{@link com.aliyun.odps.udf.UDTF}的输入输出类型。
   * <p>分别用于指定 {@link com.aliyun.odps.udf.UDTF#process(Object[])} 和 {@link
   * com.aliyun.odps.udf.UDTF#forward(Object[])} 的类型，
   * 语法如下</p>
   * <pre>
   * {@literal @}Resolve({ signature })
   *
   * signature: arg_type_list '->' type_list
   * arg_type_list: type_list | ''
   * type_list: [type_list ','] type
   * type: 'bigint' | 'string' | 'double' | 'boolean'
   * </pre>
   * 比如：
   * <pre>
   * {@literal @}Resolve({"->string"}) // 参数为空，输出一列string字段
   * {@literal @}Resolve({"bigint,boolean->string,double"}) // 参数为bigint,boolean，输出string,double字段
   * </pre>
   */
  @Target({ElementType.TYPE})
  @Retention(RetentionPolicy.RUNTIME)
  public @interface Resolve {
  
    /**
     * 目前只支持数组长度为1的value值。
     */
    String[] value();
  }
  