io.cdap.wrangler.api.Executor Maven / Gradle / Ivy
/*
* Copyright © 2016-2019 Cask Data, Inc.
*
* Licensed 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 io.cdap.wrangler.api;
import io.cdap.wrangler.api.annotations.PublicEvolving;
import java.io.Serializable;
/**
* A interface defining the wrangle Executor in the wrangling {@link RecipePipeline}.
*
* @param type of input object
* @param type of output object
*/
@PublicEvolving
public interface Executor extends Serializable {
/**
* This method provides a way for the custom directive writer the ability to access
* the arguments passed by the users.
*
* This method is invoked only once during the initialization phase of the {@code Executor}
* object. The arguments are constructed based on the definition as provided by the user in
* the method above {@code define}.
*
*
* Following is an example of how {@code initialize} could be used to accept the
* arguments that are tokenized and parsed by the framework.
*
* public void initialize(Arguments args) throws DirectiveParseException {
* ColumnName column = args.value("column");
* if (args.contains("number") {
* Numeric number = args.value("number");
* }
* Text text = args.value("text");
* Bool bool = args.value("boolean");
* Expression expression = args.value("expression");
* }
*
*
*
* @param args Tokenized and parsed arguments.
* @throws DirectiveParseException thrown by the user in case of any issues with validation or
* ensuring the argument values are as expected.
*/
void initialize(Arguments args) throws DirectiveParseException;
/**
* Executes a wrangle step on single {@link Row} and return an array of wrangled {@link Row}.
*
* @param rows List of input {@link Row} to be wrangled by this step.
* @param context {@link ExecutorContext} passed to each step.
* @return Wrangled List of {@link Row}.
*/
O execute(I rows, ExecutorContext context)
throws DirectiveExecutionException, ErrorRowException, ReportErrorAndProceed;
/**
* This method provides a way for the directive to de-initialize or destroy the
* resources that were acquired during the initialization phase. This method is
* called from the Transform#destroy() when the directive is invoked
* within a plugin or when during Service#destroy() when invoked in the
* service.
*
* This method is specifically designed not to thrown any exceptions. So, if the
* the user code is throws any exception, the system will be unable to react or
* correct at this phase of invocation.
*/
void destroy();
}