flink-libraries/flink-table-common/src/main/java/org/apache/flink/table/factories/TableFactory.java

/*
 * 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.flink.table.factories;

import org.apache.flink.annotation.PublicEvolving;

import java.util.List;
import java.util.Map;

/**
 * A factory to create different table-related instances from string-based properties. This
 * factory is used with Java's Service Provider Interfaces (SPI) for discovering. A factory is
 * called with a set of normalized properties that describe the desired configuration. The factory
 * allows for matching to the given set of properties.
 *
 * <p>Classes that implement this interface can be added to the
 * "META_INF/services/org.apache.flink.table.factories.TableFactory" file of a JAR file in
 * the current classpath to be found.
 *
 * @see TableFormatFactory
 */
@PublicEvolving
public interface TableFactory {

	/**
	 * Specifies the context that this factory has been implemented for. The framework guarantees to
	 * only match for this factory if the specified set of properties and values are met.
	 *
	 * <p>Typical properties might be:
	 *   - connector.type
	 *   - format.type
	 *
	 * <p>Specified property versions allow the framework to provide backwards compatible properties
	 * in case of string format changes:
	 *   - connector.property-version
	 *   - format.property-version
	 *
	 * <p>An empty context means that the factory matches for all requests.
	 */
	Map<String, String> requiredContext();


	/**
	 * List of property keys that this factory can handle. This method will be used for validation.
	 * If a property is passed that this factory cannot handle, an exception will be thrown. The
	 * list must not contain the keys that are specified by the context.
	 *
	 * <p>Example properties might be:
	 *   - schema.#.type
	 *   - schema.#.name
	 *   - connector.topic
	 *   - format.line-delimiter
	 *   - format.ignore-parse-errors
	 *   - format.fields.#.type
	 *   - format.fields.#.name
	 *
	 * <p>Note: Use "#" to denote an array of values where "#" represents one or more digits. Property
	 * versions like "format.property-version" must not be part of the supported properties.
	 *
	 * <p>In some cases it might be useful to declare wildcards "*". Wildcards can only be declared at
	 * the end of a property key.
	 *
	 * <p>For example, if an arbitrary format should be supported:
	 *   - format.*
	 *
	 * <p>Note: Wildcards should be used with caution as they might swallow unsupported properties
	 * and thus might lead to undesired behavior.
	 */
	List<String> supportedProperties();
}