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 org.apache.beam.sdk.schemas;
  
  import java.io.Serializable;
  import org.apache.beam.sdk.transforms.SerializableFunction;
  import org.apache.beam.sdk.values.Row;
  import org.apache.beam.sdk.values.TypeDescriptor;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * Concrete implementations of this class allow creation of schema service objects that vend a
   * {@link Schema} for a specific type. One example use: creating a {@link SchemaProvider} that
   * contacts an external schema-registry service to determine the schema for a type.
   */
  public interface SchemaProvider extends Serializable {
  
    /** Lookup a schema for the given type. If no schema exists, returns null. */
    @Nullable
    <T> Schema schemaFor(TypeDescriptor<T> typeDescriptor);
  
    /**
     * Given a type, return a function that converts that type to a {@link Row} object If no schema
     * exists, returns null.
     */
    @Nullable
    <T> SerializableFunction<T, Row> toRowFunction(TypeDescriptor<T> typeDescriptor);
  
    /**
     * Given a type, returns a function that converts from a {@link Row} object to that type. If no
     * schema exists, returns null.
     */
    @Nullable
    <T> SerializableFunction<Row, T> fromRowFunction(TypeDescriptor<T> typeDescriptor);
  }
  