com.google.cloud.dataflow.sdk.coders.DefaultCoder Maven / Gradle / Ivy
/*
* Copyright (C) 2015 Google 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 com.google.cloud.dataflow.sdk.coders;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* The {@code DefaultCoder} annotation
* specifies a default {@link Coder} class to handle encoding and decoding
* instances of the annotated class.
*
* The specified {@code Coder} must implement a function with the following
* signature:
*
{@code
* public static Coder of(Class clazz) {...}
* }
*
* For example, to configure the use of Java serialization as the default
* for a class, annotate the class to use
* {@link com.google.cloud.dataflow.sdk.coders.SerializableCoder} as follows:the
*
*
* {@literal @}DefaultCoder(SerializableCoder.class)
* public class MyCustomDataType {
* // ...
* }
*
*
* Similarly, to configure the use of
* {@link com.google.cloud.dataflow.sdk.coders.AvroCoder} as the default:
*
* {@literal @}DefaultCoder(AvroCoder.class)
* public class MyCustomDataType {
* public MyCustomDataType() {} // Avro requires an empty constructor.
* // ...
* }
*
*
* Coders specified explicitly via
* {@link com.google.cloud.dataflow.sdk.values.PCollection#setCoder(Coder)
* PCollection.setCoder}
* take precedence, followed by Coders registered at runtime via
* {@link CoderRegistry#registerCoder}.
*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@SuppressWarnings("rawtypes")
public @interface DefaultCoder {
Class value();
}