com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBAutoGeneratedDefault Maven / Gradle / Ivy

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The AWS SDK for Java with support for OSGi. The AWS SDK for Java provides Java APIs for building software on AWS' cost-effective, scalable, and reliable infrastructure products. The AWS Java SDK allows developers to code against APIs for all of Amazon's infrastructure web services (Amazon S3, Amazon EC2, Amazon SQS, Amazon Relational Database Service, Amazon AutoScaling, etc).

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/*
 * Copyright 2016-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * 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://aws.amazon.com/apache2.0
 *
 * This file 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.amazonaws.services.dynamodbv2.datamodeling;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * Annotation to assign a default value on creation if value is null.
 *
 * A minimal example using getter annotations,
 *  * @DynamoDBTable(tableName="TestTable")
 * public class TestClass {
 *     private String key;
 *     private String status;
 *
 *     @DynamoDBHashKey
 *     public String getKey() { return key; }
 *     public void setKey(String key) { this.key = key; }
 *
 *     @DynamoDBAutoGeneratedDefault("OPEN")
 *     public Sttring getStatus() { return status; }
 *     public void setStatus(String status) { this.status = status; }
 * }
 * 
 *
 * Please note,
 *
 * Only compatible with properties of standard types: {@link String},
 * {@link java.math.BigDecimal}, {@link java.math.BigInteger}, {@link Boolean},
 * {@link Byte}, {@link java.util.Calendar}, {@link Character},
 * {@link java.util.Date}, {@link Double}, {@link Enum}, {@link Float},
 * {@link Integer}, {@link Long}, {@link Short}, and {@link java.util.UUID}.
 */
@DynamoDBAutoGenerated(generator=DynamoDBAutoGeneratedDefault.Generator.class)
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.METHOD})
public @interface DynamoDBAutoGeneratedDefault {

    /**
     * The default value.
     */
    String value();

    /**
     * Default generator.
     */
    static final class Generator implements DynamoDBAutoGenerator {
        private final DynamoDBTypeConverter converter;
        private final String defaultValue;

        public Generator(final Class targetType, final DynamoDBAutoGeneratedDefault annotation) {
            this.converter = StandardTypeConverters.Scalar.STRING.getConverter(targetType);
            this.defaultValue = annotation.value();
        }

        @Override
        public final DynamoDBAutoGenerateStrategy getGenerateStrategy() {
            return DynamoDBAutoGenerateStrategy.CREATE;
        }

        @Override
        public final T generate(final T currentValue) {
            return converter.unconvert(defaultValue);
        }
    }

}