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

Go to download

Show more of this group Show more artifacts with this name
Show all versions of aws-java-sdk-dynamodb Show documentation

The AWS Java SDK for Amazon DynamoDB module holds the client classes that are used for communicating with Amazon DynamoDB Service

There is a newer version: 1.9.11

Show newest version

/*
 * Copyright 2011-2016 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;
import java.util.Set;

/**
 * Annotation to mark a property as using a custom marshaller. This is required
 * when storing anything other than {@link String}s, {@link Number}s, and
 * {@link Set}s of the same to DynamoDB. Any object that can be converted into a
 * String representation and vice versa can be saved in this manner. This
 * annotation can be applied to either the getter method or the class field for
 * the specific property. If the annotation is applied directly to the class
 * field, the corresponding getter and setter must be declared in the same
 * class.
 * 
 * @see DynamoDBMarshaller
 * @see JsonMarshaller
 */
@DynamoDB
@DynamoDBTypeConverted(converter=DynamoDBMarshalling.Converter.class)
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.METHOD})
public @interface DynamoDBMarshalling {

    /**
     * The class of the Marshaller that converts this property to and from a
     * String.
     */
    Class> marshallerClass();

    /**
     * Marshalling type converter.
     */
    static final class Converter implements DynamoDBTypeConverter {
        private final Class> marshallerClass;
        private final Class targetType;

        public Converter(final Class targetType, final DynamoDBMarshalling annotation) {
            this.marshallerClass = (Class>)annotation.marshallerClass();
            this.targetType = targetType;
        }

        @Override
        public final String convert(final T object) {
            return marshaller().marshall(object);
        }

        @Override
        public final T unconvert(final String object) {
            return marshaller().unmarshall(targetType, object);
        }

        private DynamoDBMarshaller marshaller() {
            try {
                return marshallerClass.newInstance();
            } catch (final Exception e) {
                throw new DynamoDBMappingException("Unable to instantiate marshaller " + marshallerClass, e);
            }
        }
    }
}