/*
* Copyright 2014-2014 Amazon Technologies, 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://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.marshallers;
import com.amazonaws.services.dynamodbv2.datamodeling.ArgumentMarshaller.StringAttributeMarshaller;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMappingException;
import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMarshaller;
import com.amazonaws.services.dynamodbv2.model.AttributeValue;
/**
* A marshaller that delegates to an instance of a
* {@code DynamoDBMarshalling}-derived custom marshaler.
*/
public class CustomMarshaller implements StringAttributeMarshaller {
private final Class<? extends DynamoDBMarshaller<?>> marshallerClass;
public CustomMarshaller(
Class<? extends DynamoDBMarshaller<?>> marshallerClass) {
this.marshallerClass = marshallerClass;
}
@Override
public AttributeValue marshall(Object obj) {
// TODO: Would be nice to cache this object, but not sure if we can
// do that now without a breaking change; user's marshalers might
// not all be thread-safe.
DynamoDBMarshaller<Object> marshaler =
createMarshaller(marshallerClass);
String stringValue = marshaler.marshall(obj);
if (stringValue == null) {
return null;
} else {
return new AttributeValue(stringValue);
}
}
@SuppressWarnings("unchecked")
private static DynamoDBMarshaller<Object> createMarshaller(Class<?> clazz) {
try {
return (DynamoDBMarshaller<Object>) clazz.newInstance();
} catch (InstantiationException e) {
throw new DynamoDBMappingException(
"Failed to instantiate custom marshaler for class " + clazz,
e);
} catch (IllegalAccessException e) {
throw new DynamoDBMappingException(
"Failed to instantiate custom marshaler for class " + clazz,
e);
}
}
}